We aimed to evaluate the incremental prognostic value after incorporation of the ankle-brachial index (ABI) into the 10-year pool cohort equation (PCE) risk model in patients with multiple risk factors (MRFs). A total of 4332 MRFs patients were divided into 2 groups as ABI ≤.9 or >.9. The primary outcome was hard cardiovascular events (hCVE: including cardiovascular death, myocardial infarction, or ischemic stroke) over a median follow-up of 36 months. The Cox proportional hazards survival model, C-statistic, and net reclassification indices (NRI) were used. The occurrence of the primary outcome in the ABI ≤.9 group (3.7%) was significantly greater than in the ABI > .9 group (1.3%), P < .001. ABI is an independent predictor of hCVE in addition to the variables in the standard risk model (age, gender, and smoking status). ABI modestly improved the C-index when added to the PCE risk model (PCE .70 vs ABI+PCE .74). The addition of ABI to the PCE risk model did not significantly improve the classification of patients (NRI -.029; 95% CI: -.215 to .130). Despite ABI being one of the independent predictors of hCVE, integration of ABI into the PCE model did not improve the efficacy of risk reclassification in patients with MRFs.
Keywords: ankle-brachial index; atherosclerotic risk factors; pool cohort equation; risk reclassification; risk stratification.