Whitney Comorbidity Index to monitor health status for adults with cerebral palsy: validation and thresholds to assist clinical decision making.

AIM To validate the Whitney Comorbidity Index (WCI), which was recently developed to monitor disease status for adults with cerebral palsy (CP), and to identify WCI scores associated with an increased mortality risk using a representative sample of adults with CP. METHOD Data from 2016 to 2018 were used from a random 20% sample from the fee-for-service Medicare database for this retrospective cohort study. The WCI was examined as unweighted (WCIunw ) and weighted (WCIw ) among adults at least 18 years old with CP. Cox regression models were developed with mortality as the outcome after adjusting for demographics. A concordance statistic (C-statistic) of at least 0.70 was considered as showing sufficient validity. The hazard ratio of mortality for each WCI score was estimated. Secondary analyses were performed for subgroups with co-occurring epilepsy and/or intellectual disabilities. RESULTS For the entire group (n=16 728) and subgroups, the WCI showed sufficient validity (C-statistic 0.73-0.81). For the entire group, the mortality rate was elevated for a score of 1 compared with 0 from the WCIunw (hazard ratio 3.06; 95% confidence interval [CI] 1.52-6.17) and WCIw (hazard ratio 4.08; 95% CI 1.69-9.85), and became larger with each WCI score. Results were similar for the subgroups. INTERPRETATION The WCI is a valid marker for health/disease status for adults with CP. Several WCI score thresholds were identified to assist in clinical decision making for preventive medicine and intervention implementation.