title: Pediatric heparin-induced thrombocytopenia: prevalence, thrombotic risk, and application of the 4Ts scoring system.
abstract: OBJECTIVE
  To 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.
  
  
  METHODS
  In 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.
  
  
  RESULTS
  The 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.
  
  
  CONCLUSIONS
  The 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.
authors.affiliation: Division of Hematology/Oncology, Boston Children's Hospital, Boston, MA; Department of Pediatric Oncology, Dana-Farber Cancer Institute and Harvard Medical School, Boston, MA.
authors.forename: Esther A
authors.initials: EA
authors.lastname: Obeng
authors.affiliation: Division of Hematology/Oncology, Boston Children's Hospital, Boston, MA.
authors.forename: Kathy M
authors.initials: KM
authors.lastname: Harney
authors.affiliation: Department of Pharmacy, Boston Children's Hospital, Boston, MA.
authors.forename: Thomas
authors.initials: T
authors.lastname: Moniz
authors.affiliation: Department of Pharmacy, Boston Children's Hospital, Boston, MA.
authors.forename: Alana
authors.initials: A
authors.lastname: Arnold
authors.affiliation: Division of Hematology/Oncology, Boston Children's Hospital, Boston, MA; Department of Pediatric Oncology, Dana-Farber Cancer Institute and Harvard Medical School, Boston, MA.
authors.forename: Ellis J
authors.initials: EJ
authors.lastname: Neufeld
authors.affiliation: Division of Hematology/Oncology, Boston Children's Hospital, Boston, MA; Department of Pediatric Oncology, Dana-Farber Cancer Institute and Harvard Medical School, Boston, MA. Electronic address: cameron.trenor@childrens.harvard.edu.
authors.forename: Cameron C
authors.initials: CC
authors.lastname: Trenor
mesh_terms: D000293:Adolescent; D001900:Boston; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D005260:Female; D005343:Fibrinolytic Agents / Q000009:adverse effects*; D006493:Heparin / Q000009:adverse effects*; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D015995:Prevalence; D012189:Retrospective Studies; D012307:Risk Factors; D012680:Sensitivity and Specificity; D013921:Thrombocytopenia / Q000139:chemically induced* / Q000175:diagnosis / Q000453:epidemiology; D013927:Thrombosis / Q000139:chemically induced*; D055815:Young Adult
chemical_list: D005343:Fibrinolytic Agents; D006493:Heparin