Objective: This study was conducted to evaluate the relationship between medication compliance and blood pressure (BP) control among members of 13 managed care organizations with essential hypertension (HTN) who received antihypertensive monotherapy for at least 3 pharmacy claims prior to the blood pressure measurement.
Methods: This was a retrospective review of medical and pharmacy claims over a 4-year period (1999-2002) from 13 U.S. health plans. Data were collected by trained health professionals from randomly selected patient medical records per Health Plan Employer Data and Information Set (HEDIS) technical specifications. Patients were selected if they (1) had received monotherapy or fixed-dose combination therapy (administered in one tablet or capsule) during the time BP was measured (thus those with no BP drug therapy were excluded); (2) had received 3 or more antihypertensive pharmacy claims for the antihypertensive drug therapy prior to BP measurement; and (3) had one or more antihypertensive pharmacy claims after BP was measured. Control of BP was defined according to guidelines of the Sixth Report of the Joint National Committee (JNC 6) on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (<140/90 mm Hg, or <130/85 mm Hg for patients with diabetes). Medication adherence was measured using the medication possession ratio (MPR), and MPR was used to classify patients into 3 adherence levels: high (80%-100%), medium (50%-79%), and low (<50%). The relationship between medication adherence and BP control was assessed using a logistic regression model.
Results: There were 1,017,181 patients with a diagnosis of HTN in medical claims data from which 10,734 (10.6%) were randomly selected for chart review. There were 1,032 patients (9.6%) in the sample who had a diagnosis of HTN but who were excluded because they had no HTN drug therapy. Of the total 9,894 patients (92.2%) who were excluded from the sample, 3,029 patients (28.2%) met all other inclusion criteria but were receiving more than one HTN drug. Of the 840 patients on HTN monotherapy, the mean age was 59 12.2 years; 422 (50%) were women, 16% had diabetes, and 43% had dyslipidemia. The monotherapy HTN drug was an angiotensin-converting enzyme inhibitor (27% of patients), calcium channel blocker (22%), beta-blocker (20%), or diuretic (11%). Of the 840 patients, 629 (74.8%) were determined to have high medication adherence, 165 (19.6%) had medium adherence, and 46 (5.5%) had low adherence. Approximately 270 (43%) of high adherence patients achieved BP control compared with 56 (34%) and 15 (33%) patients with medium and low adherence, respectively. High-adherence patients were 45% more likely to achieve BP control than those with medium or low compliance after controlling for age, gender, and comorbidities (odds ratio=1.45; P =0.026).
Conclusion: These results demonstrate that 75% of these health plan members with a diagnosis of essential HTN who were selected for receipt of at least 4 pharmacy claims for HTN monotherapy exhibited high medication adherence. However, only 43% of high-adherence patients attained their target (JNC 6) blood pressure goal compared with 33% to 34% of patients with medium or low adherence to antihypertensive monotherapy.