Measuring adherence to therapy in apparent treatment-resistant hypertension: a feasibility study in Irish primary care

Peter Hayes; Monica Casey; Liam G Glynn; Gerard J Molloy; Hannah Durand; Eoin O'Brien; Eamon Dolan; Kishor Das; John Newell; David Finn; Brendan Harhen; Ann Conneely; Andrew W Murphy

doi:10.3399/bjgp19X705077

Measuring adherence to therapy in apparent treatment-resistant hypertension: a feasibility study in Irish primary care

Br J Gen Pract. 2019 Aug 29;69(686):e621-e628. doi: 10.3399/bjgp19X705077. Print 2019 Sep.

Authors

Peter Hayes¹, Monica Casey², Liam G Glynn², Gerard J Molloy³, Hannah Durand³, Eoin O'Brien⁴, Eamon Dolan⁵, Kishor Das⁶, John Newell⁶, David Finn⁷, Brendan Harhen⁷, Ann Conneely⁷, Andrew W Murphy⁸

Affiliations

¹ Graduate Entry Medical School, University of Limerick, Limerick; Discipline of General Practice, National University of Ireland (NUI) Galway, Galway, Ireland.
² Graduate Entry Medical School, University of Limerick, Limerick, Ireland.
³ School of Psychology.
⁴ Conway Institute, University College Dublin, Dublin, Ireland.
⁵ Department of Medicine for the Elderly, Connolly Hospital, Blanchardstown, Dublin, Ireland.
⁶ School of Mathematics, Statistics and Applied Mathematics.
⁷ Discipline of Pharmacology and Therapeutics, School of Medicine, NUI Galway, Galway. Ireland.
⁸ Health Research Board Primary Care Clinical Trials Network; Discipline of General Practice, NUI Galway, Galway, Ireland.

Abstract

Background: Apparent treatment-resistant hypertension (aTRH) is defined as uncontrolled blood pressure (BP) in patients taking three or more antihypertensive medications. Some patients will have true treatment-resistant hypertension, some undiagnosed secondary hypertension, while others have pseudo-resistance. Pseudo-resistance occurs when non-adherence to medication, white-coat hypertension (WCH), lifestyle, and inadequate drug dosing are responsible for the poorly controlled BP.

Aim: To examine the feasibility of establishing non-adherence to medication, for the first time in primary care, using mass spectrometry urine analysis. Operationalisation would be established by at least 50% of patients participating and 95% of samples being suitable for analysis. Clinical importance would be confirmed by >10% of patients being non-adherent.

Design and setting: Eligible patients with aTRH (n = 453) in 15 university research-affiliated Irish general practices were invited to participate.

Method: Participants underwent mass spectrometry urine analysis to test adherence and ambulatory BP monitoring (ABPM) to examine WCH.

Results: Of the eligible patients invited, 52% (n = 235) participated. All 235 urine samples (100%) were suitable for analysis: 174 (74%) patients were fully adherent, 56 (24%) partially adherent, and five (2%) fully non-adherent to therapy. A total of 206 patients also had ABPM, and in total 92 (45%) were categorised as pseudo-resistant. No significant associations were found between adherence status and patient characteristics or drug class.

Conclusion: In patients with aTRH, the authors have established that it is feasible to examine non-adherence to medications using mass spectrometry urine analysis. One in four patients were found to be partially or fully non-adherent. Further research on how to incorporate this approach into individual patient consultations and its associated cost-effectiveness is now appropriate.

Keywords: hypertension; primary care; pseudo-resistance; treatment adherence; urinalysis.

MeSH terms

Aged
Aged, 80 and over
Antihypertensive Agents / therapeutic use*
Antihypertensive Agents / urine
Blood Pressure Monitoring, Ambulatory*
Feasibility Studies
Female
Humans
Hypertension / drug therapy*
Hypertension / physiopathology
Ireland
Male
Mass Spectrometry
Medication Adherence*
Middle Aged
Primary Health Care*
Urinalysis
White Coat Hypertension / diagnosis*

Substances

Antihypertensive Agents