Objectives To investigate the incidence of the heparin-induced thrombocytopenia (HIT) and positivity of anti-heparin/platelet factor 4 complex antibody (HIT-antibody) in inpatients treated with heparin preparations.Methods A total of 197 consecutive patients,including 120 men and 77 women,who were treated with unfractioned heparin (UFH) or low molecular weight heparin (LMWH),were enrolled in this study.HIT-antibody was detected by enzyme-linked immunosorbent assay (ELISA).All patients were classified into subgroups based on 4Ts (Pretest Clinical Scoring System) and types of underlying disorders.The incidence of HIT and positivity of HIT-antibody among different groups were analyzed.Results The overall incidence of HIT was 3.0％ (6/197),and the positivity of HIT antibody was 12.2％ (24/197).The positivity of HIT-antibody was 10.1％ (18/178),7.7％ (1/13) and 83.3％(5/6) in low,moderate and high HIT probability group respectively.There were significant differences of HIT positivity and mean level of HIT-antibody between the high HIT probability group and the low or moderate HIT probability group (P =0.000).Both the incidence of HIT and positivity of HIT-antibody were higher in surgical patients than in medical patients (5.8％ vs 0.9％,P =0.047 and 19.8％ vs 6.3％,P =0.004).Conclusions The incidence of HIT and positivity of HIT-antibody were 3.0％ and 12.2％ respectively,both of which were related with the types of disorders.Detection of HIT-antibody has a better applicable value in patients with high HIT probability.