Platelet factor 4/heparin-particle gel immunoassay (PaGIA) is a weak method for heparin-induced thrombocytopenia (HIT) evaluation of post cardio-pulmonary bypass surgery patients.

[heparin-induced thrombocytopenia]

Diagnosis of heparin induced thrombocytopenia (HIT ) is not always easy , especially when a confirmatory functional test is not available . In most cases the diagnosis relies on the combination of pretest probability and an immunologic test . Among patients post cardiopulmonary bypass (CPB ) surgery , anti-platelet factor 4 /heparin antibodies tend to be high but with low clinical implication . The current retrospective study examined the behavior of patients with positive PF 4 /heparin-PaGIA results , divided into two groups according to whether or not they have undergone CPB surgery . The main focus of the study was on the reliability of the PF 4 /heparin-PaGIA test in these two settings . The files of 104 single center patients , who had a positive PF 4 /heparin-PaGIA test , were reviewed . 62 % were post CPB and 38 % were not . An association between the intensity of positivity of PF 4 /heparin-PaGIA test and both the 4 Ts pretest probability method (p = 0 .003 ) and the incidence of thrombosis (p = 0 .02 ) was found only in the patients who have not undergone CPB surgery , but not in the CPB patients . This study suggests that PF 4 /heparin-PaGIA is not a reliable method in patients post CPB surgery who are investigated for a possible diagnosis of HIT .