Diagnostic Performance of Heparin-Platelet Factor 4 Antibodies in the Identification of Heparin-Induced Thrombocytopenia in Cancer Population

Introduction: Cancer patients appear to have a higher risk of heparin induced thrombocytopenia (HIT) related complications than non-cancer patients; yet data on the performance of conventional diagnostic tools for HIT in cancer is limited.

Our aim was to determine among cancer patients with a 4T score ≥ 4, the performance of the conventional cut-off for HIT antibody testing (IgG anti PF4) to discriminate between serotonin release assay (SRA) positive and negative cases.

Methods: Retrospective and prospective analysis of cases (2002-2019) was performed of the electronic medical records of adult cancer patients at MD Anderson Cancer Center with suspected HIT. Cases were included in the analysis if the 4T score was ≥ 4 and investigated with IgG anti-PF4 optical density (HIT OD) and SRA.

Logistic regression model and the receiver operating characteristic curves were conducted to identify the sensitivity and specificity of different cut-off points for the HIT OD to discriminate HIT cases based on the SRA status.

Results: Among 50 cases, 18 were SRA positive. Median HIT OD was 1.03. At a cut-off point of 0.4, the HIT OD performed with a sensitivity of 0.89 and a specificity of 0.50 to discriminate the cases of SRA positive HIT. When the cut-off HIT OD was 1.0, the sensitivity was 0.78 with a specificity of 0.66.

Conclusions: Our findings suggest that in cancer patients the performance of IgG anti-PF4 is similar to that of non-cancer patients for the identification of HIT cases.