(Hypertension. 1995;25:294-301.)
© 1995 American Heart Association, Inc.
Articles |
Feasibility Study of N-of-1 Trials With Blood Pressure Self-Monitoring in Hypertension
From the Centre de Médecine Préventive Cardio-Vasculaire (G.C., M.D., G.B., J.M.) and the Medical Informatics Department (G.C.), Broussais Hospital, Paris, France.
Abstract The objective of this study was to assess individual
responses to antihypertensive treatment by N-of-1 trials using blood
pressure self-monitoring in 79 patients of both sexes referred to a
hypertension clinic. Thirty-five patients who remained untreated (study
1) and 44 N-of-1 trial participants (study 2) were consecutively
selected if their clinic blood pressure was between 160/95 and 220/115
mm Hg and there were no hypertensive complications. Blood pressure was
measured daily at home for 21 days (three consecutive measures, morning
and evening). Each N-of-1 trial was a single-blind treatment consisting
of two successive 10-day treatment pairs, each pair comprising 5 days
of placebo followed by 5 days of 20 mg enalapril once daily in the
morning. Study 1 showed no significant blood pressure regression toward
the mean over 20 days and justified the choice of 5-day treatment
periods in study 2. In study 2, blood pressure fell significantly 12
hours after the first administration of enalapril and rose within 24
hours of the end of the 5-day active treatment period. Using evening
blood pressure values (12 hours after enalapril intake) from the first
treatment pair, 33 patients were classified as responders (diastolic
blood pressure fall 
6 mm Hg). In 16 of these 33 patients, the fall
in blood pressure above 6 mm Hg was not maintained in the morning, 24
hours after drug intake. Response reproducibility was tested by
comparison with the second treatment pair: the observed agreement was
only 0.71 (chance-corrected agreement: 0.34) when defined according to
both evening and morning values. N-of-1 trial methodology can be useful
for decision making in the care of individual patients. It can be based
on the use of home blood pressure determinations, provided that there
are at least 30 readings in each 5-day trial period. The individual
agreement between the antihypertensive responses to two successive
enalapril treatment periods is only moderate and is not sufficient to
justify using this design for performing in individual patients
randomized comparison of an angiotensin-converting enzyme inhibitor and
another antihypertensive drug.
Key Words: randomized controlled trials • enalapril • antihypertensive therapy • angiotensin-converting enzyme inhibitors • self care • monitoring, physiologic • blood pressure monitors
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