February 1, 1988Journal of Hypertension
The use of ambulatory blood pressure monitoring to improve the accuracy and reduce the numbers of subjects in clinical trials of antihypertensive agents
Why the study?
Does ambulatory blood pressure monitoring improve accuracy and reduce required sample sizes in clinical trials of antihypertensive agents?
Population
42 subjects
Comparison
Ambulatory blood pressure monitoring using a… vs Mercury manometer (for accuracy comparison)
Design
Other
Authors
Discussion
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Implication
ABPM may enable smaller antihypertensive trials via lower variability; leaves open superiority for routine accuracy pending larger validation.
Key Points
- To determine whether daytime ambulatory blood pressure monitoring can improve measurement precision and lower the sample size required for clinical trials of antihypertensive agents.
- Adapted a commercial stationary unit into a low-cost ambulatory blood pressure monitor and validated its accuracy against a standard mercury manometer over 4 years.
- Obtained blood pressure readings in the sitting position at 30-minute intervals throughout the waking day in N=42 subjects to assess reproducibility and diurnal variation.
- Repeated measurements in 42 subjects showed no detectable placebo effect, with a mean difference between two readings of 1.9/-0.33 mmHg and standard deviations of 8.1/5.6 mmHg.
- Power calculations indicate this precision permits the detection of an 8/5 mmHg treatment difference with approximately 16 subjects.
- Blood pressure remained stable throughout the waking day, though measurement variability increased substantially when monitoring intervals were reduced to 4 hours.
Structured PICO
Does ambulatory blood pressure monitoring improve accuracy and reduce required sample sizes in clinical trials of antihypertensive agents?
P
Population
42 subjects
I
Intervention
Ambulatory blood pressure monitoring using a low-cost device with readings at half-hourly intervals over the waking day
C
Comparator
Mercury manometer (for accuracy comparison)
O
Outcome
Accuracy and variability of blood pressure readingssurrogate
Ambulatory blood pressure monitoring reduces reading variability and eliminates the placebo effect, significantly reducing the sample size needed for antihypertensive clinical trials.
Cite This Study
Conway et al. (1988) studied this question.