Abstract
Background: Instruments for the psychological assessment of people with idiopathic scoliosis (PwIS) are required to design and plan interventions and services for this population. The few instruments available such as the Scoliosis Research Society Outcome Instrument1 rely on single item measures, omit important domains such as coping, and are not validated for use by the UK population. Therefore, the aim of this study was to assess the psychometric properties of a battery of existing instruments to measure the psychosocial functioning of PwIS in the UK.
Methods: A non-experimental design was used to examine the psychometric properties of the following scales: Functional Dimensions of Coping (FDC); Iowa Body Image (IBI); Acceptance of Scoliosis (AoS); Quality of Life Profile for Spine Deformities (QoLPSD); Multidimensional Health Locus of Control (MHLoC); and the McGill Pain Questionnaire (MPQ). A sample of 126 PwIS (88% female) with a mean age 39.0 years. The number with thoracic, thoraculumbar, double major and lumbar curves was 26 (41.3%), 16 (25.4%), 16 (25.4%) and 5 (7.9%) respectively. Sixty one (48.4%) had undergone some form of surgery. The instruments were assessed in terms of factor structure (factor analysis); internal reliability (Cronbach’s alpha); discriminant validity (examining significant correlations with > 5% overlap in variance, i.e. r > 0.022); construct validity (correlations between one construct such as HRQoL and another construct that is expected to covary such as pain); and sensitivity (correlations between scores on the instruments and patient factors such as Cobb angle).
Results: The instruments had clearly defined factor structures that confirmed previous research and the sub-scales were universally reliable (Cronbach’s alpha ≥ 0.7; range 0.7 – 0.95). Except for MHLoC the instruments possessed adequate discriminant validity. Construct validity was demonstrated by 70% overlap in variance between AoS and HRQoL – Psychosocial Functioning subscale and significant correlations between HRQoL – Sleep Disturbances and HRQoL – Back Pain with all the MPQ subscales. Subscales on all the instruments (except MHLoC) were sensitive to differences in patient variables (e.g. age and Cobb angle).
Conclusion: Given the excellent psychometric properties of the instruments used, we propose a new outcome measure ‘The Scoliosis Psychosocial and Pain Profile Inventory’ (SPPPI), that consists of the following instruments: FDC, IBI, AoS, QoLPSD, and MPQ. Further research is needed investigate the test re-test reliability and responsiveness of the SPPPI after the delivery of medical, surgical and psychosocial interventions.
The abstracts were prepared by Mr Colin E. Bruce. Correspondence should be addressed to Colin E. Bruce, Consultant Orthopaedic Surgeon, Alder Hey Children’s Hospital, Eaton Road, Liverpool, L12 2AP.
References:
1 Haher TR et al. Results of the Scoliosis Research Society instrument for evaluation of surgical outcome in adolescent idiopathic scoliosis: a multicenter study of 244 patients. Spine, 1999; 24: 1435–1440. Google Scholar
