Why In-Office Blood Pressure Measurements May Be a Problem

Why the doctors office may not be the best place to measure blood pressure.

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It looks like the diagnosis of high blood pressure may finally be moved out of the doctor’s office, and out into the home, at least if the United States Preventive Services Task Force (USPSTF) has its way.

In December, 2014, the USPSTF issued new draft recommendations on diagnosing hypertension, which strongly urge doctors to use ambulatory blood pressure monitoring (ABPM) before committing patients to lifelong antihypertensive therapy. Essentially, the USPSTF is making public a dirty little secret - namely, that the blood pressure measurements obtained in doctors’ office are often just not accurate enough. ABPM is a much more accurate method for determining whether a person really has or does not have stage 1 hypertension, and its use would prevent many cases of over-treatment and (less commonly) under-treatment.

It seems quite likely that at least some doctors (and probably payers) will object to these new guidelines, and that at least some pressure will be brought to bear to get the USPSTF to modify it’s proposed recommendations before they are finalized. The problem for doctors is that ABPM is relatively cumbersome to provide, is often not readily available, and the requirement to use it threatens to further complicate doctors’ already complicated professional lives. The problem for payers is that ABPM is expensive, and they won’t like the prospect of having to pay for hundreds of thousands of ABPM tests each year.

The difficulty with such objections is that the USPSTF is fundamentally correct in this case. The blood pressure measurements obtained in the doctor’s office really are often misleading, and can lead to inappropriate medical care.

Why Office Blood Pressure Measurements Are A Problem

When you have your blood pressure measured in a doctor’s office, the measurement that is recorded immediately becomes your “official” blood pressure - as if blood pressure is a static value, like your weight or height. But blood pressure is not a static value. It fluctuates quite a bit from minute to minute, depending on the immediate needs of your cardiovascular system. Unless it is performed under carefully defined conditions, a single blood pressure measurement might be little better than a random sampling of these normally fluctuating values.

To try to get around this problem, the "standard" blood pressure measurement is defined as taking place under the condition of “quiet rest,” and the studies demonstrating the benefits of diagnosing and treating hypertension are based on these standards.

Here are the requirements for a “standard” blood pressure measurement:

  • The patient should be placed in a comfortable, warm, and quiet environment.
  • The patient should not have had caffeine or tobacco products for at least 30 minutes.
  • The patient should be quietly seated, with their back supported and straight, and with both feet supported on the floor.
  • The patient should remain at rest in this environment for at least 5 minutes.
  • After these conditions are met, the doctor or nurse should quietly take the patient’s blood pressure at least twice, preferably with a 5-minute interval between readings.
  • If the two measurements vary by more than 5 mm Hg, more readings should be performed, with similar intervals between recordings, until the recordings agree.

We all know what actually happens. The patients arrives on time for his/her appointment, but then languishes in a crowded and stuffy waiting room. Finally, the patient is rushed back into a cold examination room, and is ordered to strip down and put on a flimsy examination gown with broken ties. Then, all but naked to the elements, the patient sits as instructed on an icy examination table, with no back support and with legs dangling. A harried doctor or nurse finally rushes in, slaps on a blood pressure cuff, and while taking the blood pressure simultaneously engages the patient in a Q & A, or begins doing two or three other things that are on their “pay for performance” checklist. And there is virtually no chance of getting a second blood pressure reading 5 minutes later.

So, in many (if not most) cases, what you get in a doctor’s office is more nearly a random sampling of a fluctuating blood pressure, in conditions far different from “quiet rest.” By definition, such a measurement should not be used to diagnose stage 1 hypertension.

Despite these shortcomings, if the measured blood pressure is well within the normal range (less than 120 mm Hg systolic and less than 80 mm Hg diastolic), no harm is done. And if the blood pressure is sufficiently high (160 mm Hg systolic), it can be safely assumed that the hypertension is real, and treatment can be instituted. The problem arises when the blood pressure in the office is in the range of milder, stage 1 hypertension. Is this really hypertension? Or is it merely an artifact of a suboptimal sampling method?

Doctors, of course, do not blame themselves. Patients in whom the blood pressure is elevated in the doctor’s office, and normal at home, are said to have “white coat hypertension.” And while it is likely that white coat hypertension actually exists, it does seem just a bit presumptuous of doctors to invent a new disease, and assign it to their patients, when in many cases they are simply failing to measure blood pressure as it is supposed to be measured.

The Advantage of ABPM (And HBPM)

The advantage of ABPM is that it does not rely on one or two blood pressure readings under supposedly controlled conditions. Instead, ABPM samples blood pressures at frequent intervals over a 24 hour period - during all the fluctuations that normally occur in a day. The presence or absence of hypertension is determined by the average blood pressure during the entire day. The diagnosis of hypertension with ABPM has been well-validated, and is significantly more accurate than the diagnosis of stage 1 hypertension made in the doctor’s office.

An alternative to ABPM is home blood pressure monitoring (HBPM). There are several advantages of HBPM that make it more attractive than ABPM for diagnosing and managing hypertension, and most doctors believe it to be a reasonable alternative. The USPSTF draft document clearly indicates a preference for HBPM over the doctor’s office for diagnosing hypertension.

What All This Means To You

It is likely that there will be a protracted battle before doctors and payers agree with the USPSTF that stage 1 hypertension should be diagnosed only after ABPM (or HBPM) confirms the diagnosis. What you should know, if you have been told you have stage 1 hypertension (or prehypertension), and your doctor is recommending lifelong treatment, is that these confirmatory tests are available today, and it makes sense to ask for them. Learn about ABPM and HBPM, and ask your doctor if it would be reasonable to use such testing to confirm that you actually have hypertension before beginning medical treatment.

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Article Sources
  • Draft Recommendation Statement: High Blood Pressure in Adults: Screening." US Preventive Services Task Force. December 2014. http://www.uspreventiveservicestaskforce.org/Page/Document/RecommendationStatementDraft/hypertension-in-adults-screening-and-home-monitoring (Accessed January, 2015).
  • Pickering TG, Miller NH, Ogedegbe G, et al. Call to action on use and reimbursement for home blood pressure monitoring: executive summary: a joint scientific statement from the American Heart Association, American Society Of Hypertension, and Preventive Cardiovascular Nurses Association. Hypertension 2008; 52:1.