No relationship between HF medication adherence, Part D spending

Researchers have found significant regional variation in Medicare Part D spending for heart failure (HF) medications, as well as significant regional variation in medication adherence among HF patients. But they have not found an association between the two. The findings appeared online Feb. 11 as a research letter in the JAMA Internal Medicine.

Yuting Zhang, PhD, of the Graduate School of Public Health at the University of Pittsburgh, and colleagues examined Medicare Part D data from 2005 to 2007 to find patients with a diagnosis of HF and prescriptions for at least one of these HF drug regimens: beta-blockers; angiotensin converting enzyme inhibitors or angiotensin receptor antagonists; or diuretics. They identified 178,102 such Medicare Part D beneficiaries and, using the patients’ residential zip codes, assigned them to 306 Dartmouth hospital referral regions.

The researchers measured adherence by the medication possession ratio (MPR), defined as the total number of pills the patient had over the total number of pills the patient was prescribed. They also reviewed gross spending on pharmaceuticals, the number of monthly prescriptions filled, and the intensity of treatment, which they defined as the proportion of patients who received all three classes of drugs among those patients who were prescribed at least one class of HF medication.

They found an average of 52 percent of patients had good HF medication adherence (MRP greater than or equal to 0.8), but there was wide geographic variability in adherence, from a low of 36 percent to a high of 71 percent. There also was wide variation in treatment intensity among HRRs, and in drug spending. But “the area at the 90th percentile of drug spending had per-person drug spending that was 31 percent higher than the area at the 10th percentile of drug spending but had only 15 percent higher number of prescriptions.” The researchers attributed the spending variance to different mixes of drugs in different hospital referral regions.

The researchers found no association between higher drug spending and better medication adherence. “This suggests that areas with higher drug spending are not necessarily caring for patients with HF more efficiently,” they wrote.

“Areas with better adherence can provide a useful benchmark for what is achievable, and system-level quality metrics that incorporate adherence, rather than focusing solely on drug spending, could promote more efficient use of resources,” they concluded.     

Zhang et al noted several limitations of their study, including the fact that MPR cannot capture emerging contraindications, untaken pills or changes in physician orders. The researchers also acknowledged that they could not adjust for regional medication preferences.