Chest-X-ray-Based Scoring, Total Leukocyte Count, and Neutrophil-to-Lymphocyte Ratio for Prediction of COVID-19 in Patients with Severe Acute Respiratory Illness.

Abstract

This study aimed to use chest-X-ray (CXR)-based scores along with total leukocyte count (TLC) and neutrophil-to-lymphocyte ratio (NLR) in the prediction of coronavirus disease 2019 (COVID-19) in patients presenting with clinical features of severe acute respiratory illness (SARI). This is a retrospective study involving all patients who presented with clinical features of SARI and who had undergone bedside chest X-ray (CXR), hemograms with TLC, NLR, and reverse transcriptase-polymerase chain reaction (RT-PCR) at our institute from May 1 to June 30, 2020. Of 204 patients, 115 tested RT-PCR-positive and 89 tested negative. The patients who presented with SARI, using CXR-based score of 4 or more, TLC of less than 8,700 cells/μL, and NLR of <7 had a statistically significant area under the curve (p<0.001) for diagnosing COVID-19. The sensitivity and specificity of the CXR score was 80.8% and 73.0%, of TLC was 70.1% and 74.7%, and of NLR was 70.1% and 59.0%, respectively, in diagnosing COVID-19 alone. The specificity further increased to 90.4% when we used the CXR score with NLR and to 92.8% when we used the CXR score with TLC. The post-test odds ("rule in" disease) of a positive test for having the disease were 3, 2.77, and 1.71 times with the use of either CXR score, TLC, or NLR criteria, respectively; whereas, combined use of CXR score and NLR increased the post-test odds by 5.53 times, and combination of CXR score with TLC increased the post-test odds by 7.5 times. CXR score with TLC and NLR can predict COVID-19 infection among those who presented with features of SARI. This may help in the early isolation of the patient until the RT-PCR report becomes available.