Lo G K, Juhl D, Warkentin T E, Sigouin C S, Eichler P, Greinacher A
Department of Medicine, McMaster University, Hamilton, ON, Canada.
J Thromb Haemost. 2006 Apr;4(4):759-65. doi: 10.1111/j.1538-7836.2006.01787.x.
Heparin-induced thrombocytopenia (HIT) is a prothrombotic adverse drug reaction caused by heparin. As thrombocytopenia is common in hospitalized patients receiving heparin, it would be useful to have a clinical scoring system that could differentiate patients with HIT from those with other reasons for thrombocytopenia.
To compare prospectively the diagnostic utility of a clinical score for HIT in two different clinical settings.
The pretest clinical scoring system, the '4 T's', was used to classify 100 consecutive patients referred for possible HIT in one hospital (Hamilton General Hospital, HGH) into high, intermediate, and low probability groups. This system was also used to classify likewise 236 patients by clinicians in Germany referring blood for diagnostic testing for HIT in Greifswald (GW). The clinical scores were correlated with the results of laboratory testing for HIT antibodies using the serologic criteria for HIT with high diagnostic specificity.
In both centers, patients with low scores were unlikely to test positive for HIT antibodies [HGH: 1/64 (1.6%), GW: 0/55 (0%)]. Patients with intermediate [HGH: 8/28 (28.6%), GW: 11/139 (7.9%)] or high scores [HGH: 8/8 (100%), GW: 9/42 (21.4%)] were more likely to test positive for clinically significant HIT antibodies. The positive predictive value of an intermediate or high clinical score for clinically significant HIT antibodies was higher at one center (HGH).
A low pretest clinical score for HIT seems to be suitable for ruling out HIT in most situations (high-negative predictive value). The implications of an intermediate or high score vary in different clinical settings.
肝素诱导的血小板减少症（HIT）是一种由肝素引起的促血栓形成的药物不良反应。由于血小板减少症在接受肝素治疗的住院患者中很常见，因此拥有一种能够区分HIT患者与其他血小板减少原因患者的临床评分系统将很有帮助。
前瞻性比较HIT临床评分在两种不同临床环境中的诊断效用。
使用预测试临床评分系统“4T's”，将一家医院（汉密尔顿综合医院，HGH）连续转诊的100例疑似HIT患者分为高、中、低概率组。德国的临床医生也使用该系统对236例在格赖夫斯瓦尔德（GW）进行HIT诊断检测的血液样本进行了类似分类。临床评分与使用具有高诊断特异性的HIT血清学标准进行的HIT抗体实验室检测结果相关。
在两个中心，低分患者不太可能检测出HIT抗体呈阳性[HGH：1/64（1.6%），GW：0/55（0%）]。中等[HGH：8/28（28.6%），GW：11/139（7.9%）]或高分[HGH：8/8（100%），GW：9/42（21.4%）]患者更有可能检测出具有临床意义的HIT抗体呈阳性。中等或高临床评分对具有临床意义的HIT抗体的阳性预测值在一个中心（HGH）更高。
HIT的低预测试临床评分似乎适用于在大多数情况下排除HIT（高阴性预测值）。中等或高评分的意义在不同的临床环境中有所不同。
