Optimizing Heparin Induced Thrombocytopenia Risk Assessment: Investigating the Role of the 4Ts Score After Lung Transplantation

ABSTRACT Background Heparin induced thrombocytopenia (HIT) is often suspected among lung transplant recipients (LTRs) due to a high prevalence of thrombocytopenia and frequent heparin use. This study explores the utility of the 4Ts score in stratifying HIT risk among adult LTRs. Methods LTRs from a single large transplant center with post‐transplant platelet factor 4 (PF4) antibody testing between January 2020 and June 2024 were included in the analysis. The 4Ts score was calculated retrospectively, and the risk of HIT was classified as low (4Ts score ≤3), intermediate (4–5), or high (≥6). The 4Ts risk classification was correlated with HIT laboratory testing results, with a positive serotonin release assay (SRA) representing confirmed HIT. Results A total of 205 LTRs were included. The median 4Ts score was 2 (IQR 2–4), 153 patients (74.6%) were classified as low risk, and 52 (25.4%) were intermediate or high risk. Among low‐risk patients, none had confirmed HIT. In contrast, among intermediate or high‐risk patients, six had HIT (11.5%), representing an overall incidence of 2.9%. Using a low 4Ts score to rule out HIT would have averted 153 PF4 tests (75% of total), 17 SRA tests (50% of total), and nine orders for direct thrombin inhibitors (53% of total). Conclusion A low 4Ts score ruled out HIT among LTRs at our large transplant center. Incorporating the 4Ts clinical risk assessment into the diagnostic process may help avoid unnecessary HIT testing and use of alternative anticoagulation.