Exploring heterogeneity in reported venous thromboembolism risk in COVID-19 and comparison to other viral pneumonias: a systematic review and meta-regression

Abstract

BackgroundSources of heterogeneity in venous thromboembolism (VTE) risk in COVID-19 are unclear and comparisons to other viruses are lacking. ObjectivesTo describe VTE risk in patients with COVID-19, explore sources of heterogeneity, and make comparisons with other viral pneumonia. MethodsPubMed and Embase data were searched on March 14, 2021, for studies on VTE in adults hospitalized with viral pneumonia. VTE risk estimates were pooled in a random effects meta-analysis stratified by virus type. Heterogeneity in COVID-19 was explored in multivariable meta-regression. ResultsSeventy studies in COVID-19 (intensive care [ICU] [47] vs ward [23]), 4 studies in seasonal influenza (ICU [3] vs ward [1]), 2 ICU studies in H1N1 and 1 ICU study in SARS-CoV-1 were included. For COVID-19 ICU, pooled VTE risk was 19.6% (95% confidence interval [CI], 16.2%–23.5; I2 = 92.8%) for nonscreening studies and 30.0% (95% CI, 17.9%–45.7%; I2 = 81.9%) for screening studies. For COVID-19 ward, pooled VTE risk was 3.4% (95% CI, 2.4%–4.7%; I2 = 91.3%) and 22.5% (95% CI, 10.2%–42.7%; I2 = 91.6%) for nonscreening and screening studies, respectively. Higher sample size was associated with lower VTE risk. Pooled VTE risk in seasonal influenza and H1N1 at ICU were 9.0% (95% CI, 5.6%–14.2%; I2 = 39.7%) and 29.2% (95% CI, 8.7%–64.2%; I2 = 77.9%), respectively. At ward, VTE risk of seasonal influenza was 2.4% (95% CI, 2.1%–2.7%). In SARS-CoV-1, VTE risk was 47.8% (95% CI, 34.0–62.0). ConclusionPooled risk estimates in COVID-19 should be interpreted cautiously as a high degree of heterogeneity is present, which hinders comparison to other viral pneumonia. The association of VTE risk in COVID-19 to sample size suggests publication bias.