A comparison of two methods of collecting economic data in primary care

BACKGROUND: There have been few attempts to assess alternative methods of collecting resource use data for economic evaluations. OBJECTIVE: This study aimed to compare two methods of collecting resource use data in primary care: GPs' case records and a self-complete postal questionnaire. METHODS: 303 primary care attenders were sent a postal survey, incorporating a questionnaire designed to collect service utilisation information for the previous six months. Data were also collected from GP case records. The reporting of GP visits between the two methods, and estimates of costs associated with those visits, were compared. RESULTS: There was good agreement between the number of GP visits recorded on GP case records (mean 3.03) and on the CSRI (mean 2.99) (concordance correlation coefficient = 0.756). In contrast, estimates of average costs of visits from CSRI data were higher and had greater variance compared to case record-based costs (54.63 pound sterling versus 42.37 pound sterling; P = 0.003). This may be explained by differences in average visit length (11.66 versus 9.36 minutes). CONCLUSIONS: This study shows good agreement between GP case records and a self-complete questionnaire for the reporting of GP visits. However, differences in costs associated with those visits arose due to differences in the method used for calculating length of visit.