CONTEXT: The Patient-Reported Outcome Mortality Prediction Tool (PROMPT) estimates six-month mortality risk in elderly patients with declining health, but its external validity has not been established.

OBJECTIVES: To prospectively validate the PROMPT in an independent patient cohort and explore its clinical utility.

METHODS: The study cohort comprised a diverse sample of 467 patients aged 65 years and older. Model calibration and discrimination were assessed on the original PROMPT and in two updated models. Clinical utility of the final updated PROMPT was examined using decision curve analysis.

RESULTS: The validation cohort had a lower six-month mortality rate than the derivation cohort (6.9% vs. 15.0%). Discrimination was virtually unchanged (area under the curve 0.73 compared with 0.75), but calibration was suboptimal (P < 0.05 for the Hosmer-Lemeshow test). The PROMPT, therefore, was updated with a new intercept and slope parameter that significantly improved calibration (Hosmer-Lemeshow statistic of 0.66). Specificity of the PROMPT was high (92% and 97%, respectively, at the 10% and 20% mortality risk thresholds), although sensitivity was modest (53% and 44% at the corresponding thresholds), consistent with diagnostic performance in the derivation sample. Decision curve analysis demonstrated greater net benefit of the updated PROMPT than "treat all" or "treat none" strategies, especially at low to moderate risk thresholds.

CONCLUSION: The PROMPT demonstrated good discrimination but poor calibration in an independent heterogeneous clinical population. Model updating improved calibration and diagnostic performance and decision curve analysis demonstrated potential clinical utility of the PROMPT for initiating advance care planning rather than hospice referrals.