Relationship between leukocyte, neutrophil, lymphocyte, platelet counts, and neutrophil to lymphocyte ratio and polymerase chain reaction positivity

Background: Exposure to viral or bacterial pathogens increases the number of neutrophils with a relative decrease in lymphocytes, leading to elevated neutrophil to lymphocyte ratio (NLR). This study aimed to investigate whether differences in NLR among real-time polymerase chain reaction (PCR)-positive and-negative patients presenting with a prediagnosis of COVID-19 pneumonia could be useful in the differential diagnosis. Methods: The study included 174 patients admitted because of suspected COVID-19 infection between March and April 2020. Patients were divided into two groups: PCR-negative and PCR-positive. Hemogram, NLR, urea, creatinine, aspartate aminotransferase, alanine aminotransferase, bilirubin, ferritin, D-dimer, C-reactive protein, procalcitonin, troponin, and coagulation parameters were analyzed. Results: On comparison of laboratory parameters between both groups at presentation, PCR-positive patients were significantly more likely to have leukopenia (p < 0.001), thrombocytopenia (p = 0.006), neutropenia (p < 0.001), lymphopenia (p = 0.001), and increased NLR (p = 0.003). Furthermore, PCR-positive patients showed significant elevations of ferritin (p = 0.012) and procalcitonin (p = 0.038) and significant lower potassium levels (p = 0.05). Conclusion: COVID-19 pneumonia has become a major global health problem. Early diagnosis and treatment of these patients are crucial, as COVID-19 pneumonia shows a rapid progression in most cases. Thus, leukopenia, thrombocytopenia, elevated NLR, and elevated ferritin may be useful as supplementary diagnostic tests in these patients, which may allow early initiation of treatment and may contribute to preventing progression in patients with abnormal results.