The ISTH Bleeding Assessment Tool and the risk of future bleeding

Background: The ISTH Bleeding Assessment Tool (ISTH-BAT) is a diagnostic tool used in subjects with suspected inherited bleeding disorders. Aim: To evaluate whether the ISTH-BAT, applied at first work-up in a tertiary-care center, predicts the risk of subsequent bleeding events. Methods: This was an observational cohort study including all consecutive subjects, of either sex and any age, referred between 2011 and 2015 because of a suspected bleeding disorder. The analysis was restricted to those with an ISTH-BAT score of >= 3. Incidence rates (IRs) of major bleeding (MB) and clinically relevant non-major bleeding (CRNMB) events were calculated as the number of events over accrued person-years. The main analysis was performed with Cox regression analysis, assessing an ISTH-BAT score of <= 5 versus a score of > 5, as well as the score as a continuous variable, and various covariates (sex, age, and presence/absence of a final diagnosis). Results: One hundred and thirty-six subjects had a median ISTH-BAT score of 4 (range 318). Eleven subjects (8.1%) had a bleeding event during follow-up (one MB event; 10 CRNMB events). The overall IR of bleeding events per 100 person-years was 3.7 (95% confidence interval [CI] 1.8-6.6). No difference was observed between subjects with an ISTH-BAT score of <= 5 and those with a score of > 5 (hazard ratio [HR] 1.2, 95% CI 0.3-4.6). The results were similar when the ISTH-BAT score was considered as a continuous variable (HR 1.1, 95% CI 0.9-1.4). The IR of bleeding was increased in individuals with a diagnosis of a hemostatic defect (IR of 7.5 per 100 person-years; HR 3.0, 95% CI 0.8-11.8). Conclusions: The ISTH-BAT does not identify patients at increased risk of future bleeding events.