Apparent treatment resistant hypertension in general practice: Quantifying the impact of white coat hypertension and non-adherence by ABPM and toxicological urine analysis.

Problem

To confirm treatment resistant hypertension (TRH), ambulatory blood pressure measurement (ABPM) must exclude white coat hypertension (WCH) and adherence to treatment should be examined. Previous general practice studies have not adequately considered the combined effect of these key features of pseudo-resistance. We aim to examine a cohort of general practice patients with apparent treatment resistant hypertension quantifying the impacts of white coat hypertension and non-adherence by the use of ABPM and toxicological urine analysis.

Approach

In fifteen university-research affiliated practices, 569 patients were identified through individual patient record review as having apparent treatment resistant hypertension and 453 invited to undergo ABPM and toxicological urine analysis-testing for 20 of the most common anti hypertensive drugs.

Findings

235 patients consented to provide urine for toxicological analysis-174 (74%) patients were fully adherent to anti-hypertension treatments, 56 (24%) patients partially adherent , and 5 (2%) patients non adherent. 210 patients also had 24 hour ABPM and 59 patients (28%) had WCH. Clinical predictors for non-adherence to therapy were examined including age, number and type of medications prescribed, and morbidity. Associations between ABPM and non-adherence were also explored.

Consequences

Evaluation of WCH via 24 hour ABPM is mandatory in diagnosing TRH. Adherence to medication- via anti-hypertensive drug urine toxicology analysis, suggests most patients take their prescribed medications, but for those who don’t, measures to improve adherence must be undertaken before further evaluation. Clinical predictors of those who are non-adherent may help physicians in the identification of these patients.