D-dimer as a biomarker for assessment of COVID-19 prognosis: D-dimer levels on admission and its role in predicting disease outcome in hospitalized patients with COVID-19

Introduction Coronavirus Disease 2019 is a primarily respiratory illness that can cause thrombotic disorders. Elevation of D-dimer is a potential biomarker for poor prognosis in COVID-19, though optimal cutoff value for D-dimer to predict mortality has not yet been established. This study aims to assess the accuracy of admission D-dimer in the prognosis of COVID-19 and to establish the optimal cutoff D-dimer value to predict hospital mortality. Methods Clinical and laboratory parameters and outcomes of confirmed COVID-19 cases admitted to four hospitals in Kathmandu were retrospectively analyzed. Admitted COVID-19 cases with recorded D-dimer and definitive outcomes were included consecutively. D-dimer was measured using immunofluorescence assay and reported in Fibrinogen Equivalent Unit (mu g/ml). The receiver operating characteristic curve was used to determine the accuracy of D-dimer in predicting mortality, and to calculate the optimal cutoff value, based on which patients were divided into two groups and predictive value of D-dimer for mortality was measured. Results 182 patients were included in the study out of which 34(18.7%) died during the hospital stay. The mean admission D-dimer among surviving patients was 1.067 mu g/ml (1.705 mu g/ml), whereas that among patients who died was 3.208 mu g/ml (+/- 2.613 mu g/ml). ROC curve for D-dimer and mortality gave an area under the curve of 0.807 (95% CI 0.728-0.886, p<0.001). Optimal cutoff value for D-dimer was 1.5 <mu>g/ml (sensitivity 70.6%, specificity 78.4%). On Cox proportional hazards regression analysis, the unadjusted hazard ratio for high D-dimer was 6.809 (95% CI 3.249-14.268, p<0.001), and 5.862 (95% CI 2.751-12.489, p<0.001) when adjusted for age. Conclusion D-dimer value on admission is an accurate biomarker for predicting mortality in patients with COVID-19. 1.5 mu g/ml is the optimal cutoff value of admission D-dimer for predicting mortality in COVID-19 patients.