Ambulatory BP Monitoring More Accurate Than Office Screening

Laurie Barclay, MD

December 23, 2014

Ambulatory blood pressure (BP) monitoring predicts long-term cardiovascular outcomes independent of office BP screening measurements and may therefore improve screening accuracy, according to an updated systematic review for the US Preventive Services Task Force (USPSTF) published online December 23 in the Annals of Internal Medicine.

"Despite the clear importance of accurate diagnosis of high BP, recommendations for BP measurement protocols and rescreening intervals are not based on systematic reviews of the literature, and recommended protocols, such as repeated measurements, are rarely followed in routine health care settings," write Margaret A. Piper, PhD, MPH, and colleagues from the Kaiser Permanente Center for Health Research, Portland, Oregon, and HealthPartners Institute for Education and Research, Minneapolis, Minnesota.

"To help address these issues, newer measurement methods have been developed to reduce error, simplify performance of repeated measurements, evaluate BP throughout the 24-hour cycle, and allow use in nonmedical settings. Evidence-based measurement methods and rescreening intervals could improve the benefits and efficiency of BP screening."

The 2003 USPSTF systematic review did not set a BP measurement reference standard, examine diagnostic accuracy of BP measurement methods and protocols, or identify an optimal rescreening interval. The current update highlighted these issues, in addition to reviewing direct evidence of benefits and harms of screening for high blood pressure in adults.

Specific recommendations include the following:

  • Unless immediate treatment is needed, ambulatory BP monitoring should be the reference standard to confirm elevated office BP screening results to avoid misdiagnosis and overtreatment.

  • Persons at high risk for hypertension on rescreening within 6 years should be screened more often than those without specific risk factors. Risk factors include high-normal BP, older age, above-normal body mass index, and black race.

  • Strategies are needed to improve the accuracy of BP measurement in the clinic.

The evidence review included a search of selected databases through February 24, 2014, for fair- and good-quality trials and diagnostic accuracy and cohort studies performed in adults and published in English. One reviewer abstracted data, a second checked for accuracy, and two reviewers considered study quality.

Findings from the evidence review included the following:

  • In 11 studies, ambulatory BP monitoring predicted long-term cardiovascular outcomes, with hazard ratio ranging from 1.28 to 1.40.

  • In 27 studies, nonoffice confirmatory testing showed that 35% to 95% of persons with elevated BP at office screening remained hypertensive.

  • Persons with isolated clinic hypertension (normotensive after confirmatory testing) had cardiovascular outcomes similar to those in persons who were normotensive at office screening.

  • In 40 studies, incidence of hypertension after rescreening varied considerably at each yearly interval up to 6 years.

  • Intrastudy comparisons showed that risk for hypertension on rescreening within 6 years was at least twice as high in older adults, those with high-normal BP, overweight and obese persons, and blacks.

A limitation of this review is the small number of diagnostic accuracy studies of office BP methods and protocols in untreated adults.

"These results suggest that time and resources might be better directed toward improved measurement accuracy and timely measurement in higher-risk persons rather than measurement of all persons at every office visit," the study authors conclude.

The Agency for Healthcare Research and Quality funded this study and provided grants to its authors. One of the authors also received a grant from the National Heart, Lung, and Blood Institute.

Ann Intern Med. Published online December 23, 2014. Full text

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