How do minor changes in the definition of blood pressure control affect the reported success of hypertension treatment?
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.
Green
Beverly B
BB
Center for Health Promotion, Group Health Cooperative, Seattle, Wash, USA. green.b@ghc.org
Kaplan
Robert C
RC
Psaty
Bruce M
BM
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
D000959:Antihypertensive Agents