title: Measuring blood pressure for decision making and quality reporting: where and how many measures?
abstract: BACKGROUND
  The optimal setting and number of blood pressure (BP) measurements that should be used for clinical decision making and quality reporting are uncertain.
  
  
  OBJECTIVE
  To compare strategies for home or clinic BP measurement and their effect on classifying patients as having BP that was in or out of control.
  
  
  METHODS
  Secondary analysis of a randomized, controlled trial of strategies to improve hypertension management. (ClinicalTrials.gov registration number: NCT00237692)
  
  
  METHODS
  Primary care clinics affiliated with the Durham Veterans Affairs Medical Center.
  
  
  METHODS
  444 veterans with hypertension followed for 18 months.
  
  
  METHODS
  Blood pressure was measured repeatedly by using 3 methods: standardized research BP measurements at 6-month intervals; clinic BP measurements obtained during outpatient visits; and home BP measurements using a monitor that transmitted measurements electronically.
  
  
  RESULTS
  Patients provided 111,181 systolic BP (SBP) measurements (3218 research, 7121 clinic, and 100,842 home measurements) over 18 months. Systolic BP control rates at baseline (mean SBP<140 mm Hg for clinic or research measurement; <135 mm Hg for home measurement) varied substantially, with 28% classified as in control by clinic measurement, 47% by home measurement, and 68% by research measurement. Short-term variability was large and similar across all 3 methods of measurement, with a mean within-patient coefficient of variation of 10% (range, 1% to 24%). Patients could not be classified as having BP that was in or out of control with 80% certainty on the basis of a single clinic SBP measurement from 120 mm Hg to 157 mm Hg. The effect of within-patient variability could be greatly reduced by averaging several measurements, with most benefit accrued at 5 to 6 measurements.
  
  
  CONCLUSIONS
  The sample was mostly men with a long-standing history of hypertension and was selected on the basis of previous poor BP control.
  
  
  CONCLUSIONS
  Physicians who want to have 80% or more certainty that they are correctly classifying patients' BP control should use the average of several measurements. Hypertension quality metrics based on a single clinic measurement potentially misclassify a large proportion of patients.
  
  
  BACKGROUND
  U.S. Department of Veterans Affairs Health Services Research and Development Service.
authors.affiliation: Center for Health Services Research in Primary Care, Durham Veterans Affairs Medical Center, and Duke University, Durham, North Carolina 27705, USA. ben.powers@duke.edu
authors.forename: Benjamin J
authors.initials: BJ
authors.lastname: Powers
authors.forename: Maren K
authors.initials: MK
authors.lastname: Olsen
authors.forename: Valerie A
authors.initials: VA
authors.lastname: Smith
authors.forename: Robert F
authors.initials: RF
authors.lastname: Woolson
authors.forename: Hayden B
authors.initials: HB
authors.lastname: Bosworth
authors.forename: Eugene Z
authors.initials: EZ
authors.lastname: Oddone
mesh_terms: D000368:Aged; D001794:Blood Pressure; D001795:Blood Pressure Determination / Q000379:methods / Q000592:standards*; D018660:Blood Pressure Monitoring, Ambulatory / Q000379:methods / Q000592:standards; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D006973:Hypertension / Q000175:diagnosis* / Q000188:drug therapy / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D011336:Probability; D011785:Quality Assurance, Health Care