Incremental value of bilateral ankle-brachial index for ten-year heart and cerebrovascular mortality prediction: an exploratory temporal benchmark in NHANES

Bilateral ankle-brachial index added no incremental value for 10-year heart or cerebrovascular mortality prediction in NHANES 1999–2004, with AUROC and Brier changes near zero.

• Why it matters: ABI is linked to systemic vascular disease, but its added prognostic usefulness depends on the comparator, outcome, and how models are validated over time.
• What they did: Using survey-weighted NHANES adults ≥40 with bilateral ABI in [0.20, 2.50] and known 120-month status, models were trained on 1999–2002 and tested on 2003–2004. Incremental effects were assessed with 32-replicate Fay balanced repeated replication (15 design degrees of freedom), comparing flexible clinical regression versus flexible clinical plus ABI.
• The result: Evaluation AUROC was 0.834 with flexible clinical regression and 0.834 after adding ABI; the paired AUROC increment was -0.0007 (95% CI -0.0047 to 0.0032) and paired Brier difference was 0.0008 (95% CI -0.0003 to 0.0018). The hypothesis of improvement in both metrics was not supported, implying limited incremental predictive information in this temporal benchmark.

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