American Board of Internal Medicine (ABIM) Certification Practice Exam

What points are associated with a high probability of heparin-induced thrombocytopenia according to the 4T scoring system?

1. 0 to 3 points

2. 4 to 5 points

3. 6 to 8 points

4. 9 to 10 points

The correct answer is: 6 to 8 points

In the context of heparin-induced thrombocytopenia (HIT), the 4T scoring system is a clinical tool used to estimate the probability of HIT based on four criteria: Thrombocytopenia, timing of platelet count fall, the presence of thrombosis, and other causes for thrombocytopenia. Scoring points in each category allows clinicians to stratify the risk of HIT. A score of 6 to 8 points indicates a high probability of HIT. This strong score reflects a significant drop in platelet count, the onset of thrombocytopenia within a relevant time frame after heparin exposure, evidence of new thrombosis, and a minimal likelihood of another cause for the thrombocytopenia. Such a score warrants immediate attention and further diagnostic evaluation, as it suggests that the patient is at considerable risk for developing serious complications from HIT. Lower scores, such as those ranging from 0 to 3, or the ranges of 4 to 5 and 9 to 10, reflect varying degrees of uncertainty regarding the diagnosis of HIT. These scores indicate low to moderate probabilities where the clinical picture may be less clear, suggesting other possible explanations for the thrombocytopenia or insufficient criteria to confirm HIT definitively.