Dosing Patterns and Outcomes in African American, Asian, and Hispanic Patients with Heparin-Induced Thrombocytopenia Treated with Argatroban.

Nonwhites, as compared with whites, have increased risk for thromboembolic complications in heparin-induced thrombocytopenia (HIT) (Lewis et al, Chest 2006). To better characterize the risk in nonwhite patients, we retrospectively evaluated dosing patterns and clinical outcomes in African American, Asian, and Hispanic patients administered argatroban therapy for clinically diagnosed HIT. Patients were from previously reported, multicenter, prospective studies of argatroban therapy (2 mcg/kg/min, adjusted to achieve aPTTs 1.5–3 times baseline) in HIT (defined as an otherwise unexplained platelet count <100 x10⁹/L, or 50% reduction in platelet count, following heparin therapy). For African American (n=52), Asian (n=13), and Hispanic (n=14) patient groups, baseline characteristics, therapeutic argatroban dose and duration, aPTTs during therapy, and clinical outcomes (death, including death due to thrombosis; amputation, including amputation secondary to ischemic complications of HIT; new thrombosis; and major bleeding within a 37-day period) were summarized and compared. Among groups, no differences were detected in demographic or baseline features, excepting weight (median values: 62, 77 and 85 kg, respectively, for Asians, African Americans, and Hispanics). Median baseline platelet counts were 45–71 x10⁹/L, and approximately 50% of patients in each group had HIT-related thrombosis before argatroban was initiated. Each group received a similar duration of argatroban therapy (4.0–5.5 days), yet Asians needed a lesser dose (1.0 mcg/kg/ min, versus 1.9 mcg/kg/min in other groups) to achieve comparable aPTTs (61–69 s). New thrombosis occurred most often in African Americans (21%, versus 7–8% in other groups) and when baseline HIT-related thrombosis was present (9/13 events, 69%). Amputation occurred most often in Hispanics (21%, versus 0–12% in other groups) and when diabetes was present (6/9 events, 67%). Mortality was 21–31%, and mortality due to thrombosis was 0–7%. Asians had the lowest frequency of any thrombotic-related outcome (composite of death due to thrombosis, amputation secondary to ischemic complications of HIT, or new thrombosis: 8%, versus 27–29% in other groups). Two patients, each African American, experienced major bleeding (gastrointestinal), for an overall major bleeding rate of 2.5% and by-group rates of 0–4%. Although limited by small group sizes, our study is among the first to characterize outcomes in minority patients administered nonheparin therapy for HIT. Our findings suggest that, despite achieving comparable levels of anticoagulation with argatroban, African Americans and Hispanics are higher risk patients than Asians for poor outcomes in HIT and also that in minority patients with adverse outcomes, baseline HIT-related thrombosis or diabetes is often present.