D-dimer as a predictive marker for mortality in hospitalized COVID-19 patients

ABSTRACT

Background: The novel coronavirus disease 2019 (COVID-19) presents an important and urgent threat to global health. Identifying strong predictors of mortality could assist medical staff in treating patients and allocating limited healthcare resources. Aims: The primary aim of this paper was to study the effect of ddimer levels at admission as a predictive marker for in-hospital mortality. Methods: This was a retrospective cohort study evaluating hospitalized patients (age > 18 years), who were positive for COVID-19 based on real-time PCR at one of nine COVID-19 units during the period of the first COVID-19 wave in Lombardy, Italy. The primary endpoint was in-hospital mortality. Information was obtained from patient records. Statistical analyses were performed using a Fine-Gray competing risk survival model. Predictive power was assessed using Harrell's C-index. Results: Out of 1049 patients that were admitted to the emergency department and subsequently hospitalized, 501 patients had evaluable data for d-dimer. Of these 501 patients, 96 did not survive. Cumulative incidence of in-hospital mortality within 30 days was 20%, and the majority of deaths occurred within the first 10 days. (Figure 1) When compared to patients in the lowest quartile of d-dimer blood concentration, the hazard ratio of in-hospital mortality for patients in the 2 nd , 3 rd and 4 th quartile was 3.9 (95CI 1.5-10.0), 5.8 (95CI 2.3-14.7), and 4.6 (95CI 1.8-11.5) respectively, after multivariable adjustment for age, sex and number of comorbidities. The C-statistic of d-dimer for in-hospital mortality was 0.67 (95CI 0.62-0.71). (Table 2) Conclusions: Higher d-dimer levels were strongly associated with inhospital mortality. However, the predictive power of d-dimer alone was not high enough to be useful as a risk prediction score. Future research should focus on the added value of d-dimer as part of a larger risk prediction score.