Physician conformity and patient adherence to ACE inhibitors and ARBs in patients with diabetes, with and without renal disease and hypertension, in a medicaid managed care organization

BACKGROUND: The American Diabetes Association (ADA) recommends using angiotensin-converting enzyme (ACE) inhibitors or angiotensin receptor blockers (ARBs) in patients with diabetes and comorbid hypertension or renal disease. OBJECTIVE: To examine the use of ACE inhibitors and ARBs in members of a Medicaid managed care organization (MCO) with diabetes and a diagnosis of hypertension and/or kidney disease to determine to what extent (1) physicians are conforming to the recommended course of treatment according to ADA guidelines published in 2002 and still current and (2) patients are adhering to their prescribed therapy. METHODS: Patients with diabetes were identified using medical claims from a Medicaid MCO in Maryland of approximately 118,000 members continuously enrolled during the study period. To be included in the cohort, members had to have at least 1 medical claim containing a diagnosis of diabetes mellitus from April 1, 2001, through March 31, 2002, using the International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) code of 250.xx. Additional medical claims during the same time period for hypertension, ICD-9-CM code 401.xx, and renal disease, ICD-9-CM codes for nephropathy (582.81 or 582.9), proteinuria (791.0), or diabetic nephropathy (250.40 or 250.42 for type 2 diabetes only), were used to categorize the cohort into 4 subgroups: diabetes and renal disease with hypertension, diabetes and renal disease without hypertension, diabetes and hypertension without renal disease, and diabetes without renal disease and without hypertension. Pharmacy claims for ACE inhibitors and ARBs were obtained from July 1, 2001, through June 30, 2002, and utilization was defined as the patient having at least 1 pharmacy claim for an ACE inhibitor or an ARB. Patient adherence with ACE inhibitor or ARB therapy was measured using medication possession ratio (MPR) and median gap between prescription refills. RESULTS: There were 1,698 patients, approximately 2.3% of the total continuously enrolled members, with 1 or more medical claims containing an ICD-9-CM code of 250.xx for diabetes mellitus. The average age was 48 +/- 13.2 years for the total sample, and nearly 70% of the patients were women (1,188 women and 510 men). Only 13% of the patients in the sample had medical claim evidence of any renal involvement, while 63% of the study patients had hypertension. A total of 915 patients (53.9%) had at least 1 pharmacy claim for an ACE inhibitor or an ARB, accounting for 7,934 unique pharmacy claims, an average of 8.7 pharmacy claims per patient. Patients with renal involvement and without hypertension (47%) were less likely to receive an ACE inhibitor or an ARB than patients with renal involvement and hypertension (85%) (P <0.001). Patients without renal involvement or hypertension (19%) were less likely to receive an ACE inhibitor or an ARB than patients with hypertension and no renal involvement (71%) (P <0.001). The MPR for all patients was 0.77 (+/- 0.26). MPR and median gap did not differ significantly by sex. However, we found a significant correlation between age and MPR (P <0.001). In this sample with an age range of 18 to 65 years, there was a positive relationship between patient age and adherence to ACE inhibitor or ARB therapy. CONCLUSIONS: Physicians' conformity is high when they prescribe an ACE inhibitor or ARB for patients with diabetes and hypertension but is lower than expected for patients with diabetes and renal disease but without hypertension. Older patients in this analysis of persons aged 18 to 65 years adhered more to their ACE inhibitor or ARB therapy.