In this paper, recently published in Arteriosclerosis, Thrombosis, and Vascular Biology, the authors aimed to determine the prevalence of D-dimer elevation in COVID-19 hospitalisation, trajectory of D-dimer levels during hospitalisation, and association with clinical outcomes. Consecutive adults admitted to a large New York City hospital system with a positive PCR test for SARS-CoV-2 between March 1, 2020 and April 8, 2020 were identified. Outcomes included critical illness (intensive care, mechanical ventilation, discharge to hospice, or death), thrombotic events, acute kidney injury, and death during admission. Among 2377 adults hospitalised with COVID-19 and ≥1 D-dimer measurement, 1823 (76%) had elevated D-dimer at presentation. Patients with elevated presenting baseline D-dimer were more likely than those with normal D-dimer to have critical illness (43.9% versus 18.5%; adjusted odds ratio, 2.4 [95% CI, 1.9–3.1]; P<0.001), any thrombotic event (19.4% versus 10.2%; adjusted odds ratio, 1.9 [95% CI, 1.4–2.6]; P<0.001), acute kidney injury (42.4% versus 19.0%; adjusted odds ratio, 2.4 [95% CI, 1.9–3.1]; P<0.001), and death (29.9% versus 10.8%; adjusted odds ratio, 2.1 [95% CI, 1.6–2.9]; P<0.001). Rates of adverse events increased with the magnitude of D-dimer elevation; individuals presenting with D-dimer >2000 ng/mL had the highest risk of critical illness (66%), thrombotic event (37.8%), acute kidney injury (58.3%), and death (47%). The authors concluded that abnormal D-dimer was frequently observed at admission with COVID-19 and was associated with higher incidence of critical illness, thrombotic events, acute kidney injury, and death.