Utility of Biochemical Markers in Predicting Severe COVID-19: Experience from a Tertiary Hospital in South India.

Background: Coronavirus Disease 2019 (COVID-19) patients can present with a wide array of symptoms. For laboratory investigation of these patients several biochemical tests are routinely requested. Here we wanted to evaluate the utility of procalcitonin (PCT), ferritin, D-dimer, interleukin 6 (IL-6) and total lactate dehydrogenase (LDH) activity in predicting severe COVID-19 infection. Patients and methods: This study was undertaken at a tertiary care medical hospital in Tamil Nadu, India representing 183 COVID-19 RT-PCR positive patients, who were grouped based on their disease severity as mild (n=21), moderate (n=115) and severe (n=47) cohorts. All routine clinical chemistry analysis was performed as part of routine baseline assessment. Biomarkers of inflammation and infection were tested via the measurement of IL-6, PCT, ferritin, and D-dimer. Serum IL-6 concentration was estimated by ELISA, while total LDH activity was analyzed by kinetic colorimetric assay. Serum ferritin, PCT and D-dimer were measured by fluorescent immunoassay by sandwich immuno-detection method. Results: Biomarkers were significantly different among subgroups, and the highest concentrations were found in those with intensive care unit (ICU) admission. Serum PCT showed the best power to predict the need for ICU treatment followed by D-dimer, IL-6 and total LDH. Based on the AUC-ROC analysis, mortality was most effectively indicated by D-dimer followed by PCT, LDH, IL-6 and ferritin. Conclusion: Our study highlights the utility of some routinely available biochemical tests in the management of severe COVID-19. The higher baseline values of these biomarkers hint towards the probability of severe infection and a larger risk of death.