Good agreement between questionnaire and administrative databases for health care use and costs in patients with osteoarthritis

BACKGROUND Estimating costs is essential to the economic analysis of health care programs. Health care costs are often captured from administrative databases or by patient report. Administrative records only provide a partial representation of health care costs and have additional limitations. Patient-completed questionnaires may allow a broader representation of health care costs; however the validity and feasibility of such methods have not been firmly established. This study was conducted to assess the validity and feasibility of using a patient-completed questionnaire to capture health care use and costs for patients with osteoarthritis, and to compare the research costs of the data-capture methods. METHODS We designed a patient questionnaire and applied it in a clinical trial. We captured equivalent data from four administrative databases. We evaluated aspects of the questionnaire's validity using sensitivity and specificity, Lin's concordance correlation coefficient (ρ(c)), and Bland-Altman comparisons. RESULTS The questionnaire's response rate was 89%. Acceptable sensitivity and specificity levels were found for all types of health care use. The numbers of visits and the majority of medications reported by patients were in agreement with the database-derived estimates (ρ(c) > 0.40). Total cost estimates from the questionnaire agreed with those from the databases. Patient-reported co-payments agreed with administrative records with respect to GP office transactions, but not pharmaceutical co-payments. Research costs for the questionnaire-based method were less than one-third of the costs for the databases method. CONCLUSION A patient-completed questionnaire is feasible for capturing health care use and costs for patients with osteoarthritis, and data collected using it mostly agree with administrative databases. Caution should be exercised when applying unit costs and collecting co-payment data.