The Role of Platelet-to-Lymphocyte Ratios and Other Markers in Predicting Severity and Prognosis in COVID-19 Patients

Background: Coronavirus disease 2019 (COVID-19) is a respiratory illness with broad spectrum of clinical manifestations ranging from asymptomatic cases to severe complications such as acute respiratory failure, multi-organ dysfunction, and death. Objectives: To evaluate the platelet-lymphocyte ratio (PLR) as a marker of disease severity and mortality in COVID-19 patients. To explore the relationship between PLR and other inflammatory indicators, specifically C-reactive protein (CRP) and neutrophil-lymphocyte ratio (NLR). Methods: The cohort included 400 patients (206 males, 194 females; mean age: 64.5 +/- 17.1 years [range 20-100 years]) who were hospitalized between April 2020 and December 2021. Data were collected on demographic and clinical characteristics, including ward and critical care details. CRP, NLR, and PLR values were recorded on the first and last days of hospitalization. Patients were categorized based on their hospitalization outcomes. Results: PLR statistically increased during hospitalization, from 245 +/- 160 at admission to 341 +/- 747 at discharge (P 0.001). A significant association was found between PLR and both the length of hospital stay and mortality. The mean PLR in the deceased group was 445 +/- 590, compared to 304 +/- 795 in the survivors, P= 0.007. This finding showed a correlation between higher PLR and increased severity and mortality. Conclusions: PLR has been identified as a relevant marker for assessing the severity of COVID-19. Elevated PLR levels are associated with cytokine storm, length of hospital stay, and mortality. The results highlight the relationship between elevated PLR and poor outcome in COVID-19 patients, suggesting its use in monitoring disease progression and prognosis.