Evidence is becoming overwhelming that ambulatory blood pressure monitoring is the only reliable way to measure blood pressure for both diagnosing hypertension and following patients once they are diagnosed.
Office-based blood pressure measurement is out, be it a one-off reading or a cluster of sequential readings during a single office visit. Ambulatory blood pressure monitoring (ABPM) increasingly is the standard of care.
Mitchel L. Zoler/Frontline Medical News
Dr. Joyce P. Samuel
One recent nail in the coffin of office-based measurement came in a modestly-sized but revealing study reported by Dr. Joyce P. Samuel, a pediatric hypertension specialist at the University of Texas in Houston. She reported her experience directly comparing ambulatory and carefully-done office-based blood pressure measurement in a presentation at the annual meeting of the Pediatric Academic Societies in Baltimore.
Dr. Samuel followed 40 patients age 9-21 years whom she had previously diagnosed with essential hypertension (children with a systolic blood pressure at or above the 95th percentile for sex, age, and height), and repeatedly measured their blood pressures by both ambulatory and office-based readings at 2-week intervals as she searched for the best combination of antihypertensive drugs for each patient. She sent patients home for 24 hours of blood-pressure monitoring with an ambulatory device, and when they returned to her office the next day, she performed an office-based measurement using meticulous technique: Each child was seated and calm, measured on the right arm, with four measurements taken sequentially at about 1 minute intervals with the first reading discarded and the remaining three averaged.
Over the course of several months, she collected 173 paired ambulatory and office-based systolic blood pressure readings from individual patients. Substantial differences between the two forms of measurement were remarkably common. In 20% of the pairs, the ambulatory systolic reading was at least 10 mm Hg higher than the office-based reading, and for some pairs the differences ran as high as 30 mm Hg. In an additional 32% of the paired readings, office-based systolic pressure ran at least 10 mm Hg higher and in some cases as much as 35 mm Hg higher than the ambulatory reading.
Dr. Samuel also analyzed her findings a different way to assess the clinical consequences of these differences based on whether a child’s systolic pressure identified the patient as normotensive, hypertensive, or prehypertensive (a systolic pressure at the 90-94th percentile for the child’s age, sex and height). She found that the diagnoses matched for only 49% of the paired measurements. In 24% of the paired readings, ABPM identified children with hypertension that was not seen with concurrent office-based measurement, cases of masked hypertension. In 17% of the pairs, office-based measurement diagnosed hypertension that was not confirmed by ABPM, cases of white-coat hypertension. The remaining 10% of pairs were mismatched by showing normotensive with one method and prehypertensive with the other method. Dr. Samuel searched for any consistent patterns in these differences and found none. The disparate results with ambulatory and office-based measurements seemed almost random, with no correlation with age, sex, race, the medications patients received, or how many times a patient had already undergone dual blood-pressure monitoring. Individual patients had no meaningful differences between some of their paired measurements but had a meaningful disparity for others.
“We were unable to predict discrepancies,” said Dr. Samuels.
“You can’t get around it, you need ambulatory blood pressure monitoring to make the best diagnosis” of hypertension, she told me. “We need to push to make ambulatory monitoring more available. I am moving toward believing that ambulatory blood pressure monitoring must be routinely done on everyone. This is what the data suggest.”
It’s also where medicine is headed. In 2015, the U.S. Preventative Services Task Force (USPSTF) issued new recommendations for hypertension screening in adults aged 18 years or older, indicating that there was “convincing evidence that ABPM is the best method for diagnosing hypertension,” and the agency further recommended that ABPM is “the reference standard for confirming the diagnosis of hypertension.” Another endorsement of ambulatory blood pressure monitoring came out last year from the International Society for Chronobiology.
Recommendations are not yet as evolved for children. The USPSTF last weighed in on screening kids for hypertension in 2013, and said the evidence as of then was “insufficient” to assess the benefits and harms of screening for hypertension in children and adolescents. That document endorsed careful office-based blood pressure measurement, which highlights how recently expert sentiment has shifted on the issue of measurement. In response to the USPSTF 2013 statement, the American Academy of Pediatrics noted that it continued to back recommendations that are more than a decade old from the National High Blood Pressure Education Program that called for hypertension screening in children starting when they are 3 years old. Neither of these two groups has made any recent statement about the preferred method to measure blood pressure.