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<article article-type="review-article" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink" xml:lang="EN">
<front>
<journal-meta>
<journal-id journal-id-type="publisher-id">Front. Surg.</journal-id>
<journal-title>Frontiers in Surgery</journal-title>
<abbrev-journal-title abbrev-type="pubmed">Front. Surg.</abbrev-journal-title>
<issn pub-type="epub">2296-875X</issn>
<publisher>
<publisher-name>Frontiers Media S.A.</publisher-name>
</publisher>
</journal-meta>
<article-meta>
<article-id pub-id-type="doi">10.3389/fsurg.2024.1211325</article-id>
<article-categories>
<subj-group subj-group-type="heading">
<subject>Surgery</subject>
<subj-group>
<subject>Review</subject>
</subj-group>
</subj-group>
</article-categories>
<title-group>
<article-title>Diagnostic value of procalcitonin in patients with periprosthetic joint infection: a diagnostic meta-analysis</article-title>
</title-group>
<contrib-group>
<contrib contrib-type="author" corresp="yes" equal-contrib="yes"><name><surname>Sun</surname><given-names>Xiaobo</given-names></name>
<xref ref-type="aff" rid="aff1"><sup>1</sup></xref>
<xref ref-type="corresp" rid="cor1">&#x002A;</xref>
<xref ref-type="author-notes" rid="an1"><sup>&#x2020;</sup></xref><uri xlink:href="https://loop.frontiersin.org/people/2291888/overview"/>
</contrib>
<contrib contrib-type="author" equal-contrib="yes"><name><surname>Li</surname><given-names>Yijin</given-names></name>
<xref ref-type="aff" rid="aff2"><sup>2</sup></xref>
<xref ref-type="author-notes" rid="an1"><sup>&#x2020;</sup></xref>
</contrib>
<contrib contrib-type="author" equal-contrib="yes"><name><surname>Lv</surname><given-names>Yan</given-names></name>
<xref ref-type="aff" rid="aff3"><sup>3</sup></xref>
<xref ref-type="author-notes" rid="an1"><sup>&#x2020;</sup></xref>
</contrib>
<contrib contrib-type="author"><name><surname>Liu</surname><given-names>Yuting</given-names></name>
<xref ref-type="aff" rid="aff4"><sup>4</sup></xref>
</contrib>
<contrib contrib-type="author"><name><surname>Lai</surname><given-names>Zhiwei</given-names></name>
<xref ref-type="aff" rid="aff1"><sup>1</sup></xref>
</contrib>
<contrib contrib-type="author"><name><surname>Zeng</surname><given-names>Yirong</given-names></name>
<xref ref-type="aff" rid="aff5"><sup>5</sup></xref><uri xlink:href="https://loop.frontiersin.org/people/2290711/overview" />
</contrib>
<contrib contrib-type="author" corresp="yes"><name><surname>Zhang</surname><given-names>Haitao</given-names></name>
<xref ref-type="aff" rid="aff6"><sup>6</sup></xref>
<xref ref-type="corresp" rid="cor1">&#x002A;</xref>
</contrib>
</contrib-group>
<aff id="aff1"><label><sup>1</sup></label><institution>Department of Orthopaedics, Ganzhou Hospital of Traditional Chinese Medicine</institution>, <addr-line>Ganzhou, Jiangxi</addr-line>, <country>China</country></aff>
<aff id="aff2"><label><sup>2</sup></label><institution>The First Clinical Medical School, Guangzhou University of Chinese Medicine</institution>, <addr-line>Guangzhou, Guangdong</addr-line>, <country>China</country></aff>
<aff id="aff3"><label><sup>3</sup></label><institution>Department of Cardiology, The First Affiliated Hospital of Nanchang University</institution>, <addr-line>Nanchang</addr-line>, <country>China</country></aff>
<aff id="aff4"><label><sup>4</sup></label><institution>Academic Affairs Office, Gannan Medical University</institution>, <addr-line>Ganzhou, Jiangxi</addr-line>, <country>China</country></aff>
<aff id="aff5"><label><sup>5</sup></label><institution>Department of Orthopaedics, The First Affiliated Hospital of Guangzhou University of Chinese Medicine</institution>, <addr-line>Guangzhou, Guangdong</addr-line>, <country>China</country></aff>
<aff id="aff6"><label><sup>6</sup></label><institution>Longhua Hospital, Shanghai University of Traditional Chinese Medicine</institution>, <addr-line>Shanghai</addr-line>, <country>China</country></aff>
<author-notes>
<fn fn-type="edited-by"><p><bold>Edited by:</bold> Jaimo Ahn, University of Michigan, United States</p></fn>
<fn fn-type="edited-by"><p><bold>Reviewed by:</bold> Roberto Berebichez, Centro M&#x00E9;dico ABC, Mexico</p>
<p>Arunika Mukhopadhaya, Indian Institute of Science Education and Research Mohali, India</p></fn>
<corresp id="cor1"><label>&#x002A;</label><bold>Correspondence:</bold> Xiaobo Sun <email>gzsunxiaobo@163.com</email> Haitao Zhang <email>zht1997zht@163.com</email></corresp>
<fn fn-type="equal" id="an1"><label><sup>&#x2020;</sup></label><p>These authors have contributed equally to this work</p></fn>
<fn fn-type="other" id="fn001"><p><bold>Abbreviations</bold> PJI, periprosthetic joint infection; PCT, procalcitonin; PLR, positive likelihood ratio; NLR, negative likelihood ratio; DOR, diagnostic odds ratio; AUC, the area under the summary receiver operating characteristic curve; MSIS, Musculoskeletal Infection Society; ICM, international consensus meeting; CRP, C-reactive protein; ESR, erythrocyte sedimentation rate; WBC, white blood cell; PRISMA, preferred reporting items for systematic reviews and meta-analyses; AAOS, the American Academy of Orthopedic Surgeon.</p></fn>
</author-notes>
<pub-date pub-type="epub"><day>10</day><month>04</month><year>2024</year></pub-date>
<pub-date pub-type="collection"><year>2024</year></pub-date>
<volume>11</volume><elocation-id>1211325</elocation-id>
<history>
<date date-type="received"><day>24</day><month>04</month><year>2023</year></date>
<date date-type="accepted"><day>22</day><month>03</month><year>2024</year></date>
</history>
<permissions>
<copyright-statement>&#x00A9; 2024 Sun, Li, Lv, Liu, Lai, Zeng and Zhang.</copyright-statement>
<copyright-year>2024</copyright-year><copyright-holder>Sun, Li, Lv, Liu, Lai, Zeng and Zhang</copyright-holder><license license-type="open-access" xlink:href="http://creativecommons.org/licenses/by/4.0/">
<p>This is an open-access article distributed under the terms of the <ext-link ext-link-type="uri" xlink:href="http://creativecommons.org/licenses/by/4.0/">Creative Commons Attribution License (CC BY)</ext-link>. The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.</p></license>
</permissions>
<abstract>
<sec><title>Background</title>
<p>The success rate of periprosthetic joint infection (PJI) treatment is still low. Early diagnosis is the key to successful treatment. Therefore, it is necessary to find a biomarker with high sensitivity and specificity. The diagnostic value of serum procalcitonin (PCT) for PJI was systematically evaluated to provide the theoretical basis for clinical diagnosis and treatment in this study.</p>
</sec>
<sec><title>Methods</title>
<p>We searched the Web of Science, Embase, Cochrane Library, and PubMed for studies that evaluated the diagnostic value of serum PCT for PJI (from the inception of each database until September 2020). Two authors independently screened the literature according to the inclusion and exclusion criteria. The quality of each selected literature was evaluated by using the Quality Assessment of Diagnostic Accuracy Studies tool (QUADAS-2) tool. RevMan 5.3 software was used for the quality evaluation. The sensitivity, specificity, positive likelihood ratio (PLR), negative likelihood ratio (NLR), and diagnostic odds ratio (DOR) were merged by using Meta-DiSc 1.4 software. The area under the curve (AUC) and Q index were calculated after the summary receiver operating characteristic (SROC) was generated. We also performed subgroup analysis.</p>
</sec>
<sec><title>Results</title>
<p>A total of 621 patients were enrolled in the nine studies. The pooled sensitivity of serum PCT for PJI diagnosis was 0.441 [95&#x0025; confidence interval (CI), 0.384&#x2013;0.500], the pooled specificity was 0.852 (95&#x0025; CI, 0.811&#x2013;0.888), the pooled PLR was 2.271 (95&#x0025; CI, 1.808&#x2013;2.853), the pooled NLR was 0.713 (95&#x0025; CI, 0.646&#x2013;0.786), and the pooled DOR was 5.756 (95&#x0025; CI, 3.673&#x2013;9.026). The area under SROC (the pooled AUC) was 0.76 (0.72&#x2013;0.79). Q index was 0.6948.</p>
</sec>
<sec><title>Conclusion</title>
<p>This study showed that PCT detection of PJI had poor diagnostic accuracy. Hence, the serum PCT is not suitable as a serum marker for PJI diagnosis.</p>
</sec>
</abstract>
<kwd-group>
<kwd>procalcitonin</kwd>
<kwd>periprosthetic joint infection</kwd>
<kwd>diagnosis</kwd>
<kwd>biological markers</kwd>
<kwd>meta-analysis</kwd>
</kwd-group>
<counts>
<fig-count count="10"/>
<table-count count="3"/><equation-count count="0"/><ref-count count="53"/><page-count count="0"/><word-count count="0"/></counts><custom-meta-wrap><custom-meta><meta-name>section-at-acceptance</meta-name><meta-value>Orthopedic Surgery</meta-value></custom-meta></custom-meta-wrap>
</article-meta>
</front>
<body>
<sec id="s1" sec-type="intro"><title>Introduction</title>
<p>Periprosthetic joint infection (PJI) is one of the catastrophic complications after total joint arthroplasty (<xref ref-type="bibr" rid="B1">1</xref>). The incidence of PJI after total knee arthroplasty (TKA) was 0.7&#x0025; (<xref ref-type="bibr" rid="B2">2</xref>). The total hip arthroplasty (THA) infection incidence was 1.63&#x0025; within 2 years and 0.59&#x0025; between 2 and 10 years (<xref ref-type="bibr" rid="B3">3</xref>). PJI is the second reason for the early revision of THA (<xref ref-type="bibr" rid="B4">4</xref>). It may result in reduced knee or hip function and reduced quality of life for patients, as well as the failure of the implant and the need for revision arthroplasty (<xref ref-type="bibr" rid="B5">5</xref>).</p>
<p>Currently, the diagnosis for PJI depends mainly on the guidelines of the American Academy of Orthopedic Surgeon (AAOS)&#x0027;s guidelines the Infectious Diseases Society of America (IDSA), the Musculoskeletal Infection Society (MSIS) criteria of 2011 and 2018, the European Bone and Joint Infection Society (EBJIS) definition, a large number of biomarkers [white blood cell (WBC), C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), synovial fluid], pathologic examinations and preoperative aspirations (<xref ref-type="bibr" rid="B6">6</xref>&#x2013;<xref ref-type="bibr" rid="B10">10</xref>). Unfortunately, the effectiveness of WBC in diagnosing PJI is limited (<xref ref-type="bibr" rid="B11">11</xref>, <xref ref-type="bibr" rid="B12">12</xref>). CRP and ESR present high sensitivity and low specificity. We determine the diagnosis according to intraoperative pathologic examination with the lack of typical symptoms. It is difficult to accurately diagnose PJI before surgery, and it is a research hotspot to find specific serum markers such as interleukin-6, procalcitonin (PCT), and &#x03B1;-defensin (<xref ref-type="bibr" rid="B13">13</xref>).</p>
<p>PCT is a protein containing 116 amino acids produced by neuroendocrine cells and parafollicular thyroid gland cells (<xref ref-type="bibr" rid="B14">14</xref>). Serum PCT levels in uninfected healthy people are low but significantly increase in severe bacterial and fungal infections (<xref ref-type="bibr" rid="B15">15</xref>). Aseptic infections such as multiple organ failure and extensive burns are common causes of elevated serum calcitonin. It has been reported that injection of bacterial endotoxin into healthy people can induce the release of systemic PCT. The PCT test has high diagnostic accuracy in identifying systemic infection (<xref ref-type="bibr" rid="B14">14</xref>, <xref ref-type="bibr" rid="B16">16</xref>, <xref ref-type="bibr" rid="B17">17</xref>). However, different scholars have drawn entirely different conclusions regarding PCT diagnosis for PJI. Therefore, we performed a systematic review and meta-analysis to evaluate the diagnostic value of PCT in PJI.</p>
</sec>
<sec id="s2" sec-type="methods"><title>Materials and methods</title>
<p>Our study was strictly performed on the basis of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines (<xref ref-type="bibr" rid="B18">18</xref>). All authors participated in formulating the literature retrieval scheme. We finished the work in an orderly fashion.</p>
<sec id="s2a"><title>Data and literature sources</title>
<p>We searched the Web of Science, Embase, Cochrane Library, and PubMed for studies that evaluated the diagnostic value of PCT for PJI (from the inception of each database until September 2020). There was no language limit. The search strategy follows the combination of subject terms and accessible terms. The search subject words and free words are as follows: &#x201C;prosthesis-related infections&#x201D; or &#x201C;Prosthesis Related Infections&#x201D; or &#x201C;Infections, Prosthesis-Related&#x201D; or &#x201C;Prosthesis-Related Infection&#x201D; or &#x201C;Prosthetic joint infection&#x201D; or &#x201C;Prosthesis joint infection&#x201D; or &#x201C;PJI&#x201D; stands for disease, &#x201C;Procalcitonin&#x201D; or &#x201C;Calcitonin Precursor Polyprotein&#x201D; or &#x201C;Calcitonin-1&#x201D; or &#x201C;Calcitonin 1&#x201D; or &#x201C;Calcitonin Related Polypeptide Alpha&#x201D; or &#x201C;Pro-Calcitonin&#x201D; or &#x201C;PCT&#x201D; represents target index. After electronic research, additional related studies in the literature were added by manual retrieval.</p>
</sec>
<sec id="s2b"><title>Study selection</title>
<p>The included studies meet the following criteria: (1) Serum PCT was used to diagnose PJI; (2) The type of study is retrospective or prospective analysis; and (3) We can indirectly or directly obtain a 2&#x2009;&#x00D7;&#x2009;2 table of PCT diagnosis for PJI; (4) The source of samples for the research is clear; and (5) The reference standard for the diagnosis of PJI is described in the literature. The following studies were excluded: (1) When we could not obtain the necessary 2&#x2009;&#x00D7;&#x2009;2 table data through calculating or contacting the author; (2) When patients suffered extra-articular infection of joint; (3) When the review literature, special case reports, animal experiments, and repeated reports were missing; (4) When the detection methods for PCT have not been used in clinical examination or have been eliminated; and (5) When the patients were in a poor nutritional state. Two authors reviewed the title, abstract, and full texts independently. The third author resolved the disagreements between the first two reviewers and made a final decision.</p>
</sec>
<sec id="s2c"><title>Data extraction and quality assessment</title>
<p>Two authors independently screened the literature according to the inclusion and exclusion criteria and entered the extracted data into a table. The recorded baseline data and outcome indicators were as follows: Author, year, country, study type, gender, median age, and body mass index (BMI), detection method, threshold value, gold standard, operative site, total staff, PJI number, N-PJI number, SN (sensitivity), SP (specificity), TP (true positive), FP (false positive), FN (false negative), and TN (true negative). SN, SP, TP, and FP data were built into a 2&#x2009;&#x00D7;&#x2009;2 table.</p>
<p>We used the Quality Assessment of Diagnostic Accuracy Studies tool (QUADAS-2) to evaluate the quality of each selected literature (<xref ref-type="bibr" rid="B19">19</xref>). QUADAS-2 was adopted to evaluate the literature along four significant aspects (patient selection, diagnostic test, gold standard, and loss of follow-up). We have assessed the risk of bias in the four aspects and the clinical utility of the first three aspects. RevMan 5.3 software was used for the evaluation of quality.</p>
</sec>
<sec id="s2d"><title>Data synthesis and analysis</title>
<p>We combined TP, FP, FN, and TN extracted from the literature, and obtained the SN, SP, positive likelihood ratio (PLR), negative likelihood ratio (NLR), and DOR using Meta-DiSc 1.4 software. Whether it is a PLR or an NLR, the further away from 1 it is, the more meaningful it becomes. A PLR greater than 10 means that a positive test is very effective in diagnosing the disease. An NLR less than 0.1 means that a negative test is very effective in ruling out the diagnosis (<xref ref-type="bibr" rid="B20">20</xref>). The higher the DOR, the better the diagnostic value (<xref ref-type="bibr" rid="B21">21</xref>). In addition, the area under the curve (AUC) and Q index were calculated after the summary receiver operating characteristic (SROC) was generated. An AUC value (greater than 0.8) shows good diagnostic accuracy of PCT.</p>
<p>In diagnostic meta-analysis, both the threshold effect and the non-threshold product can cause heterogeneity. Suppose there is a negative correlation between SN and SP (or a positive correlation between SN and 1&#x2009;&#x2212;&#x2009;SP), and there is a &#x201C;shoulder-arm&#x201D; point distribution on the receiver operating characteristic (ROC) curve graph. In that case, it can be judged that there is a threshold effect. When the threshold effect causes heterogeneity, Spearman correlation analysis is used. When the heterogeneity is caused by the non-threshold effect, the chi-square test is used to analyze the heterogeneity among the study results, and the inconsistency index (<italic>I</italic><sup>2</sup>) is used as the quantitative judgment for the heterogeneity size. The greater the value of <italic>I</italic><sup>2</sup> expressed, the greater the value of the heterogeneity, and vice versa. <italic>I</italic><sup>2</sup> values of 25&#x0025;, 50&#x0025;, and 75&#x0025;, respectively, represent low, moderate, and high heterogeneity. If the heterogeneity of multiple independent studies is low, the fixed-effect model can be selected. If the heterogeneity is high, the random effect model can be selected. Meta-regression and subgroup (Study design, Threshold value, MSIS, East Asian race) analysis are conducted to investigate the source of heterogeneity. When the heterogeneity is still high after heterogeneity analysis and treatment, we use Stata 14.0 software to draw Deeks&#x2019; funnel plot and evaluate the publication bias (<xref ref-type="bibr" rid="B22">22</xref>).</p>
</sec>
</sec>
<sec id="s3" sec-type="results"><title>Results</title>
<sec id="s3a"><title>Identification of studies</title>
<p>The literature screening flow diagram is detailed in <xref ref-type="fig" rid="F1">Figure&#x00A0;1</xref>. A total of 46 references were obtained in the preliminary search in four online databases (Web of Science, Embase, Cochrane Library, PubMed). Seven additional records were identified through other sources. After removing 26 duplicates, 27 studies remained; of these, 12 articles were excluded based on the title and/or abstract, and five articles were excluded by reading their full text. One literature with qualitative synthesis was excluded. In the end, only nine studies were left for meta-analysis (<xref ref-type="bibr" rid="B14">14</xref>, <xref ref-type="bibr" rid="B23">23</xref>&#x2013;<xref ref-type="bibr" rid="B30">30</xref>).</p>
<fig id="F1" position="float"><label>Figure 1</label>
<caption><p>PRISMA flow diagram.</p></caption>
<graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="fsurg-11-1211325-g001.tif"/>
</fig>
</sec>
<sec id="s3b"><title>Study characteristics and patient samples</title>
<p>Three studies (<xref ref-type="bibr" rid="B14">14</xref>, <xref ref-type="bibr" rid="B23">23</xref>, <xref ref-type="bibr" rid="B26">26</xref>) were from East Asia and six (<xref ref-type="bibr" rid="B24">24</xref>, <xref ref-type="bibr" rid="B25">25</xref>, <xref ref-type="bibr" rid="B27">27</xref>&#x2013;<xref ref-type="bibr" rid="B30">30</xref>) from other countries. Two retrospective studies (<xref ref-type="bibr" rid="B23">23</xref>, <xref ref-type="bibr" rid="B25">25</xref>) and seven prospective studies (<xref ref-type="bibr" rid="B14">14</xref>, <xref ref-type="bibr" rid="B24">24</xref>, <xref ref-type="bibr" rid="B26">26</xref>&#x2013;<xref ref-type="bibr" rid="B30">30</xref>) were included. Totally 621 patients were enrolled in the nine studies (<xref ref-type="bibr" rid="B14">14</xref>, <xref ref-type="bibr" rid="B23">23</xref>&#x2013;<xref ref-type="bibr" rid="B30">30</xref>), including 385 women and 236 men. The average age ranged from 62 to 72 years. BMI values were not available in four studies (<xref ref-type="bibr" rid="B23">23</xref>, <xref ref-type="bibr" rid="B25">25</xref>, <xref ref-type="bibr" rid="B27">27</xref>, <xref ref-type="bibr" rid="B29">29</xref>), and those that were available in the five other studies (<xref ref-type="bibr" rid="B14">14</xref>, <xref ref-type="bibr" rid="B24">24</xref>, <xref ref-type="bibr" rid="B26">26</xref>, <xref ref-type="bibr" rid="B28">28</xref>, <xref ref-type="bibr" rid="B30">30</xref>) ranged from 26.7 to 30&#x2005;kg/m<sup>2</sup>. The detection method was not found in the study (<xref ref-type="bibr" rid="B23">23</xref>). The threshold is 0.5&#x2005;ng/ml in four studies (<xref ref-type="bibr" rid="B14">14</xref>, <xref ref-type="bibr" rid="B24">24</xref>, <xref ref-type="bibr" rid="B26">26</xref>, <xref ref-type="bibr" rid="B29">29</xref>). MSIS is the &#x201C;gold standard&#x201D; for diagnosis in four studies (<xref ref-type="bibr" rid="B23">23</xref>, <xref ref-type="bibr" rid="B25">25</xref>, <xref ref-type="bibr" rid="B27">27</xref>, <xref ref-type="bibr" rid="B28">28</xref>). All the studies included patients who underwent hip or knee arthroplasty, and only one study (<xref ref-type="bibr" rid="B24">24</xref>) included patients who underwent shoulder arthroplasty. The basic characteristics of the included studies are provided in <xref ref-type="table" rid="T1">Table&#x00A0;1</xref>. <xref ref-type="table" rid="T2">Table&#x00A0;2</xref> summarizes the basic data extracted from each study (2&#x2009;&#x00D7;&#x2009;2 table).</p>
<table-wrap id="T1" position="float"><label>Table 1</label>
<caption><p>Characteristics of the studies in meta-analysis for the diagnosis of PJI applying serum procalcitonin.</p></caption>
<table frame="hsides" rules="groups">
<colgroup>
<col align="left"/>
<col align="left"/>
<col align="left"/>
<col align="left"/>
<col align="left"/>
<col align="left"/>
<col align="left"/>
<col align="left"/>
<col align="left"/>
<col align="left"/>
<col align="left"/>
</colgroup>
<thead>
<tr>
<th valign="top" align="left">Authors</th>
<th valign="top" align="center">Year</th>
<th valign="top" align="center">Country</th>
<th valign="top" align="center">Study type</th>
<th valign="top" align="center">Gender (F/M)</th>
<th valign="top" align="center">Median age (N/PJI)</th>
<th valign="top" align="center">BMI (N/PJI)</th>
<th valign="top" align="center">Detection method</th>
<th valign="top" align="center">Threshold value (ng/ml)</th>
<th valign="top" align="center">Gold standard<xref ref-type="table-fn" rid="table-fn2"><sup>a</sup></xref></th>
<th valign="top" align="center">Operative site</th>
</tr>
</thead>
<tbody>
<tr>
<td valign="top" align="left">Bottner et al. (<xref ref-type="bibr" rid="B30">30</xref>)</td>
<td valign="top" align="center">2007</td>
<td valign="top" align="left">Germany</td>
<td valign="top" align="left">P</td>
<td valign="top" align="center">37/41</td>
<td valign="top" align="center">64</td>
<td valign="top" align="center">28.3/28</td>
<td valign="top" align="left">Krypto PCT</td>
<td valign="top" align="center">0.3</td>
<td valign="top" align="left">MSIS</td>
<td valign="top" align="left">Hip or knee</td>
</tr>
<tr>
<td valign="top" align="left">Worthington et al. (<xref ref-type="bibr" rid="B29">29</xref>)</td>
<td valign="top" align="center">2010</td>
<td valign="top" align="left">UK</td>
<td valign="top" align="left">P</td>
<td valign="top" align="center">25/21</td>
<td valign="top" align="center">72</td>
<td valign="top" align="center">NA.</td>
<td valign="top" align="left">BRAHMS PCT-Q kits</td>
<td valign="top" align="center">0.5</td>
<td valign="top" align="left">MSIS</td>
<td valign="top" align="left">Hip</td>
</tr>
<tr>
<td valign="top" align="left">Glehr et al. (<xref ref-type="bibr" rid="B28">28</xref>)</td>
<td valign="top" align="center">2013</td>
<td valign="top" align="left">Austria</td>
<td valign="top" align="left">P</td>
<td valign="top" align="center">38/46</td>
<td valign="top" align="center">65/66</td>
<td valign="top" align="center">30</td>
<td valign="top" align="left">Elecsys BRAHMS PCT kits</td>
<td valign="top" align="center">0.35</td>
<td valign="top" align="left">MSIS</td>
<td valign="top" align="left">Hip or knee</td>
</tr>
<tr>
<td valign="top" align="left">Randau et al. (<xref ref-type="bibr" rid="B27">27</xref>)</td>
<td valign="top" align="center">2014</td>
<td valign="top" align="left">Germany</td>
<td valign="top" align="left">P</td>
<td valign="top" align="center">73/47</td>
<td valign="top" align="center">67.94</td>
<td valign="top" align="center">NA</td>
<td valign="top" align="left">Immunoassay Analyzer</td>
<td valign="top" align="center">46</td>
<td valign="top" align="left">MSIS</td>
<td valign="top" align="left">Hip or knee</td>
</tr>
<tr>
<td valign="top" align="left">Yuan et al. (<xref ref-type="bibr" rid="B26">26</xref>)</td>
<td valign="top" align="center">2015</td>
<td valign="top" align="left">China</td>
<td valign="top" align="left">P</td>
<td valign="top" align="center">49/22</td>
<td valign="top" align="center">62/67</td>
<td valign="top" align="center">28.4/29.2</td>
<td valign="top" align="left">Immunochromatography</td>
<td valign="top" align="center">0.5</td>
<td valign="top" align="left">ICM</td>
<td valign="top" align="left">Hip</td>
</tr>
<tr>
<td valign="top" align="left">Yildirim et al. (<xref ref-type="bibr" rid="B25">25</xref>)</td>
<td valign="top" align="center">2017</td>
<td valign="top" align="left">Turkey</td>
<td valign="top" align="left">R</td>
<td valign="top" align="center">75/10</td>
<td valign="top" align="center">68.2</td>
<td valign="top" align="center">NA</td>
<td valign="top" align="left">The ELISA kits ab100630</td>
<td valign="top" align="center">0.081</td>
<td valign="top" align="left">MSIS</td>
<td valign="top" align="left">Knee</td>
</tr>
<tr>
<td valign="top" align="left">Sa-ngasoongsong et al. (<xref ref-type="bibr" rid="B14">14</xref>)</td>
<td valign="top" align="center">2018</td>
<td valign="top" align="left">Thailand</td>
<td valign="top" align="left">P</td>
<td valign="top" align="center">25/7</td>
<td valign="top" align="center">68</td>
<td valign="top" align="center">26.9</td>
<td valign="top" align="left">Enzyme immunoassay kit</td>
<td valign="top" align="center">0.5</td>
<td valign="top" align="left">ICM</td>
<td valign="top" align="left">Hip or knee</td>
</tr>
<tr>
<td valign="top" align="left">Busch et al. (<xref ref-type="bibr" rid="B24">24</xref>)</td>
<td valign="top" align="center">2020</td>
<td valign="top" align="left">Germany</td>
<td valign="top" align="left">P</td>
<td valign="top" align="center">42/28</td>
<td valign="top" align="center">66 /72</td>
<td valign="top" align="center">26.7/27.1</td>
<td valign="top" align="left">Enzyme immunoassays</td>
<td valign="top" align="center">0.5</td>
<td valign="top" align="left">MSIS</td>
<td valign="top" align="left">Hip or knee or shoulder</td>
</tr>
<tr>
<td valign="top" align="left">Chu et al. (<xref ref-type="bibr" rid="B23">23</xref>)</td>
<td valign="top" align="center">2020</td>
<td valign="top" align="left">China</td>
<td valign="top" align="left">R</td>
<td valign="top" align="center">21/14</td>
<td valign="top" align="center">65/66</td>
<td valign="top" align="center">NA</td>
<td valign="top" align="left">NA</td>
<td valign="top" align="center">NA</td>
<td valign="top" align="left">MSIS</td>
<td valign="top" align="left">Hip or knee</td>
</tr>
</tbody>
</table>
<table-wrap-foot>
<fn id="table-fn1"><p>P, prospective study; R, retrospective study; NA, not applicable; N, non-PJI; Krypto PCT, time-resolved amplified cryptate emission (TRACE) technology assay; MSIS, musculoskeletal Infection Society; ICM, international consensus on infection.</p></fn>
<fn id="table-fn2"><label><sup>a</sup></label><p>Gold standard refers to the diagnostic PJI reference standard, which under the current study was considered to be 100&#x0025; diagnostic accuracy.</p></fn>
</table-wrap-foot>
</table-wrap>
<table-wrap id="T2" position="float"><label>Table 2</label>
<caption><p>Data extracted for the construction of 2&#x2009;&#x00D7;&#x2009;2 table.</p></caption>
<table frame="hsides" rules="groups">
<colgroup>
<col align="left"/>
<col align="center"/>
<col align="center"/>
<col align="center"/>
<col align="center"/>
<col align="center"/>
<col align="center"/>
<col align="center"/>
<col align="center"/>
<col align="center"/>
<col align="center"/>
</colgroup>
<thead>
<tr>
<th valign="top" align="left">Authors</th>
<th valign="top" align="center">Year</th>
<th valign="top" align="center">Total participants</th>
<th valign="top" align="center">PJI</th>
<th valign="top" align="center">N-PJI</th>
<th valign="top" align="center">SN (&#x0025;)</th>
<th valign="top" align="center">SP (&#x0025;)</th>
<th valign="top" align="center">TP</th>
<th valign="top" align="center">FP</th>
<th valign="top" align="center">FN</th>
<th valign="top" align="center">TN</th>
</tr>
</thead>
<tbody>
<tr>
<td valign="top" align="left">Bottner et al. (<xref ref-type="bibr" rid="B30">30</xref>)</td>
<td valign="top" align="center">2007</td>
<td valign="top" align="center">78</td>
<td valign="top" align="center">21</td>
<td valign="top" align="center">57</td>
<td valign="top" align="center">33&#x0025;</td>
<td valign="top" align="center">98&#x0025;</td>
<td valign="top" align="center">7</td>
<td valign="top" align="center">1</td>
<td valign="top" align="center">14</td>
<td valign="top" align="center">56</td>
</tr>
<tr>
<td valign="top" align="left">Worthington et al. (<xref ref-type="bibr" rid="B29">29</xref>)</td>
<td valign="top" align="center">2010</td>
<td valign="top" align="center">46</td>
<td valign="top" align="center">16</td>
<td valign="top" align="center">30</td>
<td valign="top" align="center">6.25</td>
<td valign="top" align="center">100</td>
<td valign="top" align="center">1</td>
<td valign="top" align="center">0</td>
<td valign="top" align="center">15</td>
<td valign="top" align="center">30</td>
</tr>
<tr>
<td valign="top" align="left">Glehr et al. (<xref ref-type="bibr" rid="B28">28</xref>)</td>
<td valign="top" align="center">2013</td>
<td valign="top" align="center">84</td>
<td valign="top" align="center">55</td>
<td valign="top" align="center">29</td>
<td valign="top" align="center">80</td>
<td valign="top" align="center">37</td>
<td valign="top" align="center">44</td>
<td valign="top" align="center">18</td>
<td valign="top" align="center">11</td>
<td valign="top" align="center">11</td>
</tr>
<tr>
<td valign="top" align="left">Randau et al. (<xref ref-type="bibr" rid="B27">27</xref>)</td>
<td valign="top" align="center">2014</td>
<td valign="top" align="center">120</td>
<td valign="top" align="center">48</td>
<td valign="top" align="center">72</td>
<td valign="top" align="center">12.9</td>
<td valign="top" align="center">100</td>
<td valign="top" align="center">6</td>
<td valign="top" align="center">0</td>
<td valign="top" align="center">42</td>
<td valign="top" align="center">72</td>
</tr>
<tr>
<td valign="top" align="left">Yuan et al. (<xref ref-type="bibr" rid="B26">26</xref>)</td>
<td valign="top" align="center">2015</td>
<td valign="top" align="center">71</td>
<td valign="top" align="center">25</td>
<td valign="top" align="center">46</td>
<td valign="top" align="center">80</td>
<td valign="top" align="center">74</td>
<td valign="top" align="center">20</td>
<td valign="top" align="center">12</td>
<td valign="top" align="center">5</td>
<td valign="top" align="center">34</td>
</tr>
<tr>
<td valign="top" align="left">Yildirim et al. (<xref ref-type="bibr" rid="B25">25</xref>)</td>
<td valign="top" align="center">2017</td>
<td valign="top" align="center">80</td>
<td valign="top" align="center">45</td>
<td valign="top" align="center">40</td>
<td valign="top" align="center">80</td>
<td valign="top" align="center">60</td>
<td valign="top" align="center">36</td>
<td valign="top" align="center">16</td>
<td valign="top" align="center">9</td>
<td valign="top" align="center">24</td>
</tr>
<tr>
<td valign="top" align="left">Sa-ngasoongsong et al. (<xref ref-type="bibr" rid="B14">14</xref>)</td>
<td valign="top" align="center">2018</td>
<td valign="top" align="center">32</td>
<td valign="top" align="center">20</td>
<td valign="top" align="center">12</td>
<td valign="top" align="center">40</td>
<td valign="top" align="center">100</td>
<td valign="top" align="center">8</td>
<td valign="top" align="center">0</td>
<td valign="top" align="center">12</td>
<td valign="top" align="center">12</td>
</tr>
<tr>
<td valign="top" align="left">Busch et al. (<xref ref-type="bibr" rid="B24">24</xref>)</td>
<td valign="top" align="center">2020</td>
<td valign="top" align="center">70</td>
<td valign="top" align="center">23</td>
<td valign="top" align="center">47</td>
<td valign="top" align="center">13</td>
<td valign="top" align="center">91</td>
<td valign="top" align="center">3</td>
<td valign="top" align="center">4</td>
<td valign="top" align="center">20</td>
<td valign="top" align="center">43</td>
</tr>
<tr>
<td valign="top" align="left">Chu et al. (<xref ref-type="bibr" rid="B23">23</xref>)</td>
<td valign="top" align="center">2020</td>
<td valign="top" align="center">35</td>
<td valign="top" align="center">16</td>
<td valign="top" align="center">19</td>
<td valign="top" align="center">46</td>
<td valign="top" align="center">95</td>
<td valign="top" align="center">7</td>
<td valign="top" align="center">1</td>
<td valign="top" align="center">39</td>
<td valign="top" align="center">18</td>
</tr>
</tbody>
</table>
<table-wrap-foot>
<fn id="table-fn3"><p>N-PJI, non-PJI.</p></fn>
</table-wrap-foot>
</table-wrap>
</sec>
<sec id="s3c"><title>Quality and publication biases of the included studies</title>
<p>The methodological quality of the studies was assessed by using the QUADAS-2 tool (<xref ref-type="fig" rid="F2">Figure&#x00A0;2</xref>). There is one &#x201C;high risk&#x201D; for patient selection, which is shown in the figure (<xref ref-type="bibr" rid="B25">25</xref>). Generally speaking, the quality of the included studies was satisfactory. As mentioned previously, Deeks&#x2019; test was used to analyze the publication bias of the nine included studies. The Stata command for publication bias in diagnostic meta is &#x201C;midas tp fp fn tn, pubbias&#x201D;. As shown in <xref ref-type="fig" rid="F3">Figure&#x00A0;3</xref>, the funnel plot is roughly symmetric (<italic>P</italic>&#x2009;&#x003D;&#x2009;0.61). Therefore, there was no significant bias in publication.</p>
<fig id="F2" position="float"><label>Figure 2</label>
<caption><p>Quality assessment of included studies based on QUADAS-2 tool criteria.</p></caption>
<graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="fsurg-11-1211325-g002.tif"/>
</fig>
<fig id="F3" position="float"><label>Figure 3</label>
<caption><p>Funnel plot for publication bias assessment of included studies.</p></caption>
<graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="fsurg-11-1211325-g003.tif"/>
</fig>
</sec>
<sec id="s3d"><title>Threshold and diagnostic accuracy of PCT for PJI</title>
<p>The data were imported into the Meta-DiSc 1.4 software for analysis. The Spearman correlation coefficient between the logarithm of SN and 1&#x2009;&#x2212;&#x2009;SP was 0.729 (<italic>P&#x2009;</italic>&#x003D;&#x2009;0.026). The result was significant, indicating a threshold effect in this study. Furthermore, a &#x201C;shoulder-arm&#x201D; point distribution on the SROC curve graph was drawn symmetrically. It also demonstrated the threshold effects of this study. The heterogeneity might be related to the threshold effects.</p>
<p>The value of Cochran&#x2019;s Q was 10.21 in the DOR graph (<italic>P</italic>&#x2009;&#x003D;&#x2009;0.250, <italic>P</italic>&#x2009;&#x003E;&#x2009;0.001). In other words, no heterogeneity was caused by a non-threshold effect in this study. Furthermore, the <italic>I</italic><sup>2</sup> statistics for DOR, SN, SP, PLR, and NLR were 21.6&#x0025;, 93.9&#x0025;, 92.3&#x0025;, 64.2&#x0025;, and 85.1&#x0025;, respectively. Therefore, we used the fixed-effect model to combine the aforementioned five effects.</p>
<p>The pooled SN of PCT for PJI diagnosis was 0.441 [95&#x0025; confidence interval (CI), 0.384&#x2013;0.500] (<xref ref-type="fig" rid="F4">Figure&#x00A0;4</xref>), the pooled SP was 0.852 (95&#x0025; CI, 0.811&#x2013;0.888) (<xref ref-type="fig" rid="F5">Figure&#x00A0;5</xref>), the pooled PLR was 2.271 (95&#x0025; CI, 1.808&#x2013;2.853) (<xref ref-type="fig" rid="F6">Figure&#x00A0;6</xref>), the pooled NLR was 0.713 (95&#x0025; CI, 0.646&#x2013;0.786) (<xref ref-type="fig" rid="F7">Figure&#x00A0;7</xref>), and the pooled DOR was 5.756 (95&#x0025; CI, 3.673&#x2013;9.026) (<xref ref-type="fig" rid="F8">Figure&#x00A0;8</xref>). The area under SROC (the pooled AUC) was 0.76 (0.72&#x2013;0.79) (<xref ref-type="fig" rid="F9">Figure&#x00A0;9A</xref>). Q index was 0.6948 (<xref ref-type="fig" rid="F9">Figure&#x00A0;9B</xref>).</p>
<fig id="F4" position="float"><label>Figure 4</label>
<caption><p>Forest plot of pooled sensitivity.</p></caption>
<graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="fsurg-11-1211325-g004.tif"/>
</fig>
<fig id="F5" position="float"><label>Figure 5</label>
<caption><p>Forest plot of pooled specificity.</p></caption>
<graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="fsurg-11-1211325-g005.tif"/>
</fig>
<fig id="F6" position="float"><label>Figure 6</label>
<caption><p>Forest plot of pooled PLR.</p></caption>
<graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="fsurg-11-1211325-g006.tif"/>
</fig>
<fig id="F7" position="float"><label>Figure 7</label>
<caption><p>Forest plot of pooled NLR.</p></caption>
<graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="fsurg-11-1211325-g007.tif"/>
</fig>
<fig id="F8" position="float"><label>Figure 8</label>
<caption><p>Forest plot of pooled DOR.</p></caption>
<graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="fsurg-11-1211325-g008.tif"/>
</fig>
<fig id="F9" position="float"><label>Figure 9</label>
<caption><p>SROC curve of included studies. (<bold>A</bold>) Stata 14.0 software for analysis and (<bold>B</bold>) Meta-DiSc 1.4 software for analysis.</p></caption>
<graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="fsurg-11-1211325-g009.tif"/>
</fig>
<p>The PLR value (2.271&#x2009;&#x003C;&#x2009;5) and NLR value (0.713&#x2009;&#x003E;&#x2009;0.2) indicated inferior diagnostic evidence of PCT for ruling in/ruling out diagnoses. The AUC value (0.76&#x2009;&#x003C;&#x2009;0.8) showed a low diagnostic accuracy of PCT, and the low value of DOR indicated that PCT for PJI diagnosis was an inferior target.</p>
<p>Stata 14.0 was selected for sensitivity analysis of the data in this study. The Stata command for sensitivity analysis of this diagnostic meta-analysis was &#x201C;midas tp fp fn tn, modchk (all).&#x201D; One original study (<xref ref-type="bibr" rid="B24">24</xref>) caused the sensitivity of results (<xref ref-type="fig" rid="F10">Figure&#x00A0;10</xref>).</p>
<fig id="F10" position="float"><label>Figure 10</label>
<caption><p>Influence of included studies. (<bold>A</bold>) Goodness-of-Fit. (<bold>B</bold>) Bivariate normality. (<bold>C</bold>) Influence analysis. (<bold>D</bold>) Outlier detection.</p></caption>
<graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="fsurg-11-1211325-g010.tif"/>
</fig>
</sec>
<sec id="s3e"><title>Meta-regression and subgroup analysis</title>
<p>Univariate meta-regression analysis was not conducted because there was no heterogeneity caused by a non-threshold effect in this study. But we performed the following subgroup analysis for variables &#x201C;Study design, Threshold value, MSIS, East Asian race&#x201D; (<xref ref-type="table" rid="T3">Table&#x00A0;3</xref>). The subgroup analysis involves categorizing participants in a study based on certain specific features, which can help researchers explore differences in reactions among different population groups and validate the results of the main analysis.</p>
<table-wrap id="T3" position="float"><label>Table 3</label>
<caption><p>Subgroup analysis of procalcitonin for PJI diagnosis.</p></caption>
<table frame="hsides" rules="groups">
<colgroup>
<col align="left"/>
<col align="center"/>
<col align="center"/>
<col align="center"/>
<col align="center"/>
<col align="center"/>
<col align="center"/>
</colgroup>
<thead>
<tr>
<th valign="top" align="left">Subgroup</th>
<th valign="top" align="center">Number of studies</th>
<th valign="top" align="center">Sensitivity (95&#x0025; CI)</th>
<th valign="top" align="center">Specificity (95&#x0025; CI)</th>
<th valign="top" align="center">PLR (95&#x0025; CI)</th>
<th valign="top" align="center">NLR (95&#x0025; CI)</th>
<th valign="top" align="center">DOR (95&#x0025; CI)</th>
</tr>
</thead>
<tbody>
<tr>
<td valign="top" align="left">Overall studies</td>
<td valign="top" align="center">9</td>
<td valign="top" align="center">0.441 (0.384&#x2013;0.500)</td>
<td valign="top" align="center">0.852 (0.811&#x2013;0.888)</td>
<td valign="top" align="center">2.271 (1.808&#x2013;2.853)</td>
<td valign="top" align="center">0.713 (0.646&#x2013;0.786)</td>
<td valign="top" align="center">5.756 (3.673&#x2013;9.026)</td>
</tr>
<tr>
<td valign="top" align="left" colspan="7">Study design</td>
</tr>
<tr>
<td valign="top" align="left">&#x2003;Retrospective</td>
<td valign="top" align="center">2</td>
<td valign="top" align="center">0.473 (0.367&#x2013;0.580)</td>
<td valign="top" align="center">0.712 (0.579&#x2013;0.822)</td>
<td valign="top" align="center">2.069 (1.369&#x2013;3.126)</td>
<td valign="top" align="center">0.614 (0.477&#x2013;0.792)</td>
<td valign="top" align="center">5.276 (2.25&#x2013;12.367)</td>
</tr>
<tr>
<td valign="top" align="left">&#x2003;Prospective</td>
<td valign="top" align="center">7</td>
<td valign="top" align="center">0.428 (0.360&#x2013;0.498)</td>
<td valign="top" align="center">0.881 (0.838&#x2013;0.915)</td>
<td valign="top" align="center">2.373 (1.805&#x2013;3.120)</td>
<td valign="top" align="center">0.739 (0.665&#x2013;0.820)</td>
<td valign="top" align="center">5.977 (3.494&#x2013;10.224)</td>
</tr>
<tr>
<td valign="top" align="left" colspan="7">Threshold value</td>
</tr>
<tr>
<td valign="top" align="left">&#x2003;0.5&#x2005;ng/ml</td>
<td valign="top" align="center">4</td>
<td valign="top" align="center">0.381 (0.277&#x2013;0.493)</td>
<td valign="top" align="center">0.881 (0.815&#x2013;0.931)</td>
<td valign="top" align="center">3.185 (1.918&#x2013;5.287)</td>
<td valign="top" align="center">0.705 (0.598&#x2013;0.832)</td>
<td valign="top" align="center">6.643 (3.027&#x2013;14.575)</td>
</tr>
<tr>
<td valign="top" align="left">&#x2003;Other</td>
<td valign="top" align="center">5</td>
<td valign="top" align="center">0.465 (0.397&#x2013;0.534)</td>
<td valign="top" align="center">0.834 (0.778&#x2013;0.881)</td>
<td valign="top" align="center">2.015 (1.564&#x2013;2.595)</td>
<td valign="top" align="center">0.717 (0.635&#x2013;0.810)</td>
<td valign="top" align="center">5.345 (3.062&#x2013;9.332)</td>
</tr>
<tr>
<td valign="top" align="left" colspan="7">Diagnostic criteria</td>
</tr>
<tr>
<td valign="top" align="left">&#x2003;MSIS</td>
<td valign="top" align="center">4</td>
<td valign="top" align="center">0.479 (0.407&#x2013;0.552)</td>
<td valign="top" align="center">0.781 (0.709&#x2013;0.843)</td>
<td valign="top" align="center">1.799 (1.390&#x2013;2.328)</td>
<td valign="top" align="center">0.727 (0.637&#x2013;0.829)</td>
<td valign="top" align="center">4.503 (2.505&#x2013;8.093)</td>
</tr>
<tr>
<td valign="top" align="left" colspan="7">Race</td>
</tr>
<tr>
<td valign="top" align="left">&#x2003;East Asian race</td>
<td valign="top" align="center">3</td>
<td valign="top" align="center">0.385 (0.284&#x2013;0.492)</td>
<td valign="top" align="center">0.831 (0.729&#x2013;0.907)</td>
<td valign="top" align="center">3.482 (2.014&#x2013;6.021)</td>
<td valign="top" align="center">0.599 (0.476&#x2013;0.754)</td>
<td valign="top" align="center">8.988 (3.392&#x2013;23.815)</td>
</tr>
</tbody>
</table>
</table-wrap>
<p>In the subgroup of retrospective studies (<xref ref-type="bibr" rid="B23">23</xref>, <xref ref-type="bibr" rid="B25">25</xref>), the pooled SN, SP, PLR, NLR, and DOR were 0.473 (95&#x0025; CI, 0.367&#x2013;0.580), 0.712 (95&#x0025; CI, 0.579&#x2013;0.822), 2.069 (95&#x0025; CI, 1.369&#x2013;3.126), 0.614 (95&#x0025; CI, 0.477&#x2013;0.792), and 5.276 (95&#x0025; CI, 2.25&#x2013;12.367), respectively. In the subgroup of prospective studies (<xref ref-type="bibr" rid="B14">14</xref>, <xref ref-type="bibr" rid="B24">24</xref>, <xref ref-type="bibr" rid="B26">26</xref>&#x2013;<xref ref-type="bibr" rid="B30">30</xref>), the pooled SN, SP, PLR, NLR, and DOR were 0.428 (95&#x0025; CI, 0.360&#x2013;0.498), 0.881 (95&#x0025; CI, 0.838&#x2013;0.915), 2.373 (95&#x0025; CI, 1.805&#x2013;3.120), 0.739 (95&#x0025; CI, 0.665&#x2013;0.820), and 5.977 (95&#x0025; CI, 3.494&#x2013;10.224), respectively. In the subgroup of threshold value with 0.5&#x2005;ng/ml (<xref ref-type="bibr" rid="B14">14</xref>, <xref ref-type="bibr" rid="B24">24</xref>, <xref ref-type="bibr" rid="B26">26</xref>, <xref ref-type="bibr" rid="B29">29</xref>), the pooled SN, SP, PLR, NLR, and DOR were 0.381 (95&#x0025; CI, 0.277&#x2013;0.493), 0.881 (95&#x0025; CI, 0.815&#x2013;0.931), 3.185 (95&#x0025; CI, 1.918&#x2013;5.287), 0.705 (95&#x0025; CI, 0.598&#x2013;0.832), and 6.643 (95&#x0025; CI, 3.027&#x2013;14.575), respectively. In the subgroup of &#x201C;gold standard&#x201D; with MSIS (<xref ref-type="bibr" rid="B23">23</xref>, <xref ref-type="bibr" rid="B25">25</xref>, <xref ref-type="bibr" rid="B27">27</xref>, <xref ref-type="bibr" rid="B28">28</xref>), the pooled SN, SP, PLR, NLR, and DOR were 0.479 (95&#x0025; CI, 0.407&#x2013;0.552), 0.781 (95&#x0025; CI, 0.709&#x2013;0.843), 1.799 (95&#x0025; CI, 1.390&#x2013;2.328), 0.727 (95&#x0025; CI, 0.637&#x2013;0.829), and 4.503 (95&#x0025; CI, 2.505&#x2013;8.093), respectively. In the subgroup of East Asian race (<xref ref-type="bibr" rid="B14">14</xref>, <xref ref-type="bibr" rid="B23">23</xref>, <xref ref-type="bibr" rid="B26">26</xref>), the pooled SN, SP, PLR, NLR, and DOR were 0.385 (95&#x0025; CI, 0.284&#x2013;0.492), 0.831 (95&#x0025; CI, 0.729&#x2013;0.907), 3.482 (95&#x0025; CI, 2.014&#x2013;6.021), 0.599 (95&#x0025; CI, 0.476&#x2013;0.754), and 8.988 (95&#x0025; CI, 3.392&#x2013;23.815), respectively (<xref ref-type="table" rid="T3">Table&#x00A0;3</xref>).</p>
</sec>
</sec>
<sec id="s4" sec-type="discussion"><title>Discussion</title>
<p>Patients suffering from PJI often need long-term antibiotic treatment, secondary revision surgery, joint fusion, and amputation if infection is out of control (<xref ref-type="bibr" rid="B31">31</xref>). Early diagnosis of PJI is essential for orthopedic surgeons. It is possible for doctors to perform debridement, antibiotics, and retention surgery without requiring secondary revision surgery for acute PJI that occurs early after surgery (<xref ref-type="bibr" rid="B32">32</xref>).</p>
<p>It is difficult to diagnose early postoperative infection only relying on serum biomarkers (such as WBC, CRP, and ESR) as they are physiologically increased due to the healing process in the early postoperative stage (<xref ref-type="bibr" rid="B33">33</xref>, <xref ref-type="bibr" rid="B34">34</xref>). ESR and CRP were found to be highly sensitive and lowly specific under all inflammatory conditions (<xref ref-type="bibr" rid="B35">35</xref>, <xref ref-type="bibr" rid="B36">36</xref>). CRP often rised continuously within 30&#x2013;60 days after surgery. ESR and CRP have limitations on the diagnosis of PJI (<xref ref-type="bibr" rid="B11">11</xref>). PCT is one of the most popular indicators in the field of infection diagnosis in recent years. It is composed of 116 amino acids and is produced by Thyroid C cells under physiological conditions. During infection, the body produces a large amount of PCT under the action of various cytokines and bacterial endotoxins. PCT is a peptide hormone of calcitonin precursors or a pro-inflammatory cytokine. Bacterial endotoxins cause elevated levels of PCT in serum. In addition, some non-bacterial infections, such as multiple organ failure and large area burn, can also lead to a significant increase in serum calcitonin (<xref ref-type="bibr" rid="B37">37</xref>). It is suggested in many studies that PCT is a sensitive marker of bacterial infection (<xref ref-type="bibr" rid="B38">38</xref>&#x2013;<xref ref-type="bibr" rid="B40">40</xref>). Therefore, it can be used to accurately distinguish bacterial infection from non-bacterial infections (<xref ref-type="bibr" rid="B41">41</xref>). It is increasingly used to detect and guide the use of antibiotics (<xref ref-type="bibr" rid="B42">42</xref>). It has also become a sensitive and specific marker for the diagnosis of septic arthritis and acute osteomyelitis (<xref ref-type="bibr" rid="B43">43</xref>). Elevated PCT has high specificity for sepsis caused by bacterial infection (<xref ref-type="bibr" rid="B15">15</xref>). It can be used as an indicator for the diagnosis of sepsis, the identification of severe bacterial infection, and the determination of the severity of the disease. In the field of joint replacement, there was no consensus on the value of PCT in diagnosing PJI. PCT was not useful in the diagnosis of local infections such as PJI, but it is important in the diagnosis of sepsis and systemic infection (<xref ref-type="bibr" rid="B44">44</xref>, <xref ref-type="bibr" rid="B45">45</xref>). Bouaicha et al. showed PCT was not the best indicator for the diagnosis of bone and joint infections (<xref ref-type="bibr" rid="B46">46</xref>). Therefore, it could be used as an indicator for inclusion diagnosis instead of exclusion diagnosis because of low sensitivity and high specificity (<xref ref-type="bibr" rid="B46">46</xref>).</p>
<p>Glehr et al. found that the serum PCT (Elecsys BRAHMS PCT) threshold was set at 0.35&#x2005;ng/L with SN (80&#x0025;) and SP (37&#x0025;) (<xref ref-type="bibr" rid="B28">28</xref>), thus currently PCT could be used as an additional test for infection diagnosis. Drago et al. suggested that PCT could not be used as a diagnostic indicator for PJI (<xref ref-type="bibr" rid="B47">47</xref>). Yoon et al. came to the conclusion that PCT with high PLR (12.4) could be used as inclusion criteria for the diagnosis of PJI, but PCT with high NLR (0.44) was not suitable for exclusion of diagnosis (<xref ref-type="bibr" rid="B48">48</xref>).</p>
<p>PJI is primarily an advanced infection, and the incidence of early infection is less than 1&#x0025; (<xref ref-type="bibr" rid="B46">46</xref>). PCT responds directly to bacterial endotoxin, so local joint infection does not cause PCT elevation unless the local infection becomes a systemic infection. PJI is a local low-toxicity infection that cannot produce large amounts of PCT in most cases (<xref ref-type="bibr" rid="B49">49</xref>). This study summarized the results of different studies on the diagnosis of PJI by PCT, which provided a reference for clinical orthopedic surgeons. The results show that the value of serum PCT in the diagnosis of PJI is extremely limited. The pooled SN of PCT is poor, whereas its SP is high. One possible explanation is that PJI is a low-toxin infection that does not have the virulence to trigger PCT release. Second, transient bacteremia is a common phenomenon in healthy patients, even after toothbrushing, which may induce low-level PCT release. In addition, PCT penetration into the synovial fluid has been rarely studied. The extent of PCT penetration into the synovial fluid may vary among patients. Therefore, caution should be exercised when considering PCT in future clinical practice to avoid potentially misleading results (<xref ref-type="bibr" rid="B50">50</xref>). When a patient after THA or TKA has elevated serum PCT, one cannot arbitrarily judge it as PJI and take some radical treatment. While the number of patients in our study may seem limited at 621, it is worth noting that PJI is a rare complication with a low incidence rate. As such, the inclusion of 621 cases in our analysis actually represents a substantial sample size. Moreover, our meta-analysis incorporates data from nine separate studies originating from six distinct countries, rendering our findings remarkably representative. However, there are some limitations in our research. First, there is no gold standard for PJI diagnosis. Second, many studies have shown that the biological biomarker in synovial fluid has a high diagnostic ability for PJI (<xref ref-type="bibr" rid="B51">51</xref>&#x2013;<xref ref-type="bibr" rid="B53">53</xref>). We only studied serum PCT. Third, there were few included cases, and the role of PCT for PJI diagnosis could not be completely reflected. Fourth, in the included literature, some patients with acute infection were clearly excluded, and the other part was not clearly stated. Therefore, we cannot effectively represent the proportion of acute and chronic infections. Fifth, the detection method and time are not similar in all studies, which may have a particular impact on the results.</p>
<p>The PLR value (2.271) and NLR value (0.713) indicate inferior diagnostic evidence of PCT for ruling-in/ruling-out diagnoses. The AUC value (0.76&#x2009;&#x003C;&#x2009;0.80) shows a low diagnostic accuracy of PCT, and the low value of DOR indicates that PCT for PJI diagnosis is an inferior target.</p>
</sec>
<sec id="s5" sec-type="conclusions"><title>Conclusion</title>
<p>This study showed that PCT detection of PJI has poor diagnostic accuracy. PCT is not recommended for use as a rule-out/rule-in diagnostic tool. Consequently, further studies are needed to find markers associated with PCT to improve diagnostic ability. This study examined the current understanding of PCT&#x0027;s diagnostic potential in PJI, providing clinicians with an exclusive reference.</p>
</sec>
</body>
<back>
<sec id="s6" sec-type="author-contributions"><title>Author contributions</title>
<p>Conceptualization: XS and HZ. Literature search: XS, YuL, HZ, YiL, ZL, and YaL. Software: XS, YiL, and YaL. Writing: XS, YuL, YaL, and HZ. All authors contributed to the article and approved the submitted version.</p>
</sec>
<sec id="s7" sec-type="COI-statement"><title>Conflict of interest</title>
<p>The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.</p>
</sec>
<sec id="s8" sec-type="disclaimer"><title>Publisher&#x0027;s note</title>
<p>All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.</p>
</sec>
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