External Validation of the Walter Index for Posthospitalization Mortality Prediction in Older Adults.

Importance: The Walter Index is a widely used prognostic tool for assessing 12-month mortality risk among hospitalized older adults. Developed in the US in 2001, its accuracy in contemporary non-US contexts is unclear. Objective: To evaluate the external validity of the Walter Index in predicting posthospitalization mortality risk in Brazilian older adult inpatients. Design, Setting, and Participants: This prognostic study used data from a cohort of adults aged 70 years or older admitted to the geriatric unit of a university hospital in Brazil from January 1, 2009, to February 28, 2020. Participants underwent comprehensive geriatric assessments at admission, were reevaluated at discharge, and were subsequently followed up for 48 months. Data were analyzed from March to July 2024. Main Outcomes and Measures: The Walter Index, a score based on 6 risk factors (male sex, dependent activities of daily living at discharge, heart failure, cancer, high creatinine level, and low albumin level), was calculated to assess its predictive accuracy for 12-month mortality as well as 6-, 24-, and 48-month mortality. The study investigated whether incorporating delirium, frailty, or C-reactive protein level enhanced accuracy. Performance was assessed using discrimination, calibration, and clinical utility measures. Results: In total, 2780 participants (mean [SD] age, 81 [7] years; 1795 [65%] female) were included, with 89 (3%) lost to follow-up. The 12-month posthospitalization mortality rate was 23% (646 participants). Mortality was 7% (47 of 634) in the lowest-risk group (0-1 point), 17% (111 of 668) for 2 to 3 points, 25% (198 of 803) for 4 to 6 points, and 43% (290 of 675) in the highest-risk group (≥7 points). The index demonstrated an area under the receiver operating characteristic curve (AUC) of 0.714 (95% CI, 0.691-0.736) for predicting 12-month posthospitalization mortality (AUCs were 0.75 and 0.80 in the original derivation and validation cohorts, respectively). Comparable results were observed for mortality at 6 months (AUC, 0.726; 95% CI, 0.700-0.752), 24 months (AUC, 0.711; 95% CI, 0.691-0.730), and 48 months (AUC, 0.719; 95% CI, 0.700-0.738). Adding delirium modestly increased the index's discrimination (AUC, 0.723; 95% CI, 0.702-0.749); additionally including frailty and C-reactive protein level did not improve discrimination further (AUC, 0.723; 95% CI, 0.701-0.744). Conclusions and Relevance: In this prognostic study of hospitalized older adults in Brazil, the Walter Index showed similar discrimination in predicting postdischarge mortality as it did 2 decades ago in the US. These findings highlight the need for continuous validation and potential modification of established prognostic tools to improve their applicability across settings.