Highlights
- •In persons with chronic pain, a single pain rating produced less than adequate reliability.
- •A composite of 5 daily ratings resulted in reliability above .90.
- •The 5-day composite score was interchangeable with the mean for all available ratings.
- •This supports IMMPACT recommendations for improving assay sensitivity with multiday assessment.
- •Higher measure reliability can improve assay sensitivity, power, and statistical precision.
Abstract
The Initiative for Methods, Measurement, and Pain Assessment in Clinical Trials (IMMPACT)
has reported diminished assay sensitivity in pain treatment trials and recommended
investigation of the causes. Specific recommendations included examination of outcome
measure reliability and lengthening the baseline measurement period to allow more
measurements to be collected. This secondary data analysis evaluated the minimum number
of daily pain intensity ratings required to obtain a reliability of at least .90 and
whether a composite of this smaller number of ratings was interchangeable with the
composite of all ratings. Veterans Affairs medical center patients made 14 daily calls
to an automated telephone system to report their average daily pain intensity rating.
A single daily rating produced less than adequate reliability (intraclass correlation
coefficient = .65), but a composite of the average of 5 ratings resulted in reliability
above .90. A Bland-Altman analysis revealed that the differences between a 5-day composite
and the composite of all ratings were small (mean .09 points, standard deviation = .45;
95% confidence interval = −.05 to .23) and below the threshold for a clinically meaningful
difference, indicating that the 2 measurements are interchangeable. Our results support
the IMMPACT recommendations for improving assay sensitivity by collecting a multiple-day
baseline of pain intensity ratings.
Perspective
This study examined the minimum number of pain ratings required to achieve reliability
of .90 and examined whether this smaller subset of ratings could be used interchangeably
with a composite of all available ratings. Attention to measure reliability could
enhance the assay sensitivity, power, and statistical precision of pain treatment
trials.
Key words
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Article info
Publication history
Published online: October 02, 2014
Accepted:
September 19,
2014
Received in revised form:
September 9,
2014
Received:
May 8,
2014
Footnotes
This material is based on work supported by Jansen Pharmaceutical. A.H., J.G., and R.D.K. were supported by the Veterans Health Administration Health Services Research and Development Service Center of Innovation (CIN 13-407).
The authors have no conflicts of interest to declare.
The project was not registered with clinicaltrials.gov since it began in 2003 prior to the requirement to register.
The views expressed in this article are those of the authors and do not necessarily reflect the position or policy of the Department of Veterans Affairs or the U.S. Government.
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Copyright
Published by Elsevier Inc.
