Predictive role of neutrophil-to-lymphocyte ratio (NLR) in the progression of COVID-19 patients in intensive care unit

Aims: The aim of this study was to evaluate the neutrophil-to-lymphocyte ratio (NLR) as a predictive marker for the prognosis of COVID-19 patients, in order to provide an easy, accessible, and cost-effective way to measure inflammation. Methods: A total of 365 patients, aged over 18 years and admitted to the intensive care unit (ICU) between 01.08.2020 and 31.03.2021 with a positive RT-PCR test for COVID-19, were included. This was a single-center, retrospective study. Demographic data and laboratory results of the patients at the time of the first admission and ICU admission were analyzed. The relationship between NLR values at initial presentation and ICU admission with patient prognosis was statistically investigated. Results: In our study, we found that NLR and d-NLR values at the time of initial hospital admission and ICU admission had a predictive role in forecasting 30-day mortality in COVID-19 patients admitted to the ICU. An NLR cutoff value of>0.48 at first presentation predicted mortality with a sensitivity of 72.2% and a specificity of 46.0%. An NLR cutoff value of 11.7 at ICU admission predicted mortality with a sensitivity of 64.7% and a specificity of 60.9%. Additionally, procalcitonin, CRP, IL-6, D-Dimer, and ferritin levels at both initial admission and ICU admission were found to have a predictive role in mortality. Conclusion: The NLR is a predictive marker for mortality in ICU patients. The lower sensitivity and specificity values compared to those in the literature are attributed to differences in the age, comorbidities, and clinical severity of the patient population included in this study.