Computed tomography severity score and neutrophil-to-lymphocyte ratio: Dual biomarkers for COVID-19 prognostication

BACKGROUND: COVID-19 infection requires an easily accessible yet precise variable for diagnosis and prognosis. This study aims to describe the predictive value of the neutrophil-to-lymphocyte ratio (NL ratio) and computed tomography severity score (CTSS) for COVID-19 diagnosis and deteriorating clinical course, which has yet to be extensively demonstrated. OBJECTIVE: The objective is to determine the correlation between the NL ratio and CTSS and lung injury severity in adult patients with COVID-19 infection. MATERIALS AND METHODS: A retrospective study at a COVID center included 128 hospitalized patients who were COVID-19 positive by reverse transcription polymerase chain reaction or rapid antigen test. The study lasted 6 months (from July 2022 to January 2024). In addition, the patient’s demographics, chest CT findings, C Reactive Protein (CRP), lymphocyte, and neutrophil counts were documented. RESULTS: The differences in NL ratio were significant across all grades of CT severity score groups and within each group ( P < 0.001). There was an excellent correlation between the NL ratio and the CTSS ( r = 0.863, P < 0.001). According to a receiver operating characteristic curve analysis, the NL ratio had diagnostic and prognostic relevance in COVID-19 subjects with negative or positive CT results. The area under the curve was 0.858 (95% confidence interval: 0.728–0.903, P < 0.001), the sensitivity was 69.9%, the specificity was 93.1%, and the optimum NL Ratio cutoff value was 3.734. CONCLUSION: NL ratio is a low-cost predictive tool and a convenient, on-site alternative to a thorax CT scan for determining the degree of lung injury in COVID-19 subjects, particularly in developing countries.