Characteristics and outcomes of 16 Hamilton patients with HIT treated with rivaroxaban
| Patient age (years) . | Sex . | 4Ts score (points) . | EIA-IgG (OD units) . | Serotonin-release assay peak % release . | Patient clinical setting . | HIT-associated thrombosis . | Platelet count at rivaroxaban start . | Anticoagulant before rivaroxaban . | Rivaroxaban dosing (at least for the first 30 days) . | Days to platelet recovery . | Study events* . |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Group A1 | |||||||||||
| 66 | F | 6 | 1.67 | 90 | CA-DVT | No | 107 | None | 20 mg once per day ≥30 days | 8 | None |
| 79 | F | 5 | 2.15 | 97 | CA-PE | No | 78 | None | 15 mg twice per day ×3 weeks; then 20 mg ≥30 days | 3 | None |
| 60 | F | 5 | 3.07 | 98† | Multiple myeloma flush‡ | No | 25 | None | 15 mg twice per day ×6 days; then 20 mg once per day ≥30 days | 17 | None |
| 64 | F | 8 | 2.35 | 100† | Multiple myeloma flush‡ | Upper limb DVT | 35 | None | 15 mg twice per day ×3 weeks; then 20 mg once per day ≥30 days | 12 | None |
| 94 | F | 7 | 2.48 | 97 | Hip fracture thromboprophylaxis§ | Lower limb DVT | 56 | None | 15 mg twice per day ×3 weeks; then 20 mg once per day ≥30 days | 4 | None |
| 62 | M | 6 | 1.66 | 92 | CA-DVT | No | 49 | None | 20 mg once per day ≥30 days | 3 | None |
| 72 | M | 7 | 2.08 | 100† | General surgery thromboprophylaxis | PE | 86 | None | 15 mg twice per day ×3 weeks; then 20 mg once per day ≥30 days | 4 | None |
| Group A2 | |||||||||||
| 83 | F | 6 | 2.17 | 95 | Hip fracture thromboprophylaxis§ | Bilateral adrenal hemorrhage | 415 | None | 10 mg once per day ≥30 days | NA | None |
| Group B | |||||||||||
| 54 | F | 6 | 2.10 | 100† | CA-DVT/PE | No | 64 | Fondaparinux ×1 day | 15 mg twice per day ×3 weeks; then 20 mg once per day ×3 days, then 10 mg once per day ≥30 days (chemotherapy-induced thrombocytopenia) | 7 | None |
| 69 | F | 8 | 2.48 | 100† | Post–coronary artery bypass grafting|| | Yes | 73 | Fondaparinux ×4 days | 15 mg twice per day ×12 weeks; then 20 mg once per day ≥30 days (see Figure 2) | 60 | None |
| Group C | |||||||||||
| 55 | F | 5 | 2.49 | 95 | Post–abdominal aortic aneurysm thromboprophylaxis | No | 163 | Fondaparinux ×5 days | 10 mg once per day ×17 days | NA | None |
| 78 | M | 6 | 2.89 | 97† | General surgery thromboprophylaxis | DVT | 203 | Argatroban ×3 days; Fondaparinux ×51 days | 20 mg once per day ≥30 days | NA | None |
| 56 | F | 5 | 1.28 | 84 | Medical prophylaxis | No | 332 | Fondaparinux ×11 days | 10 mg once per day ≥30 days | NA | None |
| 92 | F | 6 | 2.40 | 96 | Hip fracture thromboprophylaxis§ | No | 159 | Fondaparinux ×7 days | 10 mg once per day ≥30 days | NA | None |
| 72 | M | 5 | 1.11 | 91 | Post–coronary artery bypass grafting|| | No | 192 | Fondaparinux ×5 days | 20 mg once per day ≥30 days | NA | None |
| 74 | M | 6 | 2.82 | 97 | Post–aortic valve replacement|| | No | 361 | Fondaparinux ×10 days | 15 mg twice per day ×3 weeks; then 20 mg ≥30 days | NA | None |
| Patient age (years) . | Sex . | 4Ts score (points) . | EIA-IgG (OD units) . | Serotonin-release assay peak % release . | Patient clinical setting . | HIT-associated thrombosis . | Platelet count at rivaroxaban start . | Anticoagulant before rivaroxaban . | Rivaroxaban dosing (at least for the first 30 days) . | Days to platelet recovery . | Study events* . |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Group A1 | |||||||||||
| 66 | F | 6 | 1.67 | 90 | CA-DVT | No | 107 | None | 20 mg once per day ≥30 days | 8 | None |
| 79 | F | 5 | 2.15 | 97 | CA-PE | No | 78 | None | 15 mg twice per day ×3 weeks; then 20 mg ≥30 days | 3 | None |
| 60 | F | 5 | 3.07 | 98† | Multiple myeloma flush‡ | No | 25 | None | 15 mg twice per day ×6 days; then 20 mg once per day ≥30 days | 17 | None |
| 64 | F | 8 | 2.35 | 100† | Multiple myeloma flush‡ | Upper limb DVT | 35 | None | 15 mg twice per day ×3 weeks; then 20 mg once per day ≥30 days | 12 | None |
| 94 | F | 7 | 2.48 | 97 | Hip fracture thromboprophylaxis§ | Lower limb DVT | 56 | None | 15 mg twice per day ×3 weeks; then 20 mg once per day ≥30 days | 4 | None |
| 62 | M | 6 | 1.66 | 92 | CA-DVT | No | 49 | None | 20 mg once per day ≥30 days | 3 | None |
| 72 | M | 7 | 2.08 | 100† | General surgery thromboprophylaxis | PE | 86 | None | 15 mg twice per day ×3 weeks; then 20 mg once per day ≥30 days | 4 | None |
| Group A2 | |||||||||||
| 83 | F | 6 | 2.17 | 95 | Hip fracture thromboprophylaxis§ | Bilateral adrenal hemorrhage | 415 | None | 10 mg once per day ≥30 days | NA | None |
| Group B | |||||||||||
| 54 | F | 6 | 2.10 | 100† | CA-DVT/PE | No | 64 | Fondaparinux ×1 day | 15 mg twice per day ×3 weeks; then 20 mg once per day ×3 days, then 10 mg once per day ≥30 days (chemotherapy-induced thrombocytopenia) | 7 | None |
| 69 | F | 8 | 2.48 | 100† | Post–coronary artery bypass grafting|| | Yes | 73 | Fondaparinux ×4 days | 15 mg twice per day ×12 weeks; then 20 mg once per day ≥30 days (see Figure 2) | 60 | None |
| Group C | |||||||||||
| 55 | F | 5 | 2.49 | 95 | Post–abdominal aortic aneurysm thromboprophylaxis | No | 163 | Fondaparinux ×5 days | 10 mg once per day ×17 days | NA | None |
| 78 | M | 6 | 2.89 | 97† | General surgery thromboprophylaxis | DVT | 203 | Argatroban ×3 days; Fondaparinux ×51 days | 20 mg once per day ≥30 days | NA | None |
| 56 | F | 5 | 1.28 | 84 | Medical prophylaxis | No | 332 | Fondaparinux ×11 days | 10 mg once per day ≥30 days | NA | None |
| 92 | F | 6 | 2.40 | 96 | Hip fracture thromboprophylaxis§ | No | 159 | Fondaparinux ×7 days | 10 mg once per day ≥30 days | NA | None |
| 72 | M | 5 | 1.11 | 91 | Post–coronary artery bypass grafting|| | No | 192 | Fondaparinux ×5 days | 20 mg once per day ≥30 days | NA | None |
| 74 | M | 6 | 2.82 | 97 | Post–aortic valve replacement|| | No | 361 | Fondaparinux ×10 days | 15 mg twice per day ×3 weeks; then 20 mg ≥30 days | NA | None |
All 16 patients tested positive by immunoglobulin G (IgG)–specific EIA (median, 2.26 optical density [OD] units; range, 1.11-3.07 OD units) and by polyspecific EIA-IgGAM (median, 3.05 OD units; range, 1.55-4.11 OD units) (individual data for the EIA-IgGAM not shown). Of the 43 SRA-positive patients with probable HIT identified in the 3 Hamilton hospitals during the time frame of this study, 16 received rivaroxaban, and 10 could have received rivaroxaban (but were treated with an alternative anticoagulant, most often fondaparinux). The remaining 17 patients were ineligible to receive rivaroxaban (renal insufficiency, n = 7; intubated/critically ill, n = 5; withdrawal of care or death before SRA result became available, n = 4; treatment with phenytoin, n = 1). All patients in groups A and B were started on at least 20 mg/d (ie, 10 mg or 15 mg twice per day or 20 mg once per day), although the A2 patient was started on 10 mg/day (reflecting adrenal hemorrhage). Three of the six group C patients received 10 mg/d, with the remaining patients receiving larger doses.
CA-DVT, cancer-associated deep vein thrombosis; CA-PE, cancer-associated pulmonary embolism; DVT, deep vein thrombosis; EIA-GAM, polyspecific EIA that detects anti-PF4/polyanion antibodies of IgG, IgA, and/or IgM isotypes (PF4 Enhanced; Immucor GTI Diagnostics, Waukesha, WI); F, female; M, male; NA, not applicable; OD, optical density; PE, pulmonary embolism.
Study events include 30-day thrombosis event rate, thrombosis while receiving rivaroxaban, and major bleeding while receiving rivaroxaban (all 16 patients had follow-up until at least 30 days after starting rivaroxaban).
Indicates possible presence of heparin-independent (autoimmune) HIT antibodies, as shown by serotonin-release >50% even in the absence of heparin (ie, at 0 U/mL unfractionated heparin [buffer control]).
Multiple myeloma patients who were exposed to heparin only through heparin flushes for apheresis catheter management during stem cell harvesting for planned autologous stem cell transplantation.
Includes preoperative unfractionated heparin followed by postoperative low-molecular-weight heparin.
Performed using cardiopulmonary bypass.