High rates of non-adherence to antihypertensive treatment revealed by high-performance liquid chromatography-tandem mass spectrometry (HP LC-MS/MS) urine analysis

Abstract

Objectives: Non-adherence to therapy is an important cause of suboptimal blood pressure control but few practical tools exist to accurately and routinely detect it. We used a simple urine-based assay to evaluate the prevalence of antihypertensive treatment non-adherence and its impact on blood pressure in a specialist hypertension centre.

Methods: 208 hypertensive patients (125 new referrals, 66 follow-up patients with inadequate blood pressure control and 17 renal denervation referrals) underwent assessment of antihypertensive drug intake using high-performance liquid chromatography-tandem mass spectrometry (HP LC-MS/MS) urine analysis at the time of clinical appointment. A total of 40 most commonly prescribed antihypertensive medications (or their metabolites) were screened for in spot urine samples.

Results: Overall, 25% of patients were totally or partially non-adherent to antihypertensive treatment (total non-adherence 10.1%, partial non-adherence 14.9%). The highest prevalence of partial and total non-adherence was among follow-up patients with inadequate blood pressure control (28.8%) and those referred for consideration of renal denervation (23.5%), respectively. There was a linear relationship between blood pressure and the numerical difference in detected/prescribed antihypertensive medications-every unit increase in this difference was associated with 3.0 (1.1) mm Hg, 3.1 (0.7) mm Hg and 1.9 (0.7) mm Hg increase in adjusted clinic systolic blood pressure, clinic diastolic blood pressure (DBP) and 24 h mean daytime DBP (p=0.0051, p=8.62 × 10(-6), p=0.0057), respectively.

Conclusions: Non-adherence to blood pressure lowering therapy is common, particularly in patients with suboptimal blood pressure control and those referred for renal denervation. HP LC-MS/MS urine analysis could be used to exclude non-adherence and better stratify further investigations and intervention.

Figure 1

Association between blood pressures and the numerical difference between detected and prescribed antihypertensive medications in all hypertensive patients. Point data are absolute blood pressure values recorded on either clinic or 24 h ambulatory monitoring, p value—adjusted (for age, sex, ethnicity and clinical category (new referrals, follow-up patients, referrals for renal denervation)) level of statistical significance for every unit change in blood pressure per unit change in the difference between detected and prescribed antihypertensive medications.

Figure 2

Association between blood pressures and the numerical ratio of detected and prescribed antihypertensive medications in all hypertensive patients. Point data are absolute blood pressure values recorded on either clinic or 24 h ambulatory monitoring, p value—adjusted (for age, sex, ethnicity and clinical category (new referrals, follow-up patients, referrals for renal denervation)) level of statistical significance for every unit change in blood pressure per unit change in the ratio of detected and prescribed antihypertensive medications.