What is the efficacy of immunoassays for the diagnosis of heparin-induced thrombocytopenia (HIT)?

Updated: Sep 10, 2021
  • Author: Sancar Eke, MD, FASN; Chief Editor: Srikanth Nagalla, MD, MS, FACP  more...
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Baroletti and colleagues found that in patients with clinically suspected HIT, a 1-unit increase in optical density values was associated with an approximate doubling in the odds of thrombosis by 30 days (odds ratio, 1.9; 95% confidence interval, 1.5-2.6; P=.0001). The proportion of patients with pulmonary embolism increased with higher values. [51]

In a study of surgical intensive care unit (ICU) patients, Berry and colleagues found that only 19% of patients with an optical density value of 0.4 or higher had a positive SRA result. Use of an optical density threshold of 2.0 proved more predictive of HIT, with a true positive rate of 65%. [47] Another study of surgical ICU patients, by Barada and colleagues, also recommended an optical density threshold of 2.0 or more, to reduce overdiagnosis and overtreatment. [46]

One proposed procedure to improve the specificity of the ELISA involves the addition of excess heparin to the sample. With a positive ELISA, a decrease in the optical density by 50% or more after the addition of excess heparin confirms the presence of heparin-dependent antibodies.

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