Prospective multicenter comparison of the diagnostic value of IgG and IgGAM antibodies for heparin-induced thrombocytopenia.

BACKGROUND AND AIMS: Heparin-induced thrombocytopenia (HIT) is a critical complication of heparin therapy. Immune antibodies are involved in the development of HIT. The purpose of this study was to explore the diagnostic value of IgGAM and IgG antibodies.

MATERIALS AND

METHODS

This prospective multicenter cohort study enrolled 170 patients with suspected HIT and 120 healthy volunteers. HIT was suspected when the complete blood count indicated a reduced platelet count. The presence of HIT was determined according to the clinical condition and laboratory results of patients. Parameters examined included conventional coagulation tests and IgG and IgGAM antibodies.

RESULTS

Among 170 patients with suspected HIT, 69 were PF4/H-antibody-positive (Ab+ patients), and 12 were diagnosed with HIT. Ab+ patients had higher levels of 4T score, D-dimer, and platelet reduction ratio than Ab- patients (P < 0.001 for all). We defined a HIT antibody risk index (HARI) as 0.807 × 4T score+ 0.028 × platelet reduction ratio (%)+ 0.114 × D-dimer (mg/l FEU), and found that the area under the curve (AUC) for HARI was greatest (0.857). Furthermore, the levels of IgGAM and IgG antibodies were higher in patients with HIT than without (P = 0.003 and P < 0.001, respectively). The AUC for IgG antibody was significantly greater than that for IgGAM antibody (0.870 vs. 0.775).

CONCLUSIONS

HARI can serve as a potential predictor for the risk of PF4/H-antibody positivity in patients with suspected HIT pre-test. For high-risk patients, IgG antibody testing may be used as a potential exclusion diagnostic indicator for patients with suspected HIT.