title: How do minor changes in the definition of blood pressure control affect the reported success of hypertension treatment?
abstract: OBJECTIVE
  In 1999, the first reporting year of the Health Plan Employer Data and Information Set, our organization noted a significant difference in the proportion of patients with controlled blood pressure (BP) when the target was changed from < 140/90 mm Hg to < or = 140/90 mm Hg. We compared these data with a second larger dataset to determine if these findings were an isolated or common phenomenon and to determine what factors influenced this difference.
  
  
  METHODS
  Subjects were drug-treated hypertensive patients. Blood pressure measurements were taken from outpatient medical records.
  
  
  RESULTS
  The percent of hypertensive patients with controlled BP levels was significantly greater (P <.001) when the cutoff of < or = 140/90 mm Hg was used rather than <140/90 mm Hg. When a single BP measurement was used to estimate control, the percent of patients with controlled hypertension increased 12.7% simply by changing the definition to include the level of systolic BP = 140 mm Hg or diastolic BP = 90. When multiple BP readings were used to estimate control, the difference was much less pronounced (2.7%).
  
  
  CONCLUSIONS
  When evaluating the success of hypertension treatment, defining BP control as a BP of < or = 140 mm Hg systolic and < or = 90 diastolic mm Hg will result in significantly more people having controlled BP than when <140 mm Hg systolic and <90 mm Hg diastolic are used. This difference is most likely the result of end-digit preference. The use of multiple measures reduces this effect. Policy makers and guideline authors should consider these aspects when setting BP goals.
authors.affiliation: Center for Health Promotion, Group Health Cooperative, Seattle, Wash, USA. green.b@ghc.org
authors.forename: Beverly B
authors.initials: BB
authors.lastname: Green
authors.forename: Robert C
authors.initials: RC
authors.lastname: Kaplan
authors.forename: Bruce M
authors.initials: BM
authors.lastname: Psaty
mesh_terms: D000328:Adult; D000368:Aged; D000959:Antihypertensive Agents / Q000627:therapeutic use*; D001794:Blood Pressure / Q000187:drug effects*; D005260:Female; D006264:Health Benefit Plans, Employee / Q000592:standards; D006279:Health Maintenance Organizations / Q000592:standards*; D006801:Humans; D006973:Hypertension / Q000188:drug therapy* / Q000503:physiopathology; D008297:Male; D006278:Medicare; D008875:Middle Aged; D015205:Northwestern United States; D019984:Quality Indicators, Health Care; D016896:Treatment Outcome
chemical_list: D000959:Antihypertensive Agents