Urine testing of patients with hypertension revealed that 25% were partially or totally nonadherent to treatment, researchers reported online April 3 in the journal Heart.
Furthermore, nonadherence was linearly related to increased systolic and diastolic blood pressures during clinic visits and 24-hour mean daytime diastolic blood pressure (P < .006 for all), reported Dr. Maciej Tomaszewski of the University of Leicester, England, and his associates.
Using a urine test available to commercial labs, the investigators tested 208 patients for 40 of the most common antihypertensive medications and their metabolites by performing high-performance liquid chromatography–tandem mass spectrometry of spot urine samples. Patients were either newly referred (n = 125), followed up for inadequately controlled blood pressure (66), or referred for renal denervation (17), the investigators reported (Heart 2014 April 3 [doi: 10.1136/heartjnl-2013-305063]).
Nonadherence was particularly common among patients whose hypertension was inadequately controlled (28.8%) or who were referred for renal denervation (23.5%), the investigators said. Without routine urine screening, nonadherent patients might receive or undergo unnecessary tests, procedures, or treatments for perceived nonresponse to treatment, said Dr. Tomaszewski, who is also with the National Institute for Health Research (NIHR) Leicester Biomedical Research Unit in Cardiovascular Disease, and his colleagues.
Larger, multicenter studies should directly estimate biochemical nonadherence in other populations and assess the cost-effectiveness of screening for nonadherence compared with the overall cost of managing resistant hypertension, the investigators said.
Dr. Tomaszewski and five of his associates reported receiving research and other support from the British Heart Foundation and the NIHR.