Correlation of ELISA optical density with clinical diagnosis of heparin-induced thrombocytopenia: a retrospective study of 104 patients with positive anti-PF4/heparin ELISA.

BACKGROUND

Enzyme-linked immunosorbent assay (ELISA) for antiplatelet factor 4 (anti-PF4)/heparin antibodies is expressed in terms of optical density (OD). Previous studies have shown correlation between OD and heparin-induced thrombocytopenia (HIT) diagnosis. However, these were mainly laboratory based.

OBJECTIVE

Retrospective correlation of clinical HIT to ELISA OD.

PATIENTS/METHODS: We conducted a retrospective study involving 104 patients with a positive ELISA for anti-PF4/heparin antibodies between 2008 and May 2012. For each patient, a clinical diagnosis was adjudicated based on different features including "4T scores," laboratory results, and a 3-month clinical follow-up.

RESULTS

In this study, 28.8% of the patients were HIT positive, and 71.2% HIT negative. Patients with positive diagnosis had significantly higher mean OD (2.15 ± 0.76 vs 0.83 ± 0.62). Patients with OD <1.0 only had 3.4% positive diagnosis versus 45.5% for OD 1.0 to 2.0 and 78% for >2.0 units.

CONCLUSION

This study is a clinical confirmation that ELISA OD results are correlated with the probability of a clinical diagnosis of HIT.