PATIENTS EXPERIENCE OF ADHERENCE TESTING IN UNCONTROLLED HYPERTENSION

Objective: Poor adherence to antihypertensive medications is a well-known cause of uncontrolled hypertension. Objective methods like directly observed therapy (DOT) or serum drug concentrations (s-conc.) of antihypertensive medication, has been documented to be useful in diagnosing non-adherence in clinical studies. Unannounced measurements of s-conc. is still not routine in clinical practice, partly due to fear for interrupted physician-patient relationship. We investigated the prevalence of non-adherence in patients with apparent resistant hypertension referred to our outpatient clinic by comparing s-conc. and DOT. The aim of this study is to investigate how the patients experienced being tested for non-adherence by both methods.Design and method: 20 patients referred to 24-hour ambulatory blood pressure measurement (ABPM) were included. All had uncontrolled blood pressure (office SBP >140 mmHg, office DBT >90) despite the use of at least three antihypertensive drugs at referral point. ABPM was performed at baseline and repeated after 3-4 weeks, the second measurement succeeding DOT. S- conc. of antihypertensive drugs by ultra-high-performance-liquid-chromatography tandem mass spectrometry were measured at baseline and 24 hours after DOT. Patients were informed of the measurement immediately before the venepuncture. Patients with s-conc. below predefined reference levels of one or more drugs were considered non-adherent. Patients evaluated how they experienced the DOT and S- conc. measurements by a visual analogue scale (VAS score) from 0 –10, were 0 was “not unpleasant at all” and 10 was “very unpleasant”. Results: 9 of 20 (45%) patients were defined as non-adherent at the first visit based on serum drug concentrations reference values of antihypertensive drugs. The non-adherent patients had a decrease in systolic ABPM of 12±13mmHg after DOT, while the adherent patients had no difference in systolic ABPM. All patients completed the VAS questionnaire, and one patient (adherent) found s-conc. measurements uncomfortable, rated 5 on the VAS scale. Conclusions: There is a high prevalence of non-adherence to antihypertensive drugs in patients with apparent resistant HT referred to our outpatient clinic, identified both by s-conc. and by DOT. Both methods seem to be well tolerated by the patients, only one patient found s-conc. unpleasant.