Cost measurement in economic evaluations of health care - Whom to ask?

Purposes: The purposes of this study were 1) to investigate the feasibility of using providers' administrative systems for the assessment of healthcare utilization in economic evaluations performed alongside multicenter studies, 2) to assess the convergent validity of patients' and providers' reports of care, and 3) to investigate whether differences between providers' and patients' reports are related to age, gender, health, recall period, and volumes of care. Methods: Data were obtained as part of a cost-utility analysis alongside a multicenter clinical trial in patients with rectal cancer. For a sample of 179 patients from 49 hospitals, data on hospitalizations, outpatient visits, medications, and care products during the first year after treatment were obtained from the patients by questionnaire or diary. For all patients, hospitals were contacted for information on hospitalizations and outpatient visits. For a subsample of 94 patients, 86 pharmacists and 10 suppliers of stoma care products were contacted for information on medications and care products. Results: Response by providers of care was high, ranging from 84% to 100%. With respect to hospital days and outpatient visits, we found no significant differences between patients' and providers' reports. For medications and care products, agreement was lower, with providers reporting up to 2 times more product types and costs than patients. Providers failed to report 20% to 25% of all products, whereas patients failed to report 50% to 60% of all products. Conclusions: Patients' reports seem as valid as providers' reports for hospital days and outpatient visits. For medications and care products, we recommend the use of reports from providers of care, whenever feasible, because they much less underestimate volumes and costs than patients.