• Esther A Obeng, Kathy M Harney, Thomas Moniz, Alana Arnold, Ellis J Neufeld, and Cameron C Trenor.
• Division of Hematology/Oncology, Boston Children's Hospital, Boston, MA; Department of Pediatric Oncology, Dana-Farber Cancer Institute and Harvard Medical School, Boston, MA.
• J. Pediatr. 2015 Jan 1;166(1):144-50.

ObjectiveTo characterize heparin-induced thrombocytopenia (HIT) at a single pediatric center including the prevalence and the accuracy of the 4Ts scoring system as a predictor of HIT.Study DesignIn this retrospective cohort study, we identified 155 consecutive patients <21 years old with sufficient data for 4Ts scoring. The 4Ts scoring system is a validated pretest tool in adults that predicts the likelihood of HIT using clinical features. Hospital-wide exposure to unfractionated and low molecular weight heparin was determined by querying the hospital pharmacy database.ResultsThe majority of patients with suspected HIT (61.2%) were on surgical services. Prediction of HIT risk using initial 4Ts scoring found 3 (2%) had high risk 4Ts scores, 114 (73%) had intermediate risk 4Ts scores, and the remaining 38 (25%) had low risk 4Ts scores. HIT was confirmed in 0/38 patients with low risk 4Ts scores, 2/114 patients with intermediate-risk 4Ts scores, and all 3 patients with high-risk 4Ts scores presented with HIT with thrombosis. Of 12 positive HIT screening tests, results were falsely positive in 66.6% of patients with intermediate risk 4Ts scores and 100% of patients with low risk 4Ts scores. The prevalence of HIT was 0.058% and HIT with thrombosis was 0.046% in pediatric patients on unfractionated heparin.ConclusionsThe prevalence of HIT appears significantly lower in pediatric patients compared with adults. Application of the 4Ts system as a pretest tool may reduce laboratory evaluation for HIT in heparin-exposed children with low risk 4Ts scores, decreasing unnecessary further testing, intervention, and cost.Copyright © 2015 Elsevier Inc. All rights reserved.

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