Connecticut cardiologist demonstrates that averaging six blood pressure readings leads to more accurate diagnoses
Doctors can make important treatment decisions based on one or two blood pressure readings. Yet it’s known that readings can be misleading, often due to white coat hypertension (that is, a patient’s anxiety about being in the doctor’s office and having his or her blood pressure taken), talking or active listening, distended bladder, cuff over clothing, smoking within 30 minutes of measurement, back unsupported or an unsupported arm while sitting or standing.
One cardiologist has demonstrated that taking an average of six readings during a patient visit can lead to more accurate results and appropriate treatment.
Early this summer, Robert Smith, MD, a practicing cardiologist at Saint Francis Hospital and Medical Center in Hartford, Conn., and an associate professor of medicine at the University of Connecticut School of Medicine in Farmington, released the results of his study designed to compare single in-office automated blood pressure readings to the average of multiple automated blood pressure readings.
Readings were collected on 187 adult patients using a Welch Allyn Connex® Vital Signs Monitor (Model 6300) with Office Profile and automatic base-lining technology enabled. Smith’s analysis showed that blood pressure diagnosis varies over a range of consecutive readings, suggesting that it can be important to calculate an average blood pressure in order to obtain the most accurate representation of the true blood pressure in the doctor’s office.
“The purpose of this study was to compare single in-office blood pressure readings to average in-office blood pressure readings and observe the differences in accuracy and potential variation in diagnoses between the two methodologies,” he said. “An inaccurate diagnosis of high blood pressure could lead to the overprescribing of blood pressure-lowering medications, which may result in adverse events associated with hypotension, which is the last thing we want for patients. As doctors our mantra is and always will be, ‘first, do no harm.’”
Reclassified patients
To mimic the true office experience, Smith and his staff started the first blood pressure measurements at varied times after patients entered the exam room one to three minutes into the test. Five subsequent measurements were taken at intervals of one minute, and the monitor automatically calculated a recommended average that included up to six of these measurements.
Results showed that with averaged readings, half of the patients previously classified as hypertensive using the single reading methodology were reclassified into pre- and normotensive categories. More than half of the patients that would have required the physician to provide hypertensive care did not display the medical need with an averaged reading.
Smith described another interesting finding of his study: In general, it is recommended that the first blood pressure reading in the office visit be eliminated, the assumption being that that will be the highest, he said. “When we evaluated these 187 people, we found that 41 percent of the time, their first reading was the highest; but with many, their second, third, fourth or even last reading was higher. This emphasized, in my practice, that using averaging as a means of evaluating people has a lot of merit.”
Patients were pleased with the procedure, Smith said in response to a question from Repertoire. “They are engaged and interested in the results. And when I see them, a lot of uncertainty is eliminated. You can either reassure someone that they are normal, or that they are not normal and should take medication. If they already are on medication, you get an indication whether it’s working effectively or not.
“Time is a concern for everyone in a busy office,” he said. “But in our practice, [taking six readings] didn’t slow me down at all. If anything, it gave me useful information, so that when I walked into the exam room, we were pointed in the right direction, because we were dealing with accurate numbers.”
Based on the findings of the study, Smith’s practice has adopted the averaging technique as standard routine. “It has improved the overall quality of care. At this point, if we tried to go back, we would be unhappy, and our patients would be unhappy.”
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