D-dimer, clot burden, and outcomes: A retrospective study of ICU patients with COVID-19 pneumonia at a tertiary academic medical center

ABSTRACT

Rationale D-dimer is primarily used in the diagnosis of venous thromboembolic (VTE) disease. Recently the Ddimer test has been used as a marker of inflammation in COVID-19 pneumonia and has been shown to correlate with worse outcomes. An understanding of trajectories and relation to clot burden and outcomes of this novel use of serial measurements of D-dimer in COVID-19 ICU patients remains to be explored. Methods: We reviewed patients who were admitted to the Northwestern Hospital COVID ICUs from 3/1/20 to 7/31/20. We obtained demographics, d-dimer lab values, venous duplex studies from upper and lower extremities (UE/LE dopplers), CT-angiogram (CTA) reports, and mortality outcomes from our electronic medical record database. Reports were processed using string analysis with manual physician validation. Analysis was done in R with nonparametric numeric variables being compared by two-tailed Mann Whitney tests. Results: We had 370 patients in our cohort, with median (interquartile range (IQR)) age being 60 (49-69), 229/370 (62%) male, 128 (35%) of Hispanic ethnicity, 117 (32%) of African-American ethnicity, and 135 (36%) of Caucasian descent. 70 patients died (19%). The total number of VTE imaging tests included 87 CTAs, 102 UE dopplers, and 232 LE dopplers. Clot was discovered in 43/102 (42%) UE dopplers, 62/232 (27%) of LE dopplers, and 25/87 (29%) of CTAs. Patients underwent a median of 2 (1-3) imaging studies, and 10 (4-20) d-dimer measurements. 79 unique patients (21%) had VTE detected. There was no statistically significant difference in age between the clot vs noclot groups 57(45-68) vs 61(49-59) years, p=0.34, or BMI 30.5(25.6-34.8) in clot vs 29(25.4-34.5) kg/m2 in no-clot group (p=0.55). Mortality was significantly higher at 36% in the clot group vs 15% in the group without clot (p<0.005). Hospital length of stay in the group with clot was significantly longer at 30.5(20.3-43.5) days vs no-clot 14(7.9-18.5) days (p<0.0001). The clot group had higher initial d-dimer values 2,236(752-3,654) ng/ml than the no-clot group 757(395-1,940) (p<0.0001), and also higher peak d-dimer values 9,476(3,353-16,595) vs 2,113(686-3,689) ng/ml (p<0.0001). Conclusion: Critically ill COVID-19 patients exhibit a high rate of clot formation. Here we describe a cohort of ICU patients with COVID-19 and their demographics, d-dimer trends, clot burden, and outcomes. Future studies will focus on predictors of clot presence and outcomes based on ddimer trends.