Chronic low-back pain: Intercorrelation of repeated measures for pain and disability

Abstract

Subjective experience of pain and disability was assessed for 4-5 weeks on a weekly basis in 14 consecutive out-patients complaining of low-back pain and/or leg pain that had lasted for at least 6 months. The following measures were used for assessment: a visual analogue scale (VAS) (present pain and worst pain during preceding 2 weeks), a short-form McGill Pain Questionnaire (SF-MPQ), the Pain Disability Index (PDI) and the pain drawing. In addition, psychological variables of pain experience were evaluated with the Comprehensible Psychopathological Rating Scale (CPRS). When the median of the variation coefficient for repeated measures was compared, the most stable measures were, in rank order: PDI, total number of words chosen in the SF-MPQ and worst pain during the preceding two weeks (VAS). The Spearman correlation showed statistically significant intercorrelation for present pain assessed with the VAS score, for the sensory word score of the SF-MPQ and for the PDI. Especially the PDI, which represents a global score for disability, showed very little test-retest variability and a high intercorrelation with the other methods of assessment, i.e. the pain drawing, the VAS scale for pain and the SF-MPQ. Total marks in the pain drawing was the best pain drawing subscale with respect to both test-retest variability and intercorrelation with other assessment methods. Subjective pain experience and disability measures, such as those tested, apparently measure very similar aspects, whereas subtle differences become evident when subscales are compared.