Functional Comorbidity Index in chronic rhinosinusitis

Background: The Functional Comorbidity Index is a promising tool to predict general health status and adjust for comorbidity confounding in outcomes studies of chronic conditions, but it has been tested as a predictor of general health status only in a sleep apnea cohort. We tested it in a chronic rhinosinusitis cohort with 2 objectives: (1) measure the association between the Functional Comorbidity Index (range, 0 to 18) and general health status (SF-36 Physical Component Score and Mental Component Score); and (2) test if the Functional Comorbidity Index is more strongly associated (a better predictor) than the well-known Charlson Comorbidity Index (range, 0 to 37) with these SF-36 outcome measures. Methods: In a cross-sectional study of chronic rhinosinusitis patients, we obtained scores for the Functional Comorbidity Index, Charlson Comorbidity Index, and the SF-36. We calculated Spearman correlations and adjusted coefficients of determination (R²) using multiple linear regression, adjusted for demographic covariates. Bootstrapping generated R² distributions for statistical comparison. Results: In the cohort (N = 97), the Functional Comorbidity Index scores (mean ± standard deviation: 2.2 ± 1.9) were more widely distributed than Charlson Comorbidity Index scores (0.6 ± 1.2). The Functional Comorbidity Index significantly correlated with the SF-36 Physical Component Score (-0.49, p < 0.001) and Mental Component Score (-0.37, p < 0.001). The Functional Comorbidity Index was a better predictor than the Charlson Comorbidity Index of SF-36 Physical Component Score (R² mean ± standard error: 0.21 ± 0.09 vs 0.15 ± 0.05; p < 0.001) and Mental Component Score (0.16 ± 0.10 vs 0.01 ± 0.06; p < 0.001). Conclusion: The Functional Comorbidity Index is a more robust predictor of general health status than the Charlson Comorbidity Index in chronic rhinosinusitis patients.