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Patients may overstate their use of antihypertensive medication

Patients with high blood pressure (hypertension) markedly overstate how much antihypertensive medication they take, according to a recent study that was supported in part by the Agency for Healthcare Research and Quality (T32 HS00020). Therefore, clinicians should be cautious when relying solely on patient reports of medication compliance to evaluate the effectiveness of a given regimen. Inaccurate reports of compliance may prompt doctors to diagnose a patient's hypertension as nonresponsive to current medication, needlessly switch therapies, or expose patients to potentially toxic antihypertensive regimens, according to Philip S. Wang, M.D., Dr.P.H., of Brigham and Women's Hospital in Boston.

Dr. Wang and his colleagues conducted a telephone survey of 200 hypertensive patients (mostly of whom were white and older than 55) treated with a single antihypertensive agent either in a large HMO or a Veterans Affairs medical center. Patients were asked about how often they missed taking their antihypertensive medication, and their responses were compared with records of filled prescriptions. The researchers found very poor agreement between self-reported compliance and days actually covered by filled prescriptions. There was also very poor agreement between a measure of self-reported compliance (ever vs. never missing a dose) and categories of actual compliance defined by filled prescriptions (80 percent vs. more than 80 percent of days covered).

Patients who saw their doctors more frequently (perhaps a marker for a closer doctor-patient relationship) were much more likely to admit to imperfect compliance. Patients may overestimate compliance for several reasons. Some may never have received clear instructions from their physicians or fully understood the instructions they were given. Desire to please the doctor may also be a factor.

See "How well do patients report noncompliance with antihypertensive medications? A comparison of self-report versus filled prescriptions," by Dr. Wang, Joshua S. Benner, Pharm.D., M.S., Robert J. Glynn, Sc.D., Ph.D., and others, in the January 2004 Pharmacoepidemiology and Drug Safety 13, pp. 11-19.

Editor's Note: Another AHRQ-supported study on a related topic found that a computer-based physician order-entry system failed to improve antihypertensive treatment compliance or outcomes of patients with uncomplicated hypertension. For more details, see Murray, M.D., Harris, L.E., Overhage, M., and others (2004). "Failure of computerized treatment suggestions to improve health outcomes of outpatients with uncomplicated hypertension: Results of a randomized controlled trial." (AHRQ grant HS07763). Pharmacotherapy 24(3), pp. 324-337.

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