Impact of platelet functional assays on the cost of treating suspected heparin induced thrombocytopenia (HIT)

Purpose: To determine the costs associated with the treatment of suspected HIT and to investigate the potential cost savings of functional platelet assays like the serotonin release assay (SRA) in the diagnosis of this condition.

Methods: We performed a retrospective cost of illness analysis of suspected HIT, which was defined as thrombocytopenia leading to heparin discontinuation, positive screen for heparin/platelet-factor 4 antibodies and treatment with a direct thrombin inhibitor (DTI). Direct medical costs were collected, including those associated with diagnostic testing, DTI treatment, and complications (bleeding and thrombosis). Patients with the SRA ordered as part of their diagnostic evaluation were compared to those who did not. The primary clinical endpoint was a composite of mortality and major bleed, defined by the International Society on Thrombosis and Haemostasis criteria.

Results: 147 patients were identified (61.2 ± 15.1 years, 49% female, 54.4% African American, 51.7% thrombosis). An SRA was ordered in 53 patients, of whom only 17% were positive. The average delay in reporting SRA results was 9 days. Overall, the use of the SRA did not reduce the total cost of treatment per patient ($7,954 vs. $7,136. p=0.331), length of stay (22 vs. 22 days. p= 0.486), or the composite primary clinical endpoint (32.1% vs. 33%. p=0.911). Early ordering of the SRA (within 48h) was associated with shorter length of stay (20 vs. 27 days. p=0.029) and a trend toward lower DTI duration (7.5 vs. 10 days. p=0.240) and primary endpoint (20.8% vs. 41.4%. p=0.442). A negative SRA led to the discontinuation of the DTI in 77.8% of patients, and subsequently 33.3% were discharged within 48h. 

Conclusion: The use of the SRA in the diagnosis of suspected HIT did not reduce costs or clinical outcomes in our overall analysis, however earlier availability of this test may impact therapy and reduce costs.