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Heparin-Induced Thrombocytopenia in a Pediatric Population: Implications for Clinical Probability Scores and Testing
Laura Avila1, Nour Amiri2, Paul Yenson2
1Division of Hematology/Oncology, Department of Pediatrics, The Hospital for Sick Children, Toronto, Ontario, Canada; Child Health Evaluative Sciences, The Hospital for Sick Children, Toronto, Ontario, Canada.
Insights
The modified 4Ts score is more suitable for assessing Heparin-Induced Thrombocytopenia (HIT) risk in children than the HEP score. Although many children may be exposed to heparinoids, confirmed HIT cases are rare in pediatric populations.
Area of Science:
- Pediatric Hematology
- Thrombosis and Hemostasis
Background:
- Heparin-Induced Thrombocytopenia (HIT) is a serious immune-mediated complication of heparin therapy.
- Accurate risk assessment in pediatric patients is crucial but challenging due to limited data and modified scoring systems.
Purpose of the Study:
- To evaluate the applicability of the 4Ts score and the Heparin-Induced Thrombocytopenia (HIT) Expert Probability (HEP) score in diagnosing HIT in children.
- To estimate the number of pediatric patients potentially at risk for HIT.
Main Methods:
- Retrospective analysis of 50 children screened for HIT using enzyme immunoassay (EIA).
- Original and modified 4Ts scores were calculated, alongside the HEP score.
- Positive EIA results were confirmed with serotonin release assay (SRA).
Main Results:
- The modified 4Ts score identified a higher proportion of low-risk patients (86%) compared to the original 4Ts score (78%).
- A significant portion of children (54%) had a HEP score of ≥2, indicating intermediate to high risk.
- Despite 12% of patients having positive EIA results, none were confirmed positive by SRA, suggesting a low incidence of true HIT.
Conclusions:
- The modified 4Ts score appears more appropriate for pretest probability assessment of HIT in pediatric patients than the HEP score.
- While potential exposure to heparinoids is noted, confirmed HIT remains a rare diagnosis in children.
Objectives:
To determine the applicability of the 4Ts score and the Heparin-Induced Thrombocytopenia (HIT) Expert Probability (HEP) score in children with suspected HIT and to estimate the number of children potentially at risk of HIT.
Study Design:
We retrospectively estimated 4Ts and HEP scores in a cohort of 50 children referred for laboratory screening with enzyme immunoassay. In addition, minor modifications were introduced to the 4Ts score (modified 4Ts score) to adapt it for use in the pediatric setting. All patients with positive enzyme immunoassays were tested with serotonin release assay. We also extracted the number of patients started on heparins in a similar period of time.
Results:
The median age at the time of testing was 4 years (25th-75th percentile, 8.7 months to 13.5 years); 78% of patients had low and 22% had intermediate risk pretest probability scores using the original 4Ts score; 86% had low risk and 14% had intermediate risk scores using the modified 4Ts score; 54% of children had a HEP score of ≥2. Six patients (12%) had a positive (≥0.40 optical density units) enzyme immunoassay, but none had a positive serotonin release assay. Based on anticoagulation dose, there were 1-2 new daily potentially high-risk exposures to heparinoids at our institution.
Conclusions:
The modified 4Ts and original 4Ts scores may be more adequate than the HEP score to determine HIT pretest probability in children. Despite the number of patients potentially at risk, HIT is rare in pediatrics.
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