2025 Southeastern Residency Conference

Title: Correlation of 4T, m4T, and LLL Scores with Positive Heparin-induced Platelet Antibodies and Serotonin Release Assays in Cardiac Surgery ICU Patients
 
Authors: Alese Photiadis, Michelle Dillon, Danielle McPherson
 
Objective: Evaluate the accuracy of diagnostic scoring tools used to predict heparin-induced thrombocytopenia (HIT) in cardiac surgery (CS) and mechanical circulatory support (MCS) patients.
 
Background/Purpose: HIT occurs in up to 5% of patients exposed to heparin. HIT is characterized by a significant fall in platelet count and a hypercoagulable state. Diagnostic scoring tools exist to risk stratify patients prior to ordering laboratory assays, which are limited by either low sensitivity or delayed turnaround times. CS and MCS patients receive large heparin doses and have other significant reasons for thrombocytopenia. This project aims to assess the accuracy of diagnostic scoring tools used to predict HIT in CS and MCS patients.
 
Methodology: This single center, retrospective study included adult CS and MCS patients with a positive heparin-induced platelet antibody result from August 1, 2022, to December 31, 2024. Patients were identified via reporting tools within the Epic Hyperspace platform. Patient demographic information was collected. Patients were allocated based on whether they underwent cardiac surgery only (CS Group), MCS only (MCS Group), or required a combination of CS and MCS (CS-MCS Group). Types of CS and MCS, platelet count, serotonin release assay (SRA) result, duration of heparin therapy, duration of cardiopulmonary bypass (CPB), presence of additional medications implicated in causing thrombocytopenia, time to initiation of bivalirudin, and presence of thrombus were also collected. The primary was the negative predictive values of each of the diagnostic scoring tools (4T, m4T, and LLL scores) in the CS, MCS, and CS-MCS groups. Patients were stratified into risk-categories based upon their score from each of the diagnostic scoring tools. The NPV was then calculated from the true and false negatives.
 
Results: One hundred fifty-eight patients were screened and 92 met inclusion with 28 in the CS Group, 44 in the MCS Group, and 20 in the CS-MCS Group. The most common reasons for exclusion were duplicate patient identifiers, veno-venous extracorporeal membrane oxygenation support, and labs drawn prior to surgery or MCS initiation. The negative predictive value (NPV) for the 4T score in the CS group was 100% for low-risk and 64% for intermediate risk patients. For the m4T score, the NPV was 90% and 80% for the low and intermediate risk groups, respectively. The NPV for the LLL score in the CS group was 100% and 74% for the low and high-risk categories. For low-risk patients in the MCS Group, the NPV of the 4T and m4T scores were 97% and 92%.  For intermediate risk patients, the NPV of the 4T and m4T scores was 80% and 89%. There were no patients in the MCS Group who were classified as high risk by either score. The NPV for the 4T score in the CS-MCS group was 82%, and 63% for the low and intermediate risk categories.  As for the m4T, the NPV in the CS-MCS group was 100%, and 80% for the low and intermediate risk categories. The NPV for the LLL score in the CS-MCS group was 67% and 60% for the low and high-risk categories.
 
Conclusion: In this study, the m4T score had the highest NPV for those undergoing cardiac surgery procedures; however, for low risk stratified patients, all three tests were reliable in ruling out HIT. In the mechanical circulatory support group, both the 4T or m4T score had high NPVs. The m4T was more reliable in the joint cardiac surgery and mechanical circulatory support group.

Presentation Objective: Evaluate the accuracy of diagnostic scoring tools used to predict heparin-induced thrombocytopenia (HIT) in cardiac surgery (CS) and mechanical circulatory support (MCS) patients

Self-Assessment Question: Based on this study, which diagnostic scoring tool(s) is the best in CS, MCS, and CS + MCS patients to rule out HIT?
A. 4T score
B. m4T score
C. LLL score
D. All the above