Rasch analysis resulted in an improved Norwegian version of the Pain Attitudes and Beliefs Scale (PABS)

Abstract

Background and aimThere is evidence that clinicians’ pain attitudes and beliefs are associated with the pain beliefs and illness perceptions of their patients and furthermore influence their recommendations for activity and work to patients with back pain. The Pain Attitudes and Beliefs Scale (PABS) is a questionnaire designed to differentiate between biomedical and biopsychosocial pain attitudes among health care providers regarding common low back pain. The original version had 36 items, and several shorter versions have been developed. Concern has been raised over the PABS’ internal construct validity because of low internal consistency and low explained variance. The aim of this study was to examine and improve the scale's measurement properties and item performance. MethodsA convenience sample of 667 Norwegian physiotherapists provided data for Rasch analysis. The biomedical and biopsychosocial subscales of the PABS were examined for unidimensionality, local response independency, invariance, response category function and targeting of persons and items. Reliability was measured with the person separation index (PSI). Items originally excluded by the developers of the scale because of skewness were re-introduced in a second analysis. ResultsOur analysis suggested that both subscales required removal of several psychometrically redundant and misfitting items to satisfy the requirements of the Rasch measurement model. Most biopsychosocial items needed revision of their scoring structure. Furthermore, we identified two items originally excluded because of skewness that improved the reliability of the subscales after re-introduction. The ultimate result was two strictly unidimensional subscales, each consisting of seven items, with invariant item ordering and free from any form of misfit. The unidimensionality implies that summation of items to valid total scores is justified. Transformation tables are provided to convert raw ordinal scores to unbiased interval-level scores. Both subscales were adequately targeted at the ability level of our physiotherapist population. Reliability of the biomedical subscale as measured with the PSI was 0.69. A low PSI of 0.64 for the biopsychosocial subscale indicated limitations with regard to its discriminative ability. ConclusionsRasch analysis produced an improved Norwegian version of the PABS which represents true (fundamental) measurement of clinicians’ biomedical and biopsychosocial treatment orientation. However, researchers should be aware of the low discriminative ability of the biopsychosocial subscale when analyzing differences and effect changes. ImplicationsThe study presents a revised PABS that provides interval-level measurement of clinicians’ pain beliefs. The revision allows for confident use of parametric statistical analysis. Further examination of discriminative validity is required.