ABSTRACT
Purpose To analyze the reliability and validity of a picture-based questionnaire, the Modified Spinal Function Sort (M-SFS). Methods Sixty-two injured workers with chronic musculoskeletal disorders (MSD) were recruited from two work rehabilitation centers. Internal consistency was assessed by Cronbach's alpha. Construct validity was tested based on four a priori hypotheses. Structural validity was measured with principal component analysis (PCA). Test-retest reliability and agreement was evaluated using intraclass correlation coefficient (ICC) and measurement error with the limits of agreement (LoA). Results Total score of the M-SFS was 54.4 (SD 16.4) and 56.1 (16.4) for test and retest, respectively. Item distribution showed no ceiling effects. Cronbach's alpha was 0.94 and 0.95 for test and retest, respectively. PCA showed the presence of four components explaining a total of 74% of the variance. Item communalities were >0.6 in 17 out of 20 items. ICC was 0.90, LoA was ±12.6/16.2 points. The correlations between the M-SFS were 0.89 with the original SFS, 0.49 with the Pain Disability Index, -0.37 and -0.33 with the Numeric Rating Scale for actual pain, -0.52 for selfreported disability due to chronic low back pain, and 0.50, 0.56-0.59 with three distinct lifting tests. No a priori defined hypothesis for construct validity was rejected. Conclusions The M-SFS allows reliable and valid assessment of perceived self-efficacy for work-related tasks and can be recommended for use in patients with chronic MSD. Further research should investigate the proposed M-SFS score of <56 for its predictive validity for non-return to work.
Subject(s)
Disability Evaluation , Musculoskeletal Diseases/rehabilitation , Occupational Injuries/rehabilitation , Surveys and Questionnaires/standards , Adult , Female , Humans , Low Back Pain/diagnosis , Low Back Pain/rehabilitation , Male , Middle Aged , Musculoskeletal Diseases/diagnosis , Occupational Injuries/diagnosis , Pain Measurement , Reproducibility of Results , Self EfficacyABSTRACT
Purpose To develop a modified version of the spinal function sort (M-SFS) by measuring work-related self-efficacy beliefs in patients with chronic low back pain. Methods A mixed method design consisting of three different methods (M1-3) was performed. In semi-structured interviews participants were asked how often they performed the activities of the 50 SFS items in 1 week, and which spinal postures and movements were associated with their back pain (M1). Quantitative analysis of previously obtained SFS data investigated internal consistency, unidimensionality, item response, and floor and ceiling effect (M2). Experts rated the SFS items based on their relevance (M3). The findings from these methods were used within a final scoring system for item reduction. Results From semi-structured interviews with 17 participants, eight new items emerged (M1). Quantitative analysis of 565 data sets (M2) revealed very high internal consistency of all items (Cronbach's alpha = 0.98) indicating item redundancy; unidimensionality of the SFS was supported by principal component analysis; good item response was confirmed by Rasch analysis; and a floor effect of four items depicting very heavy material handling was found. Experts agreed on 8 out of the 50 SFS as relevant (M3). From the original SFS, 12 items met the predefined summary score of 9. Conclusions A modified version of the SFS with 20 items has been developed. Feasibility, reliability and validity of this modified version must be tested before it can be used in clinical practice.
