The HIT Expert Probability (HEP) Score: a novel pre‐test probability model for heparin‐induced thrombocytopenia based on broad expert opinion

Abstract

Expert Probability (HEP) Score: a novel pre-test probability model for heparin-induced thrombocytopenia based on broad expert opinion. J Thromb Haemost 2010; 8: 2642-50.Summary. Background: The diagnosis of heparin-induced thrombocytopenia (HIT) is challenging. Over-diagnosis and over-treatment are common. Objectives: To develop a pre-test clinical scoring model for HIT based on broad expert opinion that may be useful in guiding clinical decisions regarding therapy. Patients/methods: A pre-test model, the HIT Expert Probability (HEP) Score, was constructed based on the opinions of 26 HIT experts. Fifty patients referred to a reference laboratory for HIT testing comprised the validation cohort. Two hematology trainees scored each patient using the HEP Score and a previously published clinical scoring system (4 TÕs). A panel of three independent experts adjudicated the 50 patients and rendered a diagnosis of HIT likely or unlikely. All subjects underwent HIT laboratory testing with a polyspecific HIT ELISA and serotonin release assay (SRA). Results: The HEP Score exhibited significantly greater interobserver agreement [intraclass correlation coefficient: 0.88 (95% CI 0.80-0.93) vs. 0.71 (0.54-0.83)], correlation with the results of HIT laboratory testing and concordance with the diagnosis of the expert panel (area under receiver-operating curve: 0.91 vs. 0.74, P = 0.017) than the 4 TÕs. The model was 100% sensitive and 60% specific for determining the presence of HIT as defined by the expert panel and would have allowed for a 41% reduction in the number of patients receiving a direct thrombin inhibitor (DTI). Conclusion: The HEP Score is the first pre-test clinical scoring model for HIT based on broad expert opinion, exhibited favorable operating characteristics and may permit clinicians to confidently reduce use of alternative anticoagulants. Prospective multicenter validation is warranted.

Relationship between the 4Ts scoring system and the antiplatelet factor 4/heparin antibodies test in critically ill patients

“…30 The positive predictive value of the 4Ts score was as low as 15.4%, a value less than the previously reported range from 21.4% to 100%. [8][9][10]15,[22][23][24][25][26] The false-positive rate of the 4Ts score (percentage of "4T high score" patients in the non-HIT patients) was 11.8%, a value comparable to those previously reported (0-15.3%). [8][9][10]15,[22][23][24][25][26] In contrast, the false-negative rate of the 4Ts scores (percentage of "4T low score" patients in HIT patients) was 54.5% (6/11), a value considerably higher than those previously reported (0-25%).…”

“…[8][9][10]15,[22][23][24][25][26] The false-positive rate of the 4Ts score (percentage of "4T high score" patients in the non-HIT patients) was 11.8%, a value comparable to those previously reported (0-15.3%). [8][9][10]15,[22][23][24][25][26] In contrast, the false-negative rate of the 4Ts scores (percentage of "4T low score" patients in HIT patients) was 54.5% (6/11), a value considerably higher than those previously reported (0-25%). [8][9][10]15,[22][23][24][25][26] These findings suggested that many individuals might develop HIT even with a low 4Ts score.…”

“…9 High negative predictive values ranging from 91.4% to 100% have been reported in subsequent studies carried out in medical-surgical ICU patients and cardiothoracic surgical patients. [8][9][10]15,[22][23][24][25][26] In the present study, a high negative predictive value of 4Ts score, 87.5%, was obtained for HIT, similarly to the previous studies mentioned above. This value was still lower than the values ranging from 91.4% to 100% in previous reports.…”

“…[8][9][10]15,[22][23][24][25][26] In contrast, the false-negative rate of the 4Ts scores (percentage of "4T low score" patients in HIT patients) was 54.5% (6/11), a value considerably higher than those previously reported (0-25%). [8][9][10]15,[22][23][24][25][26] These findings suggested that many individuals might develop HIT even with a low 4Ts score.…”

Experts’ opinion or the serotonin release assay as a gold standard for the diagnosis of heparin‐induced thrombocytopenia (HIT)?

“…In many studies regarding patients with a clinical suspicion of HIT, SRA is used as the Ôgold standardÕ for HIT diagnosis. Recently, the diagnosis of HIT was for the first time based on the opinion of three independent experts [5] blinded to the results of both SRA (performed using the method described by Sheridan et al) and IA. Surprisingly, it is reported in this study that both sensitivity and specificity of SRA were lower (71.4% [29-96.3] and 93% [80.9-98.5], respectively with 95% confidence intervals [CI]).…”