Comparative Study on the Effect of Vitamin D Deficiency on Platelet Indices in COVID‐19 and Hepatitis C Patients; an Observational Comparative Study

ABSTRACT Background and Aims Despite growing interest in the role of vitamin D in various infectious diseases, limited evidence exists regarding its association with platelet (PLT) parameters in patients with COVID‐19 and Hepatitis C Virus (HCV) infection. This study aims to assess the relationship between serum vitamin D levels and PLT indices in patients with COVID‐19 and chronic HCV. Methods The study included 113 patients with confirmed COVID‐19 and 97 patients with chronic HCV infection. All participants were classified into two subgroups based on their vitamin D status (deficient vs. non‐deficient). The chi‐square test (χ2) or Fisher exact test was used to compare the results between the two groups. Results Patients with COVID‐19 had significantly lower levels of vitamin D compared with HCV patients (p < 0.001). PLT counts were lower in the COVID‐19 group, and MPV, PDW, and inflammatory markers (PLR, MPR, and MLR) were significantly higher. Also, a significant negative correlation was observed between vitamin D levels and MPV in both groups (p < 0.001). In patients with vitamin D deficiency, PLT and inflammatory changes were more pronounced in COVID‐19 than in HCV. Conclusion The results of this study showed that COVID‐19 patients had lower vitamin D levels, lower PLT counts, and higher indices of platelet activation compared with HCV patients. These changes are associated with the severity of the inflammatory response in COVID‐19 and could be part of the mechanisms that cause thrombotic complications in this disease.