Blood Adv. 2021 Sep 20:bloodadvances.2021005314. doi: 10.1182/bloodadvances.2021005314. Online ahead of print.
Heparin thromboprophylaxis is routinely administered during hospitalization for coronavirus disease 2019 (COVID-19). Due to the immune stimulation related to COVID-19, there is ongoing concern regarding a heightened incidence of heparin-induced thrombocytopenia (HIT). We performed a literature search using PubMed, EMBASE, Cochrane and, medRxiv database to identify studies that reported clinical and laboratory characteristics and/or the incidence of HIT in COVID-19 patients. The primary aim was to systematically review the clinical features and outcomes of COVID-19 patients with confirmed HIT. The secondary objective was to perform a meta-analysis to estimate the incidence of HIT in hospitalized COVID-19 patients. A meta-analysis of 7 studies including 5,849 patients revealed the pooled incidence of HIT in COVID-19 of 0.8% (95% confidence interval [CI], 0.2-3.2%; I2 = 89%). The estimated incidences were 1.2% (95%CI, 0.3-3.9%; I2 = 65%) versus 0.1% (95%CI, 0.0-0.4%; I2 = 0%) in therapeutic versus prophylactic heparin subgroups, respectively. The pooled incidences of HIT were higher in critically ill COVID-19 patients (2.2%, 95%CI, 0.6-8.3%; I2 = 72.5%) compared to non-critically ill patients (0.1%, 95%CI, 0.0-0.4%: I2 = 0%). There were 19 cases of confirmed HIT and one with autoimmune HIT for clinical and laboratory characterization. The median time from heparin initiation to HIT diagnosis was 13.5 (interquartile range [IQR], 10.75, 16.25) days. Twelve (63%) developed thromboembolism after heparin therapy. In conclusion, the incidence of HIT in COVID-19 patients was comparable to non-COVID-19 medical patients, with higher incidences with therapeutic anticoagulation and in critically ill patients.