Reliability of women's histories of climacteric oestrogen treatment assessed by prescription forms.

A questionnaire study conducted in a cohort of women who had been prescribed oestrogen treatment for climacteric symptoms provided a unique opportunity to assess the concordance between their histories of oestrogen use and the exposure data derived from the prescription forms that had been collected for recruitment of the cohort. The questionnaire information, which was gathered within three years after the registration of prescription forms, was found to be highly concordant with the prescription data with respect to name of brand (85%), dosage (88%), treatment schedule--cyclic versus continuous--(88%), total duration of drug intake (months of treatment; correlation coefficient 0.98) and time of start of medication (correct month in 85%). A method for estimating the true exposure on the basis of prescription data--taking into account non-compliance and non-registered forms--was developed and found to be reproducible. It was concluded that information on climacteric oestrogen intake could be reliably obtained through a questionnaire within a period of less than three years after the exposure.