Computerised risk scores to guide recognition and diagnosis in patients with possible heparin‐induced thrombocytopenia

Abstract

The heparin-induced thrombocytopenia computerised risk (HIT-CR) score is designed to aid in the diagnosis of HIT. We sought to evaluate its potential clinical utility. In this retrospective cohort study, we collected HIT-CR scores on all inpatients receiving heparin over a 4-month period and performed chart reviews on the subset who independently underwent clinical diagnostic testing for HIT to identify patients with HIT. In all, 34 342 patients received heparin, 1744 had high-risk HIT-CR scores of ≥3 and 220 had the maximal risk score of 4. Only 6% of high-risk and 10% of maximal-risk patients underwent testing for HIT. Conversely, among all 317 patients who underwent independent testing for HIT, 67% had low-risk HIT-CR scores (<3). Among patients independently tested, the positive predictive value (PPV) was 6Á6% [95% confidence interval (CI) 4Á9-8Á8%] and the negative predictive value (NPV) was 99Á5% (95% CI 97Á1-99Á9%) at a HIT-CR score cutoff of 3, and the PPV was 22Á7% (95% CI 12Á7-37Á4%) and NPV was 99Á0% (95% CI 97Á6-99Á6%) at a cutoff of 4. This study suggests clinicians fail to test most high-risk patients and unnecessarily test many low-risk patients for HIT. A reasonable approach to clinical application of HIT-CR scores would be recommending no testing for patients with a score of <3 and recommend testing for patients with a score of 4.

Diagnosing heparin‐induced thrombocytopenia: The need for accuracy and speed

“…The use of this EHR tool identified 220/34,342 patients with a maximum score of 4. The PPV of the short automated score at the proposed cutoff of 4 was 22.7% (95% CI 12.7%‐37.4%) and NPV was 99.0% (95% CI 97.6%‐99.6%) 33 . It is conceivable that use of the EHR to alert clinicians to the possibility of HIT may increase the speed of diagnosis by not relying solely on the busy clinical team to recognize the platelet trend among other complex patient issues.…”

“…A limitation of these clinical‐decision support tools was that they did not incorporate a key feature of the 4Ts score, “Timing” of the platelet count fall relative to heparin exposure 32 . Gallo et al devised a novel EHR tool that serves as an automated short‐version of the 4Ts score, which extracts both timing of platelet count fall and degree of thrombocytopenia 33 . The use of this EHR tool identified 220/34,342 patients with a maximum score of 4.…”

“…32 Gallo et al devised a novel EHR tool that serves as an automated short-version of the 4Ts score, which extracts both timing of platelet count fall and degree of thrombocytopenia. 33 The use of this EHR tool identified 220/34,342 patients with a maximum score of 4. The PPV of the short automated score at the proposed cutoff of 4 was 22.7% (95% CI 12.7%-37.4%) and NPV was 99.0% (95% CI 97.6%-99.6%).…”

“…The PPV of the short automated score at the proposed cutoff of 4 was 22.7% (95% CI 12.7%-37.4%) and NPV was 99.0% (95% CI 97.6%-99.6%). 33 It is conceivable that use of the EHR to alert clinicians to the possibility of HIT may increase the speed of diagnosis by not relying solely on the busy clinical team to recognize the platelet trend among other complex patient issues. Automated calculation should in theory improve interobserver variability, although there will likely be variation in clinicians' response to the EHR alerts.…”

Heparin-induced Thrombocytopenia: Perioperative Diagnosis and Management

“…The "computerized risk score" and the "Groupe Français Hémostase et Thrombose HIT score" have been developed recently, but additional validation is needed. 20,21 laboratory assays Screening Test for HIT: Direct Detection of HIT antibodies HIT antibodies can be directly measured using immunoglobulin G-specific immunoassays. 22 The classical test system The acute phase of heparin-induced thrombocytopenia is characterized by a sudden decrease in the platelet count and detection of platelet-activating antibodies in the functional assay.…”