Detecting non-adherence by urine analysis in patients with uncontrolled hypertension: rates, reasons and reactions

Abstract

Poor adherence with pharmacotherapy is well recognised as one of the main barriers to achieving satisfactory blood pressure control, although accurately measuring patient adherence has historically been very challenging. Urine analysis by high-performance liquid chromatography-tandem mass spectrometry has recently become routinely available as a method of screening for non-adherence. In addition to measuring rates of adherence in hypertensive patients, this study aimed to investigate the reasons for non-adherence given by patients and how patients react when they are informed of their results. This was a retrospective observational study looking at results from the routine use of this assay in a specialist hypertension clinic in Birmingham, UK, in patients with uncontrolled hypertension and those under consideration for renal denervation. Out of the 131 patients analysed, only 67 (51%) were taking all their medications as prescribed. Forty-three patients (33%) were taking some of their medications, whilst 21 patients (16%) were completely non-adherent. The most common reasons cited for non-adherence were adverse effects of medication and forgetfulness. Adherence rates for thiazide/thiazide-like diuretics and spironolactone were lower than for other classes of antihypertensive drug. Despite the objective nature and high sensitivity of the test, 36% of non-adherent patients disputed the results. A minority of patients did not attend follow-up. Further research investigating the implications of a 'non-adherence' result on the patient-clinician relationship is required.

Biochemical Screening for Nonadherence Is Associated With Blood Pressure Reduction and Improvement in Adherence

“…This form of nonintentional nonadherence to antihypertensive therapy was also demonstrated as one of the main barriers to adherence in other studies. 41 , 42 Our study is not immune from the so-called toothbrush effect 43 —patients may have taken their medications just before their clinic appointment and thus influence their clinic BP measurement. To this end, the availability of 24-hour ambulatory BP monitoring data showing the same direction of BP changes is reassuring because this investigation was conducted at a different time point from the clinic appointment.…”

Diagnosis and management of hypertension in primary care

“…Studies in this setting using high-performance liquid chromatography-mass spectrometry (HPLC-MS/MS) of random urine samples have shown that up to half of patients were totally or partially non-adherent to antihypertensive treatment. 26 Healthcare professionals should therefore have a high index of suspicion for non-adherence in patients with poor BP control despite being prescribed multiple antihypertensives. A non-judgemental and non-confrontational approach to the issue is recommended when discussing this with the patient, in order to avoid a breakdown in the patient-clinician relationship.…”

“…Strategies to improve adherence should be tailored to the individual because patients have different reasons for nonadherence. Intolerance to medication is a common factor 26 and patients with multiple drug intolerance should be referred to a hypertension specialist (see Table 2).…”

Perioperative use of renin-angiotensin system inhibitors and outcomes in patients undergoing cardiac surgery

“…Third, we lacked data on the dose and adherence of RASi in this cohort of patients. The reported rates of patient RASi adherence for cardiovascular protection are high, range from 68 to 92% in the literature 35,36 . Finally, both CABG and valve surgery patients were included in this study since RASi have been shown to be beneficial in both groups of patients 1,2,6–10,12,18,19 .…”