The Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) pandemic has devastated humanity since its outbreak in 2019 (Chekol Abebe et al., 2022). Great efforts have been made to describe its pathophysiology and develop more effective treatments (Wang and Yang, 2023; Yang and Wang, 2023) In addition to the lungs, the virus has been proven to damage several other systems, including the heart, gastrointestinal tract, neurological system, kidney, coagulation, and endothelium (Iba et al., 2020; Puelles et al., 2020). However, a number of hematological parameters, such as lymphopenia and increased D-dimers, have been observed in COVID-19 patients (Rahi et al., 2021). Several studies have consistently indicated that higher red blood cell distribution width predicts worse outcomes in individuals with COVID-19 infection. However, anemia has been reported to be an independent predictor of disease severity in COVID-19 infection (Bellmann-Weiler et al., 2020; Higgins et al., 2020; Banon et al., 2021).

Red blood cells (RBC) are the carriers of oxygen throughout the body and are known to lyse in cases of infection (Bouchla et al., 2022), especially with the increasing complications of sepsis (Bateman et al., 2017). Previous studies have shown that the virus can invade erythrocytes by interacting its S1 spike protein with erythrocyte CD147 (Al-Salih et al., 2020) and the band-3 protein (Cosic et al., 2020). However, viral spike proteins and complement activation products have been detected on the cell surface of erythrocytes from patients with COVID-19. Therefore, it is thought to affect erythrocyte rheology, leading to intravascular thrombosis and associated lung injury (Lam et al., 2021).

Additionally, the hypercoagulation and inflammatory state lead to more fragility and make elastic the membrane of RBC (Grobler et al., 2020). It has been demonstrated that high serum ferritin levels in COVID-19 patients might result in hyper-activated interactions between erythrocytes and platelets (Youssry et al., 2022), indicating a connection between erythrocyte alterations and thrombosis in COVID-19 disease (Venter et al., 2020).

The understanding about the immune response of SARS-CoV-2 has been studied in detail in different cohort studies. Moreover, due to the significant sequence homology throughout the coronavirus family, several scientists have hypothesized the interaction between SARS-CoV-2 and the host organism may be related to another coronavirus (Vabret et al., 2020). Previously, the immunological dysfunction caused by SARS-CoV-2 confirmed the activation of innate and adaptive immune responses (Yang et al., 2004; Chu et al., 2016). Therefore, viral infection may have damaged the immune system and may be reflected as a change in peripheral blood cells.

Lymphocytes are essential for maintaining immunological homeostasis during infection (Channappanavar et al., 2014). Several studies have shown that lymphopenia can predict longevity in COVID-19 patients (Yang et al., 2004; Channappanavar et al., 2014) Additionally, numerous investigations have revealed that eosinophilia is associated with poor prognosis. (Cortés-Vieyra et al., 2021; Singh et al., 2022). Thus, immunological damage at an early stage of the disease may be indicated by the differentiation of peripheral leukocytes. However, modulation in the levels of eosinophils are the risk factors for changes in peripheral blood cells (Tong et al., 2021).

This study aimed to analyze the effect of COVID-19 on serum and hematological parameters in, DM, HTN, and different cardiovascular diseases before a detailed investigation as a rapid diagnostic tool to reduce the risk of mortality in respective patients.

Data was collected from 1,113 hospitalized patients, including 495 males and 618 females, in the intensive care unit of Qazi Hussain Ahmad Teaching Hospital, Nowshehra, Pakistan, due to severe COVID-19 disease with SpO₂ levels less than 75 mmHg, from April 2020 to January 2023. In addition, earliest clinical manifestations such as fever, cough, dyspnea, muscle pain, diarrhea fatigue, and loss of smell and taste recorded in medical history taken upon admission. Furthermore, in the present research work only those patients and normal individuals were considered who were not previously vaccinated. Herein, two control groups were used to better understand the results and their blood was collected from respective departments. Control group 1 was composed of 502 male and female patients with DM, HTN, IHD and MI without COVID-19. However, in control group 2, 660 normal individuals, including 305 males and 355 females, were included without DM, HTN, IHD, MI and COVID-19. Furthermore, patients with renal diseases, hepatic dysfunction, anemia, myeloid tumor, or other diseases were excluded. Whole blood and serum samples were obtained from all participants in EDTA and serum tubes under the supervision of expert and qualified medical physician and standard operating procedures in the hospital. Laboratory investigations, chest CT imaging, and SpO₂ levels were performed immediately after the hospitalization of patients. The present study was approved by the ethical committee of Kohat University of Science and Technology, Kohat, Pakistan under Reference No: Ref-No/KUST/Ethical Committee/528. In this study, written informed consent was obtained from all participants. The study was conducted following the guidelines of the Declaration of Helsinki (World Medical Association declaration of Helsinki, 2013: Ethical principles for medical research involving human subjects, 2013).

In this study, hospitalized SARS-CoV-2 patients with different diseases, including COVID-19 only, DM, HTN, and other cardiovascular diseases, were included. In addition, an age and gender-matched healthy control group for each disease group was also included. The demographic characteristics showed that the ratio of COVID-19 was high in female patients of COVID-19 only, DM, MI, MI with HTN, MI with DM, and MI with DM and HTN patients. In addition, the ratio of COVID-19 was high in male patients in the HTN, IHD, IHD with DM, and DM with HTN groups given in Figure 1.

SARS-CoV-2 can affect various physiological systems, including the blood and immune system. The SARS-CoV-2 primarily targets the respiratory system (Rahi et al., 2021). However, the infection can have systemic effects. The impact on serum and hematological parameters can vary among individuals and is influenced by factors such as age, overall health, and the severity of the infection (Bellmann-Weiler et al., 2020; Higgins et al., 2020). This statement agrees with our results, which demonstrate that SARS-CoV-2 infection significantly modulates serum and hematological parameters in the existing health condition.

The elevated levels of liver enzymes are frequently observed by different physicians during their clinical practice. Therefore, it can be difficult to evaluate such problems in people with no symptoms. In addition, liver enzymes are also elevated during different hepatitis infections, fatty liver disease, obesity and hemochromatosis, etc (Malakouti et al., 2017). Kidney failure may also occur during chronic DM and may elevate the levels of urea and creatinine in blood (Dabla, 2010). Furthermore, high levels of urea and creatinine are also found during glomerulonephritis, use of certain drugs and consuming large amounts of protein diets, etc. It indicates that it may be difficult to identify the cause of elevated levels of liver enzymes, urea and creatinine. Therefore, in the present cohort study we selected precise markers that modulate during SARS-CoV-2 infection. The abnormal coagulation during COVID-19 results in the elevated level of D-dimer (Han et al., 2020). The clinical investigations to diagnose the deep vein thrombosis or pulmonary embolism suggested that the elevated level of D-dimer directly linked with the risk of irregular blood clotting (Querol-Ribelles et al., 2004; Yao et al., 2020). However, several studies depicted 3 to 4-folds increase in D-dimer levels to be associated with the better prognosis in COVID-19 patients. However, in the present study elevated D-dimer levels have also been identified in solo and multiple disease conditions of DM, HTN, IHD and MI infected with COVID-19. Therefore, the early stages of the disease’s coagulation parameters can also help to prevent and treat COVID-19 infection. The detailed investigation of serum ferritin as a marker of iron metabolism demonstrated that the changes in its concentrations is one of the systemic symptoms of the acute phase reaction (de Lucena et al., 2020). Serum ferritin has been investigated for a long time as a marker of iron metabolism (Wang et al., 2010; Henry et al., 2020b; Vargas-Vargas and Cortés-Rojo, 2020). Moreover, it has been demonstrated that the high ferritin levels result due to acute inflammatory reactions. Likewise in the current investigation, the recorded serum ferritin level was significantly increased both in solo as well as multiple disease conditions of the patients infected with COVID-19. CRP level is the key indicator associated with the degree of inflammation irrespective of the age and gender (Bilgir et al., 2015). The high CRP levels can be utilized to the early diagnosis of the severe lung infections in the patients with severe pneumonia (Warusevitane et al., 2016). In the present study, the significantly increased levels of inflammatory marker such as hs-CRP were observed in all the disease conditions of COVID-19 infection that can also be used as rapid diagnostic markers for disease severity at early stages of infection. The inflammatory responses showed the association between infectious cells, the immune system, and the inflammatory response, mimicking nonspecific responses to hypoxia, tissue injury, and necrosis. Moreover, previous studies also explored that several conditions such as cancer, heart failure, hypothyroidism, and viral diseases, including COVID-19, can increase LDH levels (Henry et al., 2020a; Wu et al., 2020). In the present cohort, the LDH level was significantly increased in patients of solo and multiple disease conditions of DM, HTN, IHD and MI infected with COVID-19.

Previous studies showed that specific laboratory parameters at the time of hospitalization were linked to mortality and the severity of the COVID-19 infection (Allouche et al., 2021; Anai et al., 2021; Al-Saadi and Abdulnabi, 2022; Gajendra, 2022). However, the present findings showed a low level of Hb in COVID-19 patients at the time of admission to the ICU and were associated with disease severity (Freeman and Morando, 2018). Therefore, a decline in Hb level upon diagnosis of COVID-19 may be a sign of acute respiratory failure. Moreover, the low level of Hb was also observed in all the patients infected with COVID-19 and hence could be assigned to acute respiratory failure in COVID-19 infection. The state of leukocytosis could be substantially associated to the death of individual which can be occurred in response to the external stimuli including infection, inflammation, drugs, malignancies, poisoning and ketoacidosis. Furthermore, it is also associated with acute leukemias, chronic leukemias and myeloproliferative disorders (Asadollahi et al., 2011). Therefore, in COVID-19 infection, a higher TLC count should receive more significant consideration, which would help practitioners to take an even more effective treatment (Zhu et al., 2021). However, in the present study, elevated levels of TLC were observed in all the patients with different disease conditions infected with SARS-CoV-2. In addition, during the onset of COVID-19 infection, viral spike proteins and complement activation products have been detected on the cell surface of erythrocytes and reduce the level of RBC. However, the RBC levels were not significantly reduced in the present investigation. In the severe stage of SARS-CoV-2 infection, the increase risk of mortality is also associated with thrombocytopenia. The first cellular response to vascular injuries and thrombosis is the elevation in the levels of platelets. Hence by releasing numerous potent cytokines and chemokines, the platelets can link the immune system to thrombotic events (Franco et al., 2015). In the present finding, thrombocytopenia has been observed in all the patients infected with COVID-19. The findings of the current investigation observed thrombocytopenia in all the studied patients infected with SARS-CoV-2. Moreover, the present findings also showed significant differences for some parameters including Hb, TLC, RBC, and platelets as compared to control, although the index was in the normal range.

Hemophagocytic lymphohistiocytosis disorder is considerable associated with the several species of viral infections (Mostaza-Fernández et al., 2014). However, differentiation in the peripheral white blood cell composition could indicate immunologic dysfunction during COVID-19 infection (Higgins et al., 2020). Likewise, neutrophilia is another sign of cytokine storm and hyper-inflammation state and hence considered as a predictor of disease severity in COVID-19 infection. (Chan et al., 2021). Therefore, neutrophilia is also considered a predictor of disease severity in COVID-19 infection. On the other side, as a poor prognostic indicator several studies also demonstrated the association of eosinophilia with COVID-19 disease severity. Severe SARS-CoV-2 patients have lower lymphocyte counts and higher leukocyte counts, identified as a prognostic indicator (Tong et al., 2021). However, elevated levels of neutrophil-to-lymphocyte ratio (NLR) and neutrophil-to-monocyte (NMR) ratio have emerged as independent hallmarks of severe COVID-19 infection (Rizo-Téllez et al., 2020; Reusch et al., 2021). In the present cohort, lymphopenia, monocytopenia, neutrophilia, eosinopenia, and basopenia have been observed in all the patients with solo and multiple disease conditions of DM, HTN, IHD and MI. In addition, high NLR and NMR were also observed in all the respective disease conditions infected with Severe SARS-CoV-2.

This study provides evidence of a relationship between COVID-19 infection and modulation in serum and hematological parameters. However, severe SARS-CoV-2 infection induces changes in the serum and hematological parameters which could be used as a marker for the rapid diagnosis of SARS-CoV-2 infection in patients with solo and multiple disease conditions of DM, HTN, IHD and MI.