Ambulatory BP Monitoring Cheaper, Effective, and Gets Boost

Shelley Wood

August 24, 2011

August 23, 2011 (London, United Kingdom) — A long-time "reference standard" for tricky blood-pressure readings, ambulatory monitoring should now become the go-to test for diagnosing hypertension in all patients, authors of a new analysis say [1].

The study, now published online in the Lancet, was conducted jointly by independent researchers and an expert committee drafting an update to the UK's National Institute for Health and Clinical Excellence (NICE) Hypertension Guideline, officially launching on Wednesday [2]. The guidelines are the first in the world to formally recommend ambulatory blood-pressure monitoring (ABPM) as a "key priority" in diagnosing suspected hypertension, particularly if a clinic BP reading is 140/90 mm Hg or higher, according to the chair of the writing committee.

Works Better, Priced Right

The Lancet analysis, by Dr Kate Lovibond (National Clinical Guideline Centre, London, UK) et al, shows that using ABPM to diagnose hypertension is not only more effective than testing blood pressure at home or in the clinic, it also saved money in almost every patient group studied.

"Historically, ABPM been the reference standard when you've not been quite sure what to do," senior author on the Lancet analysis, Dr Richard J McManus (University of Birmingham, UK), told heartwire . "What we've realized from this and from a systematic review published in BMJ earlier this year [3] is that actually the reference standard is quite a lot better than clinic blood-pressure and to a lesser extent home blood-pressure monitoring at making a diagnosis."

Having established efficacy, investigators set out to see whether higher costs offset the value of ABPM--the devices are relatively expensive. "We were reasonably surprised when it showed just how cost-effective the ambulatory monitoring actually is," McManus said.

Study coauthor Dr Bryan Williams (University of Leicester, UK), who also chaired the update of the NICE hypertension guidelines, explained that the cost saving comes both from speeding up a diagnosis in someone who needs medication swiftly and from eliminating treatment in people who do not, in fact, have hypertension but have been misdiagnosed in the clinic or at home.

"ABPM is likely to eliminate from treatment up to 25% of newly presenting people with elevation of BP," he said. "If you remove the drug costs from those individuals, what we found was that modeling on 100 000 people in the UK that the ABPM would cost about ₤2.5 million to implement in the first year [which includes acquisition of equipment and training of personnel], but after that there was a progressive net gain in terms of cost. By year two it is cost neutral, and by year five this would save ₤10 million."

Williams continued: "So what we have here is a situation where we have a more effective way of diagnosing hypertension, it's better for patients, it eliminates unnecessary treatment in a significant number of patients, and at the same time it is potentially cost saving and at worst cost neutral. It's a no brainer to say: why aren't we doing this?"

Highest Savings in Older Patients

Lovibond, McManus, et al modeled cost-effectiveness in a hypothetical primary-care group undergoing 24-hour BP monitoring instead of clinic-based or home-based tests. They report that ABPM was the most cost-effective strategy across all age groups considered, and in both men in women. The lowest cost savings were in men over 75 years of age (an incremental saving of ₤56) compared with a diagnosis made with a clinic BP test, and highest among women aged 40 (₤323) per hypertension diagnosis.

ABPM also came out on top for improving health outcomes in men and women over age 50; in younger subjects, ABPM led to higher cost savings but smaller reductions in quality-adjusted life-years.

"The bottom line is that using ABPM as a diagnostic strategy for high BP is both more effective in terms of making a diagnosis and saving costs," McManus said.

There are no good data on just how commonly ABPM is used as the go-to test, he added. "We think that less than 5% of patients in the UK have ABPM as part of their diagnosis," he said. "There will be a few people for whom this won't be appropriate, particularly people with accelerated hypertension or people with very high BP who've had a stroke." In those patients, "you want to just get them on treatment, but in most people with suspected hypertension, particularly in the primary-care setting, we think this is the thing to do, and that's a big shift."

Other jurisdictions are increasingly looking to the UK's NICE model, because it balances both the evidence base and cost efficacy. Both McManus and Williams stressed that the Lancet paper, as well as the new NICE hypertension guidance, will have a ripple effect, particularly in places like the US, where ABPM is not always reimbursed. "I think this may get people internationally thinking about their diagnostic strategies as well," McManus said.

An editorial accompanying the study takes issue with some of the assumptions within Lovibond et al's analysis [4], saying further studies may be warranted to model specific scenarios, but if anything, writes Dr Thomas A Gaziano (Brigham and Women’s Hospital, Boston, MA), further studies might even strengthen the results.

NICE Hypertension Update Also Includes Drug Choices, Age Advice

The first NICE hypertension guideline was issued in 2004 and updated in June 2006. The new, simple, 16-page document lists "key priorities," provides a care "pathway," and encompasses different ways to measure and diagnose hypertension, assess risk and target-organ damage, use lifestyle and drug interventions, and educate patients.

Speaking with heartwire , Williams pointed to a number of other novel elements of this update.

For one, the update recommends the same antihypertensive drug treatment in people over aged 80 as in people aged 55 through 80, a change from previous guidance that urged caution in older subjects, out of concerns that adverse effects might offset benefits. A review of the evidence in older adults suggests there were reductions in stroke, hospitalizations for heart failure, and deaths and "no hint of any adverse offset" when a standard antihypertensive approach was applied, Williams said.

Second, in a recommendation that Williams predicts will be hotly debated in the UK, the NICE reviewers reexamined advice for subjects over age 55 and recommend the use of a calcium-channel blocker (CCB) as first-line therapy, with thiazidelike diuretics reserved for patients with edema, CCB intolerance, or evidence of heart failure or at high risk of heart failure.

And in a departure from previous recommendations, the new update recommends physicians use a thiazidelike diuretic, such as chlorthalidone or indapamide, in patients starting on or switching diuretics. These drugs should be used "in preference to" what is more commonly the first-line diuretic in the UK, bendroflumethiazide, says Williams, or the most common in the US, hydrochlorothiazide.

This will "prompt a lot of debate" not only in the UK, predicts Williams, but in the US as well.

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