Evaluating The Utility of Interleukin-6, C -Reactive Protein (CRP) and Procalcitonin in Predicting Disease Severity and Prognosis in Hospitalized SARS-CoV-2 Patients: A North Indian Retrospective Study

Background: Coronavirus disease 2019 (COVID-19) associated inflammatory cytokine storm that worsens COVID-19, relies heavily on the inflammatory response. IL-6, a TH1 cytokine, PCT and CRP have been linked to serious illness and a higher mortality rate. We further tried to evaluate the role of these indicators and their association with clinical severity in COVID-19 patients. Material and Methods: Eighty-three consecutive patients with age ≥18 years with RT-PCR test positive for SARS-CoV-2 were included in the study. Demographic characteristics (age and sex), underlying co-morbidities, symptoms, physical findings, and laboratory tests of the patients were recorded. All patients were categorized as having mild, moderate, and severe COVID-19 disease, according to the Indian Council of Medical Research (ICMR). The levels of IL-6 and PCT were estimated by electrochemiluminescence immunoassay (ECLIA) using Cobas-e411 Immunoassay System, and Quantitative CRP was done by Unicorn-230 automated biochemistry analyzer to find out their correlation with disease severity and outcome. Multiple Regression was performed to find out factors associated with the adverse outcome of the disease. Result: Mean age of patients was 51 years. IL-6, CRP, and PCT levels increased in 73 %, 68.0 %, and 8.2 % patients on admission, respectively. The most common co-morbidity associated with the disease was hypertension (25%), followed by diabetes (24%) and respiratory disease (15%). Increased IL-6, CRP, and PCT levels were found in 77 percent, 79 percent, and 20 percent of patients, respectively. We found that IL-6 (P≤0.05), CRP (P≤0.05), and PCT (P≤0.05) were significantly raised in COVID-19 patients with increasing severity of the disease. The Area under the receiver operating characteristic (AUROC) of these parameters ranged between 0.65 and 0.8 (IL-6, 0.828; CRP, 0.809; and PCT, 0.658), indicating a reliable biomarker to assess clinical severity. Conclusion: Sequential measurement of blood levels of IL-6, CRP, and PCT levels is useful in determining the severity and predicting the outcome of the patients with severe disease. IL-6 and CRP have an independent prognostic value. On the other hand, the importance of normal PCT concentrations in patients with viral pneumonia needs to be studied further.