A high-value cost conscious approach to minimize heparin induced thrombocytopenia antibody (HITAb) testing using the 4T score

Abstract

Heparin Induced Thrombocytopenia (HIT) is a serious complication from administration of heparin products. The 4T score is a validated pre-test probability tool to screen for HIT in hospitalized patients. As the negative predictive value (NPV) is very high further testing for HIT in patients with a low score can be avoided. Our objective was to determine trends at our hospital with respect to utilization of HIT antibody (HITAb) testing and evaluate economic burden from unnecessary HIT testing. A retrospective cohort review was performed on patients age 18 and above admitted to a tertiary care center from February 2013 to December 2014 who underwent HITAb testing. Surgical ICU patients were excluded. Patients were stratified into low, intermediate, and high risk for HIT based on the 4T model. Statistical analysis was performed using Chi square and regression models. Of 150 patients that underwent HITAb testing, 134 met inclusion criteria. 73 were male (54.47 %) and mean age was 55.50 ± 17.27 years. 81 patients had a low 4T score 0-3. Analysis of testing trends showed 60.44 % of patients were tested for HITAb despite being low risk using the 4T model. Only three patients with low 4T score were positive on confirmatory SRA testing (NPV 96.29 % CI 95 = 89.56-99.23 %). Expenditure due to inappropriate testing and treatment was estimated at $103,348.13. The majority of HITAb testing was found unnecessary based on the investigator calculated 4T score. We propose implementation of an electronic medical record (EMR) based calculator in order to reduce unneeded tests and reduce use of costlier alternative anticoagulants.

Scoping Review of Interventions Associated with Cost Avoidance Able to Be Performed in the Intensive Care Unit and Emergency Department

“…Not sending the enzyme‐linked immunosorbent assay HITAb test in low‐risk patients would have resulted in a potential cost savings of $59,992.49 at a rate of $739.29 per test. Of the 81 patients at low risk, 3.7% tested positive for HIT, demonstrating a negative predictive value of 96.4% . Economic benefit was also demonstrated in a pharmacy‐driven anticoagulation model evaluating the appropriateness of HIT antibody tests ordered .…”

“…Of the 81 patients at low risk, 3.7% tested positive for HIT, demonstrating a negative predictive value of 96.4%. 31 Economic benefit was also demonstrated in a pharmacy-driven anticoagulation model evaluating the appropriateness of HIT antibody tests ordered. 32 Instances in which treatment with a non-heparinoid was avoided (e.g., direct thrombin inhibitor) through pharmacist intervention should also be considered as part of this category.…”

HITTING the Diagnosis

“…Heparin-induced thrombocytopenia (HIT) is a potentially lethal complication of therapy with unfractionated heparin or its derivatives. 1,2 HIT is caused by the development of antibodies directed against a molecular complex formed when heparin associates with endogenous platelet factor 4 (PF4). The formation of the heparin-PF4 immune complex leads to activation of platelets, monocytes, and endothelial cells with subsequent release of procoagulant proteins and tissue factor.…”

“…1,[3][4][5] The incidence of HIT has been reported to range from 0.1% to 5% in hospitalized patients exposed to unfractionated heparin. 2,6 HIT is a hypercoagulable state that can cause severe venous and arterial thromboembolic complications in patients. These complications may be associated with significant morbidity and even mortality.…”

“…8,9 The 4Ts score is a well-validated method used as a standardized approach to determine the pretest probability of HIT. 2,10 This score is especially useful to exclude HIT given its high negative predictive value of 99.8%. 10,11 Laboratory tests to help diagnose HIT include enzyme-linked immunosorbent assays (ELISA) that detect heparin-PF4 antibodies and platelet function assays such as the serotonin release assay (SRA), which is considered the gold standard in HIT testing.…”