ArticlesCost-effectiveness of options for the diagnosis of high blood pressure in primary care: a modelling study
Introduction
High blood pressure is a key risk factor for the development of cardiovascular disease,1 and a major cause of morbidity and mortality worldwide.2 Hypertension is the most common reason for a primary-care consultation for a chronic disorder, and at least 25% of adults are hypertensive.3, 4
The diagnosis of hypertension has traditionally been based on several blood-pressure measurements made in the clinic, which are typically undertaken after a raised initial reading.5, 6, 7, 8, 9 Ambulatory blood-pressure monitoring better correlates with cardiovascular outcome10, 11, 12 than does clinic blood pressure, and it is used where there is uncertainty in diagnosis, resistance to treatment, irregular or diurnal variation, or concerns about variability and the so-called white-coat effect.13, 14, 15 Therefore, ambulatory monitoring is arguably the de facto reference standard for the diagnosis of hypertension. Moreover, recent analyses suggest that ambulatory monitoring is more accurate than both monitoring in the clinic and the home in defining the presence of hypertension and could therefore form part of the diagnostic pathway.16
Home blood-pressure monitoring, which provides many readings over several days, also better correlates with end-organ damage than measurement in the clinic.17, 18 Monitoring in the home seems a better prognostic indicator with respect to stroke and cardiovascular mortality than monitoring in the clinic and can detect the white-coat effect and masked hypertension.19, 20, 21 Although monitoring at home has a smaller evidence base, it might provide an appropriate alternative to ambulatory monitoring in terms of diagnosis, particularly in primary care where ambulatory monitoring is not always immediately available or when patients find it inconvenient or uncomfortable.
The use of out-of-office measurements in the initial screening of patients for hypertension is currently unsupported by evidence, hence it is probable that they would be undertaken after an raised initial reading in the clinic. Such a shift in practice would require substantial investment in new devices, especially in primary care, and it is unclear if this would be cost effective. Our aim was therefore to develop a model to assess the cost-effectiveness of three diagnostic strategies for hypertension after a raised initial clinic blood-pressure reading: further blood-pressure measurement in the clinic, at home, or with an ambulatory monitor.
Section snippets
Procedure
We did a cost-effectiveness analysis comparing blood-pressure monitoring in the clinic (measurements at monthly intervals over 3 months), in the home (measurements over a week), or ambulatory monitoring (measurements over 24 h). We expressed our findings in terms of costs, quality-adjusted life years (QALYs), and incremental costs per QALY gained. In the UK, an incremental cost-effectiveness ratio of less than £20 000–30 000 is generally thought cost effective by policy makers.22
In brief, we
Results
In our base-case analysis, ambulatory monitoring was the most cost-effective strategy for men and women of all ages. It was cost-saving in all groups and resulted in improved health outcomes for male and female age-groups older than 50 years (table 3). Consequently, ambulatory monitoring was the dominant strategy for men and women of most ages. For example, the base case results for a man aged 60 years showed that, compared with diagnosis by clinic monitoring, diagnosis by home monitoring
Discussion
Our findings show that ambulatory monitoring is cost effective compared with further monitoring in the clinic or home for confirming the diagnosis of hypertension in a population with suspected blood pressure greater than 140/90 mm Hg on the basis of a clinic screening measurement. Our conclusion is consistent across all age-stratified and sex-stratified subgroups we considered and is robust when assessed with a wide range of sensitivity analyses. The only exception was if home monitoring was
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