Hematological and biochemical markers for predicting severity in COVID-19 patients

The early identification of patients at risk of severe coronavirus disease 2019 (COVID-19) is a clinical priority. This study aimed to evaluate hematological and inflammatory biomarkers between mild and severe cases of COVID-19 in an Indian cohort. A retrospective observational study was conducted on 240 RT-PCR-confirmed COVID-19 patients admitted to Shree Krishna Hospital, Gujarat, India. Patients were classified as severe (n = 170) or non-severe (n = 70) based on clinical criteria. Levels of interleukin-6 (IL-6), ferritin, D-dimer, C-reactive protein (CRP), lactate dehydrogenase (LDH), and hematological parameters were analyzed upon hospital admission. Data were analyzed using SPSS, version 24.0. The Shapiro-Wilk test assessed normality. The Mann-Whitney U test was used for non-normally distributed variables in group comparisons, while the independent samples t-test was used for normally distributed variables. Diagnostic performance was evaluated via Receiver Operating Characteristic (ROC) curve analysis, and associations with severe disease were examined using logistic regression. Patients with severe disease were significantly older (median 61.5 vs. 47 years, p < 0.001). Severe illness was demonstrated significant association with elevated inflammatory markers (IL-6, ferritin, LDH, CRP, D-dimer; all p < 0.001) and hematological dysregulation, notably neutrophilia, lymphocytopenia, and an elevated neutrophil-to-lymphocyte ratio (NLR) (all p < 0.001). ROC analysis identified LDH (AUC = 0.76), ferritin (AUC = 0.74), and NLR (AUC = 0.73) as the best discriminators, with optimal cut-offs of 319 U/L, 255 µg/L, and 4.3, respectively. In multivariate analysis adjusted for age and other biomarkers, only older age (adjusted OR: 1.03 per year; 95% CI: 1.00–1.05; p = 0.008) and elevated ferritin (adjusted OR: 1.44; 95% CI: 1.03–2.01; p = 0.03) maintained a statistically significant independent association with severe disease. The significant univariate associations for IL-6, LDH, and CRP were attenuated in the adjusted model. Admission levels of IL-6, NLR, ferritin, and LDH showed strong associations with COVID-19 severity and offered good discriminatory value for risk stratification. However, after accounting for key confounders, older age and hyperferritinemia were the factors most robustly and independently associated with severe outcomes. These findings underscore the importance of multivariate evaluation to identify core prognostic factors and support the use of accessible biomarkers like ferritin and NLR in triage protocols.