A comparison of the 4Ts, HIT-Expert Probability (HEP), and Lill-Le Louët (LLL) scores in screening for heparin-induced thrombocytopenia in cardiac surgery patients

Cardiac surgery patients are at risk of developing heparin-induced thrombocytopenia (HIT); however, post-operative screening remains challenging. The 4Ts, HIT-Expert Probability (HEP), and Lill-Le Louët (LLL) scores are validated screening tools for HIT, yet literature in the post-operative cardiac setting is limited. This study compared the probability of the 4Ts, HEP, and LLL scores in detecting a positive serological diagnosis of HIT in cardiac surgery patients. Single-center, retrospective study. A single tertiary hospital. Patients ≥ 18 years old who underwent a cardiac surgery procedure and/or placement of a temporary mechanical support device with heparin exposure and had an enzyme-linked platelet-factor 4 immunosorbent assay (H-PF4) collected between July 1, 2017, and July 1, 2022. None A H-PF4 was collected on 282 patients: 30 had a positive H-PF4 and eight had a positive serotonin release assay (SRA). The median (IQR) scores for the 4Ts, HEP and LLL scores for patients with a positive versus negative SRA result were 5 (4 – 5) vs 4 (3 – 5) (P = 0.65), 4 (2 – 6) vs 3 (1 – 5) (P = 0.43), and 4 (3 – 4) vs 2 (1 – 2) (P < 0.001), respectively. The sensitivity of the 4Ts, HEP and LLL scores were 87.5%, 75.0% and 100%, respectively; and the specificities were 7.7%, 26.3%, and 39.6%, respectively. The LLL score may be the preferred HIT screening tool in adult cardiac surgery patients due to its high sensitivity and discriminatory potential between positive and negative HIT serological assays.