Cost-effectiveness results allow ambulatory monitoring to join NICE guidelines
Kate S. Lovibond, MSc, of the National Clinical Guideline Centre, Royal College of Physicians in London, and colleagues developed the model to test the cost-effectiveness of three strategies for diagnosing hypertension in patients who showed an initial blood pressure reading of greater than 140/90 mm Hg during a clinic visit.
The researchers noted that high blood pressure is a key risk factor for developing cardiovascular disease and is a leading cause of death worldwide. Accurate detection is challenging, though, because some patients have elevated blood pressure during doctor visits, and blood pressure varies throughout the day. Accurate screening potentially would lead to improved treatment and cost savings by identifying patients in need while eliminating those who don’t need treatment.
The three tested strategies were: further blood pressure measurement in the clinic over three monthly intervals; at home over one week; and with an ambulatory monitor worn over a 24-hour period. The model assumed a hypothetical primary care population of 40 years and older whose initial screening was 140/90 mm Hg or higher and included risk factors prevalent for that population. The model was run separately for 10 age-stratified and sex-stratified groups. Researchers applied a Markov model-based probabilistic cost-effectiveness analysis to determine lifetime costs, quality-adjusted life years and cost-effectiveness.
They found that ambulatory monitoring provided maximum cost benefits, with cost savings among all groups. Cost savings ranged from £56 ($92 U.S.) for 75-year-old men to £323 ($533 U.S.) for 40-year-old women. Patients older than 50 years saw quality-adjusted life year gains of 0.006 for women age 60 years and 0.022 for men age 70 years.
“Ambulatory monitoring allows better targeting of blood pressure treatment to those who will receive most benefit,” Richard J. McManus, MD, of Primary Clinical Sciences at the University of Birmingham in the U.K. and senior author, said in a statement. “It is already undertaken in some general practices and while implementation on a wide scale will need to be phased in to allow training and acquisition of new equipment, it is cost saving in the long term as well as more effective and so will be good for patients and doctors alike.”
The analyses were based on conservative assumptions, the authors noted, such as basing treatment costs on generic drugs when in reality usual care often includes a range of more expensive drugs. They pointed out additional benefits not captured in the model for those patients who would be misdiagnosed as hypertensive such as being exposed to unnecessary drug treatments, side-effects, prescription costs and potential social stigmas.
They argued that the use of recent population estimates made their model broadly applicable to the primary-care population but acknowledged that their assumptions could be a limitation. In an accompanying editorial, Thomas A. Gaziano, MD, of the cardiovascular division at Brigham and Women’s Hospital in Boston, recommended further sensitivity analyses and adjustments to assumptions that might demonstrate even more cost savings.
“One limitation of the model is that it was predicated on the assumption that treatment is a dichotomous decision based on blood pressure alone,” Gaziano wrote. “Since risk factors are not entirely independent, people with genuinely higher blood pressures would tend to also be at overall higher risk, probably strengthening the results, but this should be assessed in further analyses.”
NICE, which helped fund the study, annouced that based on the study results, it is recommending ambulatory monitoring as a best practice for patients with an elevated blood pressure reading at their initial clinic visit. The recommendation appears in hypertension guidelines jointly set by NICE and the British Society of Hypertension.