If you’ve been prescribed a blood pressure medication based on a single high number at your doctor’s office, you may want to ask if you really need it. That blood pressure reading might be misleading, according to an influential panel of government experts.
In its draft recommendation, the U.S. Preventive Services Task Force has concluded that a hypertension diagnosis made at a clinic or doctor’s office should be verified by a series of readings taken as you go about your day. Here’s why ambulatory monitoring — done away from a medical setting — gives a truer picture of your blood pressure.
White Coat Hypertension: It’s Real
“But it was fine when I took it at home,” is what office nurses often hear as they unwrap the blood pressure cuff from a patient’s arm. “White-coat hypertension” is no myth, says Mary Bauman, a physician on staff with Intergris Family Care Central in Oklahoma City. “If you run up the stairs to the doctor’s office, if you’re in traffic and you’re trying to get there, your blood pressure may be elevated,” Bauman says. “Everybody’s blood pressure goes up at certain times. It’s supposed to.”
High readings during checkups may not match follow-up home readings that turn out to be fine. “No doctor wants to change people’s medication based on one reading in the office,” Bauman says. Masked hypertension — where blood pressure is always lower in the doctor’s official — is the opposite effect that occurs for some patients, she notes. Taking a second or third reading during the visit may help “somewhat,” she says.
“What we’re really interested in — is your blood pressure elevated most of the time?” Bauman says. “That’s chronic wear and tear on your blood vessels, and it promotes atherosclerosis and increases your risk of heart attack and stroke.”
Three types of measurements — office-based, ambulatory and home monitoring — were compared in a newly updated review of studies commissioned by the USPSTF.
“What we found is that office-based measurements identified more hypertensive patients that were then not confirmed by ambulatory monitoring,” says Maggie Piper, review author and a senior investigator at the Kaiser Permanente Center for Health Research in Portland, Oregon.
This finding “varied considerably across studies,” Piper says. “They agreed better in the offices where more measurements were taken. When there was just one measurement, the agreement between the two measurements was not as good.” The accuracy gap was smaller among older patients, or at blood pressure levels well above normal thresholds.
With ambulatory monitor monitoring, “your provider is setting you up with a piece of equipment that you take home for about 24 hours,” Piper explains. “It consists of an arm cuff that you wear for the whole 24 hours.” A small, connected computerized pack that hooks to your belt stores the readings from the cuff, which is programmed to inflate every 20 to 30 minutes during the day, and every 30 to 60 minutes at night. “During that time you’ll also keep a diary of your activities: ‘I ate at this time, I exercised at this time,” she says. “Your major activities.”
That gives health providers a lot more to look at, Piper continues: “In comparison to the office measurement of one to three measurements, you have many measurements, over time, outside of the office setting.”
Home blood pressure monitoring is what you do on your own, with an instrument you can buy over the counter. (Those that measure blood pressure at the upper arm are more accurate than others using the wrist or finger, Piper says.) With home monitoring, “you only get as many measurements as you decide to take,” she says. “But still, you can get many more measurements and it’s outside of the medical setting.”
White-coat hypertension — when patients who don’t seem to have hypertension outside of a medical setting are measured hypertensive within — occurs with an estimated 15 to 30 percent of patients, Piper says.
In the studies her team evaluated, she says, the difference between office and ambulatory monitoring “is enough to move [patients] from the normal to the abnormal, and from the no-treatment into the treatment [range].” Of patients with high office readings, anywhere from 5 to 65 percent were not diagnosed with hypertension after ambulatory monitoring.
The researchers also compared how the different methods predicted future health problems, including heart attacks, sudden cardiac death, congestive heart failure, atrial fibrillation and stroke. Ambulatory monitoring did a better job.
“The USPSTF found convincing evidence that ambulatory blood pressure is the best method for confirming elevated office blood pressure measurements,” the panel concluded, and the method “should be the standard to confirm a hypertension diagnosis at a doctor’s office.”
Home Monitoring Helps
Although there wasn’t enough evidence for firm conclusions on home monitoring, experts agree that it’s helpful. “The American Heart Association has recommended home blood pressure monitoring, because studies suggest it shows some benefit,” says Bauman, who is an AHA spokeswoman.
“I do not treat somebody based [solely] on my office readings,” she says. “Now that may alert me that they have an issue, and if somebody’s blood pressure is sky high, of course we respond to that.” When it comes to screening and diagnosis, she asks patients to measure their blood pressure once a day, and write it down with the time of day. Try different times of day, Bauman suggests: “One day when you get up in the morning, one day when you get home from work, another day at work if you can.” That way, she says, “I can get an idea of what their blood pressure is doing over the course of their life.”
Impact of Change
Ambulatory monitoring is “excellent,” Bauman says, but she doesn’t believe it’s been widely adopted yet for a number of reasons, notably the expense in equipment and time.
Cost considerations could ease, though, if the USPSTF recommendation is made final after the public comment period is over. Task force recommendations can have a big impact on health care, as insurers tend to cover a preventive measure that’s strongly recommended. If the ambulatory monitoring keeps people from being put on medication, Bauman suggests, insurers will notice.
“You don’t want to put people on medication who don’t need it,” she says. “You don’t want to miss putting people on medication who do. And you don’t want to treat a blood pressure reading in the office so you’re upping people’s blood pressure medication when that’s really not what they need.”
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