Self-reports of health-care utilization: diary or questionnaire?

OBJECTIVES: The feasibility and convergent validity of a cost diary and a cost questionnaire was investigated.
METHODS: Data were obtained as part of a cost-utility analysis alongside a multicenter clinical trial in patients with resectable rectal cancer. A sample of 107 patients from 30 hospitals was asked to keep a weekly diary during the first 3 months after surgery, and a monthly diary from 3 to 12 months after surgery. A second sample of seventy-two patients from twenty-eight hospitals in the trial received a questionnaire at 3, 6, and 12 months after surgery, referring to the previous 3 or 6 months. Format and items of the questions were similar and included a wide range of medical and nonmedical items and costs after hospitalization for surgery.
RESULTS: Small differences were found with respect to nonresponse (range, 79 to 86 percent) and missing questions (range, 1 to 6 percent between the diary and questionnaire). For most estimates of volumes of care and of costs, the diary and questionnaire did not differ significantly. Total 3-month nonhospital costs were 1,860 Euros, 1,280 Euros, and 1,050 Euros in the diary sample and 1,860 Euros, 1,090 Euros, and 840 Euros in the questionnaire sample at 3, 6, and 12 months after surgery, respectively (p = .50). However, with respect to open questions, the diary sample tended to report significantly more care.
CONCLUSIONS: For the assessment of health-care utilization in economic evaluations alongside clinical trials, a cost questionnaire with structured closed questions may replace a cost diary for recall periods up to 6 months.