Detection And Evaluation Of Hit-antibody In Patients Treated With Heparin Preparations

ObjectivesTo investigate the incidence of the heparin-induced thrombocytopenia (HIT) and positivity of anti-heparin/platelet factor 4 complex antibody (HIT-antibody) in hospitalized patients treated with unfractionated heparin (UFH) or low molecular weight heparin (LMWH), and evaluate the correlationship between HIT-antibody determined by enzyme-linked immunosorbent assay (ELISA) and the clinical diagnosis of HIT by the "4Ts" pretest scoring system.Methods197 consecutive patients, including 120 males and 77 females, who were admitted into Sino-Japan Friendship Hospital and Peking Union Medical College Hospital and treated with unfractioned heparin (UFH) or low molecular weight heparin (LMWH), were enrolled in our study from November,2008 to May,2009.30 healthy objects who unexposed to heparin were enrolled to establish the normal limits of HIT-antibody assay. Two different kinds of ELISA kits were utilized to detect the HIT-antibody. All the patients were classified into different subgroups based on "4Ts" Pretest Clinical Scoring System and types of disorders. The positivity of HIT antibody among different groups were analyzed, and the sensitivity and specificity were compared betweent two kinds of HIT-antibody assay.ResultsThrombocytopenia occurred in twenty two of 197 patients (11.2%) after receiving treatment of UFH or LMWH. Six of the 22 thrombocytopenic patients were diagnosed as HIT according to the "4Ts" scoring system, and the incidence of HIT was 3.05%. Five of the 6 HIT patients were positive by USNLIFE-ELISA (U-HIT) antibody assay, but none positive by BIOWORD-ELISA (B-HIT) antibody assay. The sensitivity was 83.3% by U-HIT assay and,0% by B-HIT assay. Twenty four of 197 patients (12.18%) were positive by U-HIT antibody assay, in whom 5 patients were diagnosed as HIT according to "4Ts" scoring system. Five of 197 patients (2.54%) were positive by B-HIT antibody assay, in whom none was diagnosed as HIT according to "4Ts" scoring system. The specificity was 90.0% by U-HIT antibody assay and is,97.4% by B-HIT antibody assay.The positivity of U-HIT antibody was 10.1%,7.7% and 83.3%, respectively in low, moderate and high HIT probability group. There were significant differences of HIT positivity and mean level of HIT antibody between the group of high HIT probabilityand the group of low or moderate HIT probability, both P=0.000. The positivity of HIT-antiby is higher in surgical patients than in medical patients, P=0.004. There were no correlations between the HIT positivity and either of genders, ages, previous exposure of UFH or LMWH, and types of heparin preparations, P=0.470,0.528,0.798, and 0.768.ConclusionsThe overall incidence of HIT was 3.05% in our study, which is identical to the most reports from other studies. Because of a lack of standard of HIT-antibody assay, marked differences were existed in sensitivity and specificity of HIT antiboday assays among different studies The sensitivity and specificity of U-HIT antibody assay were 83.3% and 90.0% respectively, and could be used to assist the diagnosis of HIT. "4Ts" scoring system is still the most important and applied criteria to clinical diagnosis of HIT at present.