Division of Hematology/Oncology, Drexel University College of Medicine/Hahnemann University Hospital, Philadelphia, PA 19102, USA.
Postgrad Med. 2012 Nov;124(6):36-42. doi: 10.3810/pgm.2012.11.2611.
The initial diagnosis of heparin-induced thrombocytopenia (HIT) is made on clinical grounds because the assays with the highest sensitivity (eg, heparin-platelet factor 4 antibody enzyme-linked immunosorbent assay [ELISA]) and specificity (eg, serotonin release assay) may not be readily available. The clinical utility of the pretest scoring system, the 4Ts, was developed and validated by Lo et al in the Journal of Thrombosis and Haemostasis in 2006. The pretest scoring system looks at the degree and timing of thrombocytopenia, thrombosis, and the possibility of other etiologies. Based on the 4T score, patients can be categorized as having a high, intermediate, or low probability of having HIT. We conducted a retrospective study of 100 consecutive patients who were tested for HIT during their hospitalization at Hahnemann University Hospital (Philadelphia, PA) in 2009. Of the 100 patients analyzed, 72, 23, and 5 patients had 4T pretest probability scores of low, intermediate, and high, respectively. A positive HIT ELISA (optical density > 1.0 unit) was detected in 0 of 72 patients (0%) in the low probability group, in 5 of 23 patients (22%) in the intermediate probability group, and in 2 of 5 patients (40%) in the high probability group. The average turnaround time for the HIT ELISA was 4 to 5 days. Fourteen (19%) of the 72 patients with a low pretest probability of HIT were treated with a direct thrombin inhibitor. Ten (71%) of the 14 patients in the low probability group treated with a direct thrombin inhibitor had a major complication of bleeding requiring blood transfusion support. In this retrospective study, a low 4T score showed 100% correlation with a negative HIT antibody assay. We recommend incorporating the 4T scoring system into institutional core measures when assessing a patient with suspected HIT, selecting only patients with intermediate to high probability for therapeutic intervention, which may translate into reduced morbidity and lower health care costs.
肝素诱导的血小板减少症（HIT）的初始诊断基于临床依据，因为灵敏度最高的检测方法（如肝素-血小板因子 4 抗体酶联免疫吸附试验 [ELISA]）和特异性（如血清素释放试验）可能无法立即获得。预测试评分系统（4Ts）的临床应用是由 Lo 等人于 2006 年在《血栓与止血杂志》上开发和验证的。该预测试评分系统着眼于血小板减少症、血栓形成的程度和时间以及其他病因的可能性。根据 4T 评分，患者可以分为 HIT 发生可能性高、中、低的风险类别。我们对 2009 年在 Hahnemann 大学医院（费城，宾夕法尼亚州）住院期间接受 HIT 检测的 100 例连续患者进行了回顾性研究。在分析的 100 例患者中，分别有 72、23 和 5 例患者的 4T 预测试概率评分为低、中、高。在低概率组中，0 例（0%）患者的 HIT ELISA（光密度>1.0 单位）呈阳性，在中概率组中，23 例患者中有 5 例（22%）呈阳性，在高概率组中，5 例患者中有 2 例（40%）呈阳性。HIT ELISA 的平均周转时间为 4 至 5 天。在低 HIT 预测试概率组中，有 72 例（19%）患者接受了直接凝血酶抑制剂治疗。在低概率组中接受直接凝血酶抑制剂治疗的 14 例患者中，有 10 例（71%）出现需要输血支持的严重出血并发症。在这项回顾性研究中，低 4T 评分与 HIT 抗体检测阴性呈 100%相关性。我们建议在评估疑似 HIT 的患者时将 4T 评分系统纳入机构核心措施中，仅选择中、高概率患者进行治疗干预，这可能会降低发病率和降低医疗保健成本。
