Clinical Features and Outcomes in Patients with Heparin-Induced Thrombocytopenia (HIT): Report of the CAMC HIT Registry.
Authors: Frame James N. , Davis Elaine , Reed Joan , Wang Ying , Emmett Mary 
Published: October 2019

Abstract
In 2001, our tertiary-care academic medical center implemented a HIT Task Force to develop quality improvement (QI) initiatives for HIT (Blood. 102:2766a, 2003). From these initiatives, a CAMC IRB-approved HIT Registry was developed. We present, from inpatient (IP) Registry data, a retrospective analysis of the clinical features/outcomes of patients (pts) reported/identified with clinical HIT from Jan 1999 to June 2003. IP medical records for case selection were identified from archival pharmacy records, the laboratory records of HIT antibody (Ab) assays, and case-reporting. Demographic features, co-morbid conditions, HIT-cohorts, HIT frequency in open heart surgery (OHS) pts, platelet counts (baseline; time HIT 1st suspected, nadir), thromboembolic complications (TEC), HIT Ab testing (H-PF4 ELISA;HIPA), agents utilized for HIT treatment, mean hospital length of stay (LOS), individual/composite outcomes of new TEC, amputations, and all-cause or HIT-specific mortality are presented. Clinical HIT was identified or recorded in 285 pts: 1999: 35, ‘00: 66, ‘01:63, ‘02:67, 1–6.30.03: 54. The median age was 68 yrs (range, 26–90). M/F (%): 47/53. Co-morbidities included coronary artery disease (68%), hyperlipidemia (49%), diabetes mellitus (40%), renal failure (4.6%), active malignancy (2.5%). The median/mean time from initiating heparin (H) to HIT recognition was 8.7/5.0 days. Median platelet counts (mm3) at baseline/time HIT was 1st suspected/HIT nadir were 208,000/72,000/53,000. A H-PF4 or HIPA assay was (+) in 80% (228). HIT cohorts included OHS (187; 66%), medical admission (69; 24%), & non-cardiac surgery (29; 10%) pts. HIT was identified following IP discharge (D/C) in 19% (35/187) of OHS and 10% (3/29) of non-cardiac surgery pts. The OHS HIT frequency among total OHS pts was: 1.8% (187/10,529). TEC at HIT presentation was 43% (123) and included (> 1 event/pt may have occurred): DVT (101), PE (17), graft occlusion (17), MI (10), venous gangrene (4), TIA (4). A new TEC occurred in 14% (41). Anticoagulant therapy for HIT was administered in 88% of Registry pts: r-hirudin (56%), Argatroban (26%) and danaparoid (6%). The mean duration of direct thrombin inhibitor (DTI) therapy/warfarin overlap with a DTI was 8.9 days /4.5 days. Warfarin was administered at D/C in 78% (176/225) pts. The HIT-admission mean LOS was 21days. The all-cause/HIT-specific mortality was 21% (60)/14% (39). Major bleeding /amputation occurred in 9.0%/2.4%. The composite outcome of new TEC, amputation and all-cause death was 26% (75/285). This report is among the largest reported hospital experiences. HIT was identified most frequently after OHS. Delayed HIT after hospital D/C occurred in 13%. Outcomes comparable to prior reports include time to HIT development, clinical HIT Ab detection, OHS HIT frequency, baseline/new TEC, alternative anticoagulant use, all-cause mortality and the composite outcome. QI initiatives arising from this analysis emphasize initiating DTI therapy when HIT 1st suspected and warfarin when platelets are sufficiently recovered; incorporating a prospective tool for scoring the likelihood of HIT; detailed analyses of the delayed-onset HIT cohort and assessing the financial impact of HIT in hospitalized pts.