The role of C-reactive protein, procalcitonin, interleukin-6 and neutrophil / lymphocyte ratio as a laboratory biomarker in COVID-19

The Egyptian Journal of Immunology
Volume 31 (2), April, 2024
Pages: 93 – 101.
Rusul S. F. Al-Juboori1, and Yasmeen J. Al-Bayaa2
1Ibn Sina University of Medical & Pharmaceutical Sciences, Baghdad, Iraq.

2College of Medicine, University of Baghdad, Baghdad, Iraq.

Corresponding author:
Yasmeen J. Al-Bayaa, College of Medicine, University of Baghdad, Baghdad, Iraq.


Biomarkers such as Interleukin-6 (IL-6), Procalcitonin (PCT), C-reactive protein (CRP) and Neutrophil-Lymphocyte Ratio (NLR) have a role in the pathogenesis of severe coronavirus disease 2019 (COVID-19). The aim of this study was to explore the differences between serum levels of such biomarkers in severe and non-severe COVID-19 cases and compare them with normal people and to evaluate the sociodemographic variables and chronic diseases effect on the severity of COVID-19. The study included 160 subjects, divided into two groups, a case group of 80 patients, and a control group of 80 normal persons. The case group was divided into two subgroups: 40 severe COVID-19 patients and 40 patients with non-severe disease. Blood IL-6 was assessed by an enzyme-linked immunosorbent assay (ELISA), PCT by an immunoassay, CRP by an immunoturbidimetric assay and NLR from CBC. The levels of IL-6, PCT, CRP, and NLR were significantly higher in the case group than in control group (p= 0.001, for all). However, there was no difference between these biomarkers level in the non-severe COVID-19 subgroup and the control group (p>0.05 for all). The proportion of severe COVID-19 was significantly higher in patients aged >50 years, and in patients with chronic diseases (p=0.046 and p=0.001, respectively). We also found a strong correlation between such biomarkers and old age, and chronic diseases with the disease severity. There was a significant difference in the level of the three biomarkers (IL-6, PCT, CRP, and NLR) between patients’ subgroups and the control group. In conclusion, since the levels of these biomarkers are correlated with the severity of the COVID-19 disease, and there was a difference in the levels between the groups with severe and non-severe symptoms, we suggest a role of these biomarkers in predicting the severity COVID-19 disease and its poor prognosis.

CRP, Procalcitonin, IL-6, Neutrophil/Lymphocyte Ratio, COVID-19.

Date received:
23 November 2023; accepted: 15 March 2024



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