[Do questionnaires for the assessment of change really assess change?]

Two methods for the assessment of change are evaluated: (1) subjects' ratings of the outcome taken after termination of the treatment, and (2) comparison of test scores taken before the beginning and after termination of the treatment.

Included in the analysis are 82 subjects with chronic headache and/or back pain who participated in psychological group treatment for pain. They were given an outcome rating scale with 15 items (ORS) after therapy in addition to pain diaries and questionnaires for the assessment of physical symptoms, mood and quality of life. Diaries and questionnaires were filled in twice, before and after therapy.

The ORS demonstrates satisfying psychometric properties. Internal consistency is 0.94 (Cronbach's alpha) and retest reliability is 0.74. Correlations of this scale with outcome criteria based on pre-post comparisons, however, are mostly nonsignificant. Significant correlations are found when the ORS scores are related to the questionnaire scores after therapy.

It is concluded that, contrary to the formulation of the items, the ORS scale does not so much assess change, but rather depicts the state of the subjects at the time the assessment is made.