Test-retest Reliability in Reporting the Pain Induced by a Pain Provocation Test: Further Validation of a Novel Approach for Pain Drawing Acquisition and Analysis

Reproducibility of a quantitative outcome is usually assessed by means of the intraclass correlation coefficient (ICC). When we are interested in assessing reproducibility from only one sample, we suggest that the study be planned with regards to the expected width of the 95 per cent confidence interval of the ICC. An approximation of this latter width is derived, which allows appraisal of the influence of n the number of subjects and p the number of replicates. Through simulation studies, the approximation is shown to be of good accuracy and can therefore be used reliably. Optimal designs are also discussed such as the optimal distribution between the number of subjects and the number of replicates per subject for a fixed total number of measures. Copyright 2001 John Wiley & Sons, Ltd.

Test-retest reliability of a pain drawing instrument was investigated. Pain drawings of chronic pain patients (n = 51) were scored for percentage of total body surface in pain and location of pain. A test-retest reliability coefficient of r = 0.85 was calculated for a time interval that averaged 71 days. In addition, a percentage of agreement based on distribution of pain over time was calculated at 88.2%. The effect on reliability of age, gender and time-interval differences was investigated. The utility of the pain drawing instrument as a measure of extent of pain and location of pain over time is discussed.