Comparison of a clinical-laboratory algorithm, 4t and heparin-induced thrombocytopenia expert probability scores in the diagnosis of heparin-induced thrombocytopenia in the critical care setting.

backgroundSeveral scoring systems are utilized to calculate the pre-test probability of heparin-induced thrombocytopenia (HIT). We hypothesize that a clinical-laboratory algorithm combining the 4Ts score with the optical density (OD) of anti-PF4-heparin antibody is more accurate than either the 4Ts or HIT expert probability (HEP) scores in the critical care setting.

methodsA single-institution retrospective review of adult patients admitted to the intensive care unit (ICU) that were evaluated for HIT was conducted. Two reviewers independently rated the proposed algorithm, 4Ts and HEP score. Summary, univariate and area under receiver operator characteristic analyses were performed.

resultsA total of 88 patients with a mean (SD) age of 62 (15) years were included. The sensitivity, positive predictive value and negative predictive value were superior in our clinical-laboratory algorithm compared to the 4Ts score ≥ 4 and the HEP score ≥ 2. The algorithm's specificity was non-inferior to the 4Ts score and HEP score. There was no significant difference between our clinical-laboratory algorithm and the 4Ts score or the HEP score in predicting HIT.

conclusionOur study confirms that the combination of clinical and laboratory criteria is crucial in the presumable diagnosis of HIT. This is the first study that validates different HIT scores in an isolated ICU population.