Beliefs about surgery: Development and validation of an instrument to assess cognitive representations about surgery, in the context of a chronic illness.

OBJECTIVES: Within a trial of medical and surgical treatments for gastro-esophageal reflux disease (GORD), involving randomised arms and preference arms, we tested the applicability of the Beliefs about Medicines Questionnaire (BMQ) and developed and tested the validity of a new Beliefs about Surgery Questionnaire (BSQ). METHODS: Patients with GORD (N = 43) were interviewed to elicit their beliefs about medical and surgical treatments. These contributed to the development of BSQ items. The BMQ and BSQ were completed by trial participants at baseline (randomised trial: N = 325; preference trial: N = 414). Factor analysis and discriminant function analysis were used to assess validity. RESULTS: Principal components analysis (PCA) largely replicated the four-factor BMQ structure. PCA of the combined BMQ/BSQ yielded six factors explaining 54.5% variance. BSQ items loaded onto distinct factors, demonstrating divergence from BMQ. As predicted, BMQ/BSQ scores enabled correct classification of 78.5% of participants to medication and surgery groups in the preference trial (chi(2)(6) = 205.9, p < 0.001) but only 54.5% (no better than chance) in the randomised trial (chi(2)(6) = 9.4, p = 0.154). CONCLUSIONS: The BSQ is a valid measure of perceptions about surgical treatments for GORD. With the BMQ, it provides information that may guide patients' choices about treatment. This measure may be applicable to other conditions.