Utility of Neutrophil-Lymphocyte Ratio (NLR) as an Indicator of Disease Severity and Prognostic Marker among Patients with Covid-19 Infection in a Tertiary Care Centre in Bangalore – A Retrospective Study

Abstract

BACKGROUND The infection caused due to novel coronavirus 2 can cause wide spectrum of disease from asymptomatic mild disease to life threatening disease. The widespread inflammation is most likely the cause of the adverse outcomes. There are numerous markers of the inflammation which are used to identify the severity and prognosis of the disease. Neutrophil lymphocyte ratio (NLR) is one such marker which is easily available and feasible in all the hospital settings. This study intended to evaluate the NLR as a marker of disease severity and prognosis, in those with Covid-19. METHODS This was a retrospective study to determine the utility of NLR as a marker of severity and prognosis among patients with Covid disease. Medical records of 60 patients admitted with mild to moderate Covid-19 disease were reviewed and relevant data was retrieved. The NLR at admission and 72 hours later was noted. High resolution computerised tomography was done and computerised tomography severity score (CT-SS) was calculated. The outcomes of these patients were noted. RESULTS Mean NLR at admission in mild disease was 5.6 and in moderate disease was 9.2. This difference was found to be statistically significant. It was also seen that NLR had a positive co-relation with CT severity score, duration of hospital stay, Creactive protein (CRP) and D-dimer. For predicting mortality, NLR with cut off of 6.6 had a sensitivity of 100 % and a specificity of 66.07 %. CRP with cut off of 6.8 had sensitivity of 100 %, specificity of 76.79 %. D-dimer with cut off of 1.6 had specificity of 78.58 %. For predicting severity, NLR with cut off of 6.6 had sensitivity of 75 % and specificity of 80 %. CRP with cut off of 7.9 had sensitivity of 65 % and specificity of 100 %. D-dimer with cut off of 1.3, had sensitivity of 90 % and specificity of 97.5 %. CONCLUSIONS The study shows that neutrophil–lymphocyte ratio is a good indicator of disease severity and has prognostic significance in Covid-19. There is a positive correlation with high-resolution computed tomography (HRCT) chest score and other markers of inflammation among patients with Covid-19. Serial monitoring of NLR can be utilised as a surrogate to HRCT chest to determine disease severity whenever the latter is not available. This can ensure early intervention and help prevent mortality. KEYWORDS Neutrophil-Lymphocyte Ratio, Severity of Covid