Gastric cancers (GCs) are tumors of the stomach, including non-cardia and subcardia carcinomas (Siewert type III), with the center starting 2–5 cm below the esophagogastric junction (1, 2). GC affected approximately 1,033,701 individuals globally in 2018 (3), and its incidence is highest in Eastern Asia, Eastern Europe, and South America (2, 4). Men are twice as likely to be affected as women (2). The direct cause of GC is unclear, but Helicobacter pylori (Hp) infection and hereditary cancer predisposition syndromes may play a role (5, 6). Patients often present with non-specific symptoms, which may include anorexia, weight loss, abdominal pain, dyspepsia, vomiting, and early satiety (2, 4). In China, the 5-year survival rate of patients with GC is 27.4% (7, 8).

The progression from chronic non-atrophic gastritis, via atrophic gastritis (AG) and intestinal metaplasia (IM), to dysplasia, termed Correa’s cascade (9), is widely considered a common evolution path of the intestinal type of non-cardia GC. AG is the turning point and represents a precancerous lesion. The annual incidence rates of gastric cancer were found to be 0.1, 0.25, 0.6, and 6% in patients with AG, IM, mild-to-moderate dysplasia, and severe dysplasia within 5 years after diagnosis (10). Effective screening and managing of this patient group could reduce the incidence of GC and improve the early detection rate. Gastroscopy followed by pathology is the gold standard for the diagnoses of GC and precancerous lesions, but the large target population of GC endoscopic screening and the lack of high-quality medical resources are major impediments to its implementation (11, 12). In addition, patients with early GC and pre-gastric cancer usually have no specific symptoms (11, 12).

Pepsinogen (PG) is a zymogen abundantly secreted by gastric mucosal cells that is converted into pepsin by the acidic pH in the gastric lumen (13). There are five different groups of PGs, grouped according to their primary structure: PGI, PGII, PGB, prochymosin, and PGF (13). Serum PG amounts can reflect the morphology and function of the gastric mucosa. Indeed, PGI is produced by the adenosine cells of the gastric fundus, and low PGI levels correlate with gastric precancerous lesions and GC (14–16). PGII is more correlated with gastric mucosal lesions compared with those of the gastric antrum mucosa; in addition, PGII is related to gastric duct atrophy, intestinal metaplasia or pseudopyloric gland metaplasia, and dysplasia (17, 18). Interestingly, dysregulated PG expression and a progressive decrease of the PGI/PGII ratio (PGR) are associated with the progression from normal gastric mucosa to precancerous lesions to GC (15, 19). Additionally, PGR plays a critical role in the detection of AG cases (20). Hp has been identified as a carcinogen by the World Health Organization (WHO) (21, 22). The incidence of non-cardiac GC in Hp-positive individuals is 2.97 times that of negative ones (23). A study in Taiwan found that compared with Hp-positive patients, Hp-negative individuals are more likely to develop proximal GC and tend to be younger with more diffuse lesions and worse prognosis (24).

The combination of Hp and PG has been used to evaluate the risk factors for GC, which is probably more suitable for large-scale screening than endoscopy (21). Nevertheless, its efficacy remains unsure, and its cutoff value varies among studies; meanwhile, serum PG levels are affected by race, region, age, gender, height, weight, body surface area, smoking, and alcohol, among others (25). Previous studies showed that serum PG levels and its relationship with GC in China are significantly different from those found in Japan and South Korea (20, 26, 27). There is a high incidence of Hp infection in China, and many studies have shown that PGI and PGII levels increase and PGR decreases after Hp infection. A previous single-center study by our group (20) discussed the classification of PG cutoff values according to Hp infection.

Therefore, the aim of this multicenter cross-sectional study was to examine PG levels and Hp status in asymptomatic individuals undergoing health checkup in order to assess the diagnostic value of serum PG levels for GC and AG.

PGs can be used for GC screening, but the cutoffs vary among studies, and PG levels are influenced by numerous factors. The aim of the present study was to examine the diagnostic value of PG levels and Helicobacter pylori (Hp) status for screening GC and AG in asymptomatic individuals undergoing health checkup in China. This multicenter cross-sectional study suggested that serum PG levels can be used for screening GC and AG. The results suggest that different cutoff values should possibly be used in different Hp status groups and geographical regions, but it will have to be validated in the future using large-sample studies.

AG is an important turning point in the Correa theory (9). Here, in asymptomatic individuals undergoing health checkup, 14.5 and 17.3% participants showed AG and intestinal metaplasia, respectively, while 2.5% had severe AG (OLGA grades III and IV). Such patients have a high risk of developing GC within 5 years. Effective monitoring and intervention in this group are important measures to reduce the incidence of GC and improve the detection rate of early GC. Many factors were independently associated with AG in this work, among which high intake of fruits and vegetables may have a protective effect. Such benefit may be related to vitamin C levels, which are thought to reduce the formation of carcinogenic N-nitroso compounds in the stomach (31, 32). Meanwhile, previous studies have found a strong correlation between citrus fruits and gastric cancer (33). Therefore, the types of vegetables and fruits that could help prevent GC should be assessed in follow-up studies.

A meta-analysis of 31 studies involving a total of 1,520 patients with GC and 2,265 with AG found that serum PG levels have great potential as a non-invasive, population-based screening tool for GC and AG (17). The present study also confirmed that PGI levels and PGRs significantly decreased with the aggravation of atrophy, and PGR was even more significant. Impeding its wide application, PG levels are affected by race, region, age, gender, height, weight, body surface area, smoking, and alcohol consumption, among others (25). The cutoff values of PG for the diagnosis of atrophy vary among studies. Serum PGI ≤70 ng/ml and PGR ≤3 have been the most widely accepted values for detecting AG, with a sensitivity of 66.7–84.6% and a specificity of 73.5–87.1% (34–36). According to a European report, the cutoff values for fundus atrophy are PGI ≤56 ng/ml (sensitivity of 61.9% and specificity of 94.8%) and PGR ≤5 (sensitivity of 75.0% and specificity of 91.0%) (19). A study in Korea suggested that PGI ≤70 ng/ml has a good sensitivity (72.4%) for AG, but a low specificity (20.2%). The sensitivity and specificity of PGR ≤3 were found to be 59.2–61.7% and 61.0%, respectively (18). In the present study, the cutoff values for severe atrophy were significantly different from the above data in the Hp-positive subgroup (PGR ≤9.1 and PGR ≤4.5). In terms of the diagnostic value for GC, the cutoff value was PGR ≤4.7, but in the Hp-negative subgroup, the cutoff was PGR ≤7.1. Still, the number of patients with GC was small in the present study since the study population was made of healthy individuals receiving routine physical examination, and the PG cutoff values for GC were purely exploratory.

Hp infection has a significant effect on serum PG levels. In the present study PGI and PGII levels in the Hp-positive subgroup were higher than those of the Hp-negative subgroup, with PGII being higher and PGR being lower. In addition, Hp infection has been shown to participate significantly in the progression of gastric mucosal inflammation and the development of IM and AG (37, 38). As shown above, Hp prevalence was predominantly elevated in the MAG (49.8%) and SAG (65.3%) groups. China is a country with a high incidence of Hp infection, whose rate in the Chinese population is around 40–55% (20, 39–41). The overall Hp infection rate in the present study was 41.7%, similar to the literature (20). Therefore, using different cutoff values of PG for the Hp-negative and Hp-positive subgroups for detecting GC and AG could be considered, as well as in various regions with distinct Hp infection prevalence rates. Additional studies are required to determine the exact cutoff points of PG in different populations.

In the present study, PG levels in the NAG group showed significant differences among different regions of China. From the perspective of PGR, there were no significant differences between Eastern and Central/Northern China, but these levels were significantly different in Northeast and Southwest China. However, as shown in Table 3 , there were differences in baseline data among regions, especially in Hp infection rate. Thus, differences in PG baseline levels among various regions may be related to these baseline data. Interestingly, there were significant differences in gender, nation, age, diet habit, smoking, and Hp infection rate between Eastern and Central/Northern China, but there was no difference in PGR levels. However, there was a significant difference in PGR levels between Eastern and Southwest China, with no differences in gender, smoking, age, and Hp infection rate, except for diet habit and nation. This suggests that in the subsequent studies assessing PG cutoff in China, it may be necessary to further consider the influence of ethnic groups (Southern China, Northeast China, and Southwest China are the places where ethnic minorities are gathered), dietary habits, Hp infection, and other factors.

This study had limitations. The numbers of patients with lesions and GC were small, requiring further sample size expansion to confirm the above results, especially in asymptomatic individuals. In addition, selection bias might exist since the included patients were individuals intending to undergo gastroscopy, suggesting good socioeconomic status. Large-scale and well-designed prospective studies are warranted for further validation of the cutoff values of PG in different regions in the Hp-negative and Hp-positive subgroups, combining lifestyle indexes such as diet habit and smoking in order to accurately determine the low-risk and high-risk groups for the screening of GC and AG.

In conclusion, dietary habits, smoking, age, and Hp infection are risk factors for GC and AG. Serum PG levels might be used for the screening of AG and GC. The results suggest that different cutoff values should possibly be used in different Hp status groups and geographical regions, but it will have to be validated in future studies with a large sample size. Future studies should also examine the value of PG levels for GC detection.

The datasets presented in this study can be found in online repositories. The names of the repository/repositories and accession number(s) can be found in the article/ Supplementary Material .

The studies involving human participants were reviewed and approved by the ethics committees of various participating hospitals. The patients/participants provided their written informed consent to participate in this study.

YT, YZ, and ZYS carried out the studies, performed the statistical analysis, and drafted the manuscript. HGW, XQH, HWX, HL, PS, LRG, HBW, HZX, YHL, DW, and SZL participated in acquisition, analysis, or interpretation of data. All authors contributed to the article and approved the submitted version.

The work of YT was supported by the National Natural Science Foundation of China (#71804161) and the Zhejiang Province Major Disease Diagnosis and Treatment Technology Research Center (#17-2018-%s-0077). The work of ZS was supported by the China Foundation for Health Promotion (#CHPF-2015-WASC-001).

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.

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