Multiple Blood Pressure Readings Give More Accurate Diagnosis

One reading at your doctor's office is not enough information to accurately gauge your blood pressure, according to new research.

A condition known as "white coat hypertension," or a spike in blood pressure at the doctor's office, can often give false reading, says the study's lead author, Benjamin Powers, M.D., at Duke University Medical Center.

"Collecting just a few - five or six - blood pressure readings from home will help your doctor make much better decisions about whether your blood pressure is in or out of control," Dr. Powers says.

According to the American Heart Association, an adult’s blood pressure should be less than 120 systolic (the upper number in the reading) over less than 80 diastolic (the lower number). A reading of 120 to 139 over 80 to 89 is considered prehypertension, and a reading of 140 or more over 90 or more is considered hypertensive.

Comparing measurements

For the study, Dr. Powers and his colleagues evaluated 444 U.S. veterans with high blood pressure. Their blood pressure was considered uncontrolled, even though most took multiple blood pressure-lowering medications. They then compared blood pressure readings taken in three settings -- at home, in a doctor's office, and at a clinical research setting -- at the study start and again at six, 12, and 18 months. The measurements varied widely.

Only a third of the blood pressure measurements were consistently categorized as in or out of control by all three measures, the researchers found.

Several readings preferred

The results point to the importance of getting multiple measures from different settings. Using just one reading as the basis for prescribing or adjusting blood pressure medication could endanger patients who suffer from "white coat" hypertension, the researchers say. They recommend using an average of at least six readings to get the best estimate of true blood pressure.

Home monitoring of blood pressure is becoming more popular. About 43 percent of people with high blood pressure use home monitors. Dr. Powers says the study results support recent calls for reimbursement of home blood pressure monitoring.

"I think patients should expect their doctors to make decisions based on home blood pressure [in addition to other measures]," he says. But, he adds, those who use a home blood pressure monitor should get it validated for accuracy at their doctor's office.

Always talk with your health care provider to find out more information.