Abstract
The severe acute respiratory syndrome corona virus 2 (SARS-CoV-2) is the causative organism of coronavirus disease (COVID)-19 disease. It is associated with systemic inflammatory response characterized by multiorgan involvement. Depending on the extent of involvement of the lungs, the infection can be categorized as mild, moderate, and severe. This retrospective case-control study aimed to assess the severity of COVID-19 infection using hematological parameters like total and differential white blood cell, platelet, and certain derived indices like neutrophil lymphocyte ratio (NLR), monocyte lymphocyte ratio (MLR), platelet lymphocyte ratio (PLR), systemic inflammatory index (SII), and systemic inflammatory response index (SIRI). The study was carried out at the tertiary care teaching hospital in Chennai, India. The study included 455 COVID-19 patients who underwent treatment in the year 2020 (pre-vaccination period), aged more than 18 years, confirmed by reverse transcriptase PCR of nasopharyngeal swabs for SARS-CoV‑2. There were mild (n=320), moderate (n=70), and severe (n=65) COVID-19 cases. Around 270 patients who attended the Department of General Medicine for ailments other than COVID-19 and who were negative for COVID-19 testing were treated as controls. NLR, SII and SIRI were noticeably elevated and were associated with severe form of the disease, reflecting heightened immune activation and dysregulation. Hematological abnormalities of white blood cells and platelets, highlight the impact of cytokine-mediated inflammation. SIRI and SII showed good receiver operating characteristics curve performances. SIRI was associated with other inflammatory variables better than SII. Thus, NLR, SII, and SIRI may serve as reliable, and cost-effective laboratory tests for assessing the severity of COVID-19 infection.
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