Blood pressure readings often unreliable

While assessment increasingly occurs outside the office, efforts continue to improve clinician determination of the readings.

By Victoria Stagg Elliott, AMNews staff. June 11, 2007.

The measurement of blood pressure during a doctor visit is fraught with problems that can lead to some cases of hypertension being overlooked or some patients being misclassified as having the condition. That was the message of several presentations at last month's American Society of Hypertension 22nd annual scientific meeting, held in Chicago.

"Of all the procedures done in a doctor's office, measurement of blood pressure is usually the least well performed but has the most important implications for the care of the patient," said Norman M. Kaplan, MD, clinical professor of internal medicine at the University of Texas Southwestern Medical Center, who moderated one of the sessions.

Experts said the in-office assessment is unreliable because blood pressure can be raised or lowered by the presence of the medical professional taking it. The numbers also can be different from one arm to the other or from one minute to the next.

The American Heart Assn. guidelines -- which call for blood pressure to be measured at least five minutes after a patient arrives in the office while he or she is sitting in a chair with the arm supported -- often are not followed. This strategy also can miss patients whose blood pressure peaks at night, first thing in the morning or otherwise out of the office setting, and thus miss patients who might need to lower blood pressure.

"There are so many problems trying to quantify this measurement because it's so variable, and the whitecoat effect is a big problem," said Thomas Pickering, MD, DPhil, director of the behavioral cardiovascular health and hypertension program at Columbia University College of Physicians and Surgeons in New York. "Somehow we assume that these readings have some relevance to what's going on between visits."