German validation of the BIDQ-S questionnaire on body image disturbance in idiopathic scoliosis.

Abstract

The Body Image Disturbance Questionnaire-Scoliosis (BIDQ-S) is a seven-item questionnaire inquiring into patients' worries about back shape and associated problems at school, at work, with friends or family, and whether the patients are avoiding certain activities. The aim of this study was to translate the BIDQ-S into German (G-BIDQ-S), test its reliability, and establish its convergent, divergent, concurrent, and discriminant validity. In a prospective cohort study, 259 patients with idiopathic scoliosis (mean age 30.2; 221 female; mean Cobb angle 43.8°) completed the G-BIDQ-S; Scoliosis Research Society 22-r (SRS 22-r); Patient Health Questionnaire (PHQ-9); Positive and Negative Affect Schedule (PANAS); Questionnaire on Body Dysmorphic Symptoms (FKS); and WHO-5 Well-Being Index. Healthy control individuals matched by age, sex and BMI (n=149; mean age 36.1; 133 female; BMI=23.0) answered the same questions to establish discriminant validity. Discriminant statistics, and Pearson and Spearman correlations were calculated. The G-BIDQ-S proved to be one-factorial, internally consistent (Cronbach alpha=0.87), and stable over time (total score 2.22 vs. 2.21 during retest; retest reliability r=0.79, P<0.001). It correlated significantly with the mean SRS 22-r (r=-0.72, P<0.001) and with Cobb angles (r=0.30, P<0.001)-convergent validity; much less with body mass index (r=0.19, P<0.001)-divergent validity; and with the PANAS (r=0.55, P<0.001), PHQ-9 (r=0.53, P<0.001), FKS (r=0.67, P<0.001), and WHO-5 (r=-0.54, P<0.001)-concurrent validity. The G-BIDQ-S also showed discriminant validity, with a strong difference between the scoliosis group (total score 2.19) and the control group (total score 1.13; P<0.001). The G-BIDQ-S showed good internal consistency, reliability, and convergent, divergent, concurrent, and discriminant validity. This questionnaire is the first one inquiring into patients' body image disturbances that has been validated and is available in German.