Accuracy of indirect measures of medication compliance in hypertension.

The purpose of this study was to identify the most accurate indirect measure of medication compliance in primary hypertension through comparison with a recently developed direct measure of the antihypertensive agent, hydrochlorothiazide. A convenience sample of 40 subjects was seen by the investigator twice in an office setting and once in their homes. Data were collected by an interview schedule, blood pressure measurement, pill counts, urine analysis, and hospital record review. Patient interview was the most sensitive and accurate measure of compliance; this measure correctly classified 85% of patients as to compliant or noncompliant.