Over-testing for heparin induced thrombocytopenia in hospitalized patients.

[heparin-induced thrombocytopenia]

Heparin induced thrombocytopenia (HIT ) is a pro-thrombotic and potentially fatal complication of heparin therapy . Its diagnosis rests on high clinical probability and the laboratory demonstration of anti-PF 4 /heparin antibodies . The high prevalence of thrombocytopenia in hospitalized patients and the high sensitivity but low specificity of immunoassays for HIT antibodies can lead to over-testing and over-diagnosis . We conducted a study to review HIT screening practices in a tertiary care setting . We reviewed 63 consecutive patients undergoing testing for anti-PF 4 /heparin antibodies over 3 months . Pre-test probability for HIT was calculated using the 4 T score . Sixty three patients underwent testing for anti-PF 4 /heparin antibodies . Twenty one had been admitted for cardiovascular surgery , 5 for other surgery and 35 for non-surgical indications . Twenty nine patients (46 %) had low pre- test probability , twenty three (36 .5 %) had intermediate probability , and eleven (17 .4 %) had high pre-test probability of having HIT . Anti-PF 4 /heparin ELISA was positive in 8 of 63 patients . SRA was ordered for 16 patients and was positive in 5 . Only five patients were diagnosed and treated for HIT . Over-testing for HIT is highly prevalent in a tertiary care setting . This increases cost and exposes patients to expensive anti-coagulation with its attendant risk of hemorrhage . The 4 Ts score has been shown to have high sensitivity and may be used to rule out HIT in most situations , although its utility depends on subjective analysis . Consistently applying this in practice could minimize over-testing and facilitate safer , cost-effective care .