Neutrophil-Lymphocyte Ratio and Platelet-Lymphocyte Ratio for an Early Detection of Venous Thromboembolism in COVID-19 Patients

Abstract

Background: Venous Thromboembolism (VTE) is an umbrella term that includes both deep vein thrombosis (DVT) and pulmonary embolism (PE). COVID-19 infection has emerged as a risk factor for VTE; however, traditional methods of testing (D-dimer and Well's score) have been less than optimal. The neutrophil to lymphocyte ratio (NLR) and platelet to lymphocyte Ratio (PLR) have a role in diagnosing DVT in non-COVID19 patients. These two inexpensive values are readily available from the complete blood count (CBC). Objective: To determine the association of NLR and PLR on admission and imaging day with the incidence of VTE in COVID-19 patients. Methods: This was a historical cohort study of all patients admitted with COVID-19 from 2020-2021, who underwent duplex ultrasound (US) and/or computed tomography angiography (CTA) of the chest, and serial complete blood counts (CBC) with differential measurements during hospitalization. Patients who had risk factors for VTE (active malignancy, history of thrombophilia disorders and any anticoagulation therapy) were excluded. The NLR and PLR were calculated on admission and upon imaging for eligible patients. Data were analyzed using Student's t-test, analysis of variance, the x2 test and logistic regression. Results: We included 234 patients, 51.3% (120/234) female, 57.3% Black (134/234) with mean age 59.2 ± 15.9 years. The mean NLR on admission for all admitted patients was higher in the VTE group vs non-VTE group, 11.24 ±11.33 vs 7.66 ±5.16 respectively, (p=0.002). The mean NLR on admission for non-ICU patients was higher in the VTE group vs non-VTE group, 9.06 ± 5.72 vs 7.04 ± 4.53 respectively, (p=0.02). For ICU patients, the mean NLR on admission was higher in the VTE group vs non-VTE group, 14.49 ±16.01 vs 8.6±4.53 respectively, (p=0.02).. There was no association between PLR on admission, NLR and PLR on imaging and incidence of VTE. After controlling for sex, every unit increase in NLR at admission increased the risk of VTE by 6.8% (OR=1.068, p=0.005). Conclusion: NLR on admission may be a useful, readily available and inexpensive method of screening for VTE in patients with COVID-19 infection.