Prognostic comparison between GMFCS and WCI for 5-year risks of 22 relevant health outcomes for adults with cerebral palsy: Expanding the methodological menu for prognostic model research.

Background: The gross motor function classification system (GMFCS) is a well-established measurement of function specific to cerebral palsy (CP) and likely offers prognostic ability for disease trajectories. However, other emerging measurements may be more directly aligned with assessing disease risk for adults with CP, such as the Whitney Comorbidity Index (WCI).

Objective: To expand the methodological menu for prognostic model research, this study assessed whether GMFCS or WCI served as a better prognostic factor of 5-year risks of mortality and 21 relevant morbidity outcomes among adults with CP.

Methods: This retrospective cohort study used medical records from 01/01/2012-06/01/2024 from adults ≥18 years old with CP. A 1-year baseline ascertained the WCI score. Logistic regression estimated and compared the c-statistic of each outcome between: (1) base model (age, sex, race, smoking status, insurance, year of start date) + GMFCS and (2) base model + WCI. Multiple imputation was used for missing GMFCS data to address sample selection bias.

Results: In the complete case analysis with no missing GMFCS data (n = 923), 14 of 21 morbidity outcomes were similarly predicted by base + GMFCS and base + WCI models and 7 were predicted better by base + WCI model, while the mortality outcome was predicted better by base + GMFCS. Using the full cohort after multiple imputation (n = 2601), 18 morbidity outcomes were similarly predicted by both models and 3 were predicted better by base + WCI model, while the mortality outcome was predicted better by base + GMFCS.

Conclusions: This study suggests that while GMFCS was superior for mortality prediction, the WCI had similar-to-superior prediction for most morbidity outcomes.