Agreement between self-reported antihypertensive drug use and pharmacy records in a population-based study in The Netherlands

From 1987 to 1991, over 36,000 men and women aged 20-59 years have been exa mined in the Monitoring Project on Cardiovascular Disease Risk Factors in T he Netherlands. Classification of the treatment status of hypertensives in this population-based study was based on self-administered questionnaires. In order to assess the accuracy of self-reported antihypertensive drug use we compared the questionnaire information with computerized pharmacy record s from a sample of 372 hypertensive subjects. Most antihypertensive drugs t hat were mentioned in the questionnaire were present in the pharmacy medica tion history (93%). However, this percentage was less (76%) when a comparis on was made with the calculated duration of use based on the number of unit s prescribed and the directions for use in the pharmacy records. About 94% of the hypertensive subjects who were using an antihypertensive drug accord ing to the pharmacy records, also mentioned at least one antihypertensive d rug in the questionnaire. Agreement between self-reported antihypertensive drug use and pharmacy records was consistently high for all classes of anti hypertensive drugs. Among 321 (86%) subjects, the number and types of self- reported antihypertensive drugs were exactly the same as in the pharmacy re cords. In conclusion, the agreement between self-reported antihypertensive drug use and pharmacy records was high, and the self-reported questionnaire information on antihypertensive drug use can be reliably used for the clas sification of treatment status of hypertensive subjects in this population- based study.