Spirometry, the St. George’s Respiratory Questionnaire, and other clinical measures as predictors of medical costs and COPD exacerbation events in a prospective cohort
AbstractPurpose:We conducted a prospective clinical cohort study of 300 established COPD patients randomly recruited from one managed care system to examine how well a battery of spirometry, exercise, and health status measures, including the St. Georges Respiratory Questionnaire (SGRQ), collected at baseline correlated with future healthcare costs and COPD exacerbations, and which were the most robust predictors of these outcomes in multivariate analyses.
Methods: All COPD patients treated over a 24-month period in the managed care system who met the utilization-based inclusion criteria were randomly recruited until 300 patients completed all clinical testing. Their healthcare utilization over the next 24 months was captured from administrative databases and used to develop multivariate models for healthcare costs and COPD exacerbations.
Results: The mean age of participants was 71 years, 62% were male, mean percent predicted FEV1(%pFEV1) was 60%, and median total healthcare costs in the follow-up period were $900 per month. Many factors correlated with increased total costs, but in linear regression models the parameters most predictive were age, Charlson comorbidity score, spirometry measures (%pFEV1or other measures, depending on the model), and the SGRQ Activity score. These same measures were also the most predictive of future exacerbations. Other measures such as the Borg score and treadmill time were significant in some models.
Conclusions: Four clinical measures (age, comorbidities, spirometry, and the SGRQ Activity score) are independent predictors of future healthcare costs and COPD exacerbations. Multidimensional scales for measuring COPD severity that are in development will need to account for these measures.