Accuracy of retrospective pain measurement in patients with chronic pain.

The use of pain scales that refer to a past time period is thereby based on the assumption that patients accurately remember their 'average', 'greatest' and 'least' pain. The present study addresses the validity of numerical pain rating scales that refer to a past period of time (herein, the past 7 days). Routine data from 94 patients with chronic pain were retrospectively analysed. Pain questionnaire data on the greatest, least and average pain during the past week and on current pain were compared with the mean value of entries in a pain diary from the corresponding period. The retrospectively assessed average, greatest and least pain values were consistently slightly higher than the corresponding values of daily current pain measured for the studied collective of chronic pain patients. Current pain (at the time of answering the questionnaire) better represents daily currently measured pain [intraclass correlation (ICC)=0.885] than retrospective individual measurements. The greatest correlation with averaged diary data was shown by the combination of questionnaire data on average, least and current pain (ICC=0.911). The high correlations between the questionnaire and diary data support the validity of retrospective pain surveys. However, the current status influences recall. Thus, composite retrospective pain data improve with the addition of current pain.