CO-23: Routine urinary detection of antihypertensive drugs for estimation of adherence to treatment: a cross sectional study.

Background Adherence to antihypertensive treatment (AHT) is usually assessed by scales such as Morisky Medication Adherence Scale questionnaires (MMAS-4, MMAS-8) but objective urinary drug levels quantification by liquid chromatography mass spectrometry (LC-MS/MS) is now available. Our aim was to compare adherence assessed by LC-MS/MS or (MMAS-4/ MMAS-8) in patients with resistant hypertension (RH), compared to patients with controlled hypertension (CH). Methods RH cohort consisted in 82 outpatients with daytime ABPM u003e 135/85 mmHg after 4 weeks treatment with a standardised triple AHT: amlodipine + RAS blocker + thiazide. The CH cohort consisted in 91 patients followed in a routine care practice with controlled office BP ( Full adherence was defined by the presence of all prescribed drugs, partial adherence by the absence of at least one drug and finally full non-adherence by the absence of all antihypertensive drugs Results LC-MS/MS results: in the RH cohort, 63 patients (77%) were adherent, 11 (13%) were partly non-adherent and 8 (10%) were fully non-adherent. In the CH cohort, 86 (93%) were adherent, 5 (6%) were partly non-adherent, and 1 (1%) was fully non-adherent. Office SBP was significantly higher in non-adherent (partially or fully) than in fully adherent patients (median: 140 vs. 130 mmHg, respectively; p=0.01). Office DBP did not differ. According to LCMS-MS, the full adherence rate was significantly higher in CH cohort compared to RH (p=0.002). According to MMAS-8 available in 81 RH patients, 30 (37%) were fully adherent, and 51 (63%) were medium or low adherent. There was no concordance between LC-MS/MS and MMAS-8 in the same cohort (k=0.11, p=0.28). According to MMAS-4 available in 88 CH patients, 76 (86%) were fully adherent, and 12 (14%) were medium or low adherent and no significant difference in office SBP/DBP was observed between the two subgroups. There was no agreement between LCMS-MS and MMAS-4 (k=0.04, p=0.66). Conclusions In conclusion, measurement of urinary AHT by LC-MS/MS gives relevant information on adherence to treatment in patients attending an outpatient clinic. This information is not overlapping with questionnaires tests (MMAS). It confirms the role of objective non-adherence to treatment in resistance to treatment.