Simple pain rating scales hide complex idiosyncratic meanings

Assumptions of reliability and consistency of self-report of pain by patien ts using visual analogue scales (VAS) and numerical rating scales (NRS) are based on narrow considerations of possible sources of error. This study ex amined patients' use of VASs and NRSs, by their own description, with parti cular attention to rating of multiple pains, of different dimensions of pai n, and of interpretation and use of lower and upper endpoints and increment s on the scales. These have implications for the approximation of the scale s to psychometric requirements. An interview developed from a small pilot p roject was given to 78 volunteer chronic pain patients embarking on a pain management course, and consisted of both forced choice questions and free r esponse. Data are described with reference to lack of concordance between p atients and of consistency within patients; responses suggested that rating s incorporate multiple partially differentiated dimensions of pain, with pa rticular importance placed on function or mobility. Labels assigned to scal e endpoints by researchers, whether lexical or numerical, appeared to affec t their use; however, covert relabelling of scale points was revealed in fr ee response. The action of arriving at a rating is better conceptualised as an attempt to construct meaning, influenced by and with reference to a ran ge of internal and external factors and private meanings, rather than as a task of matching a distance or number to a discrete internal stimulus. (C) 2000 International Association for the Study of Pain. Published by Elsevier Science B.V. All rights reserved.