One in 4 patients were partially or totally noncompliance with their anti-hypertensive regimens, and wound up with either suboptimal blood pressure control a referral for renal denervation as a result, a study found.
Researchers in the Leicester, England noted this noncompliance rate while testing a urine-based assay that could detect when patients aren’t taking their medications as prescribed. They used high performance liquid chromatography-tandem mass spectrometry urine analysis on 208 hypertensive patients (125 new referrals, 66 follow-up patients with inadequate blood pressure control and 17 renal denervation referrals) to look for 40 of the most commonly prescribed antihypertensive medications or their metabolites in spot urine samples.
Results appeared online April 2 at Heart.
Total non-adherence was 10.1% and partial non-adherence was 14.9%, the study found. The highest prevalence of partial nonadherence was 28.8% for patients with inadequate blood pressure control and 23.5% for those referred for consideration of renal denervation.
Nonadherent patients took an average of 1 fewer drug than what they had been prescribed. There was a linear relationship between the numerical difference between the detected vs. prescribed antihypertensive medications and blood pressure. For every 1 unit increase in the difference between prescribed vs. detected medications, there was a 3.0 (1.1) mm Hg in adjusted clinic systolic blood pressure (P=0.0051), a 3.1 (0.7) mm Hg in clinic diastolic blood pressure (P=8.62×10−6), and a 1.9 (0.7) mm Hg increase in 24 hour mean daytime diastolic blood pressure. (P=0.0057).
“A majority of these patients in any secondary/tertiary care center would routinely undergo many additional tests and procedures in search of the explanation for their apparent unresponsiveness to standard therapy prescribed by primary care,” the authors wrote. “Our data suggest that in 20% of such patients, these investigations (along with follow-up appointments and exposure to unnecessary additional treatment) could be potentially avoided if [spectrometry] urine analysis was used as a routine screening for non-adherence.”
An editorial noted that a mass spectrometry assay for all commonly used antihypertensive drugs should rapidly transform practice.
“That most patients do not take all their drugs all the time was probably predictable,” the editorial stated. “But that 23% of those referred for renal denervation have no detectable drug in their urine was a shock. These patients may be the extremes, both among those who are non-adherent and among those referred for renal denervation. But they account for a disproportionate and wasteful use of resource in their management. … with renal denervation appearing unlikely now to feature in clinical practice, the relevance of the Leicester findings should be generalized to any patient apparently uncontrolled despite multiple drugs.”