Construct validity and internal consistency of the modified Persian version of the STarT Back Screening Tool

Considering the importance of non-specific low back pain (NSLBP) and its increasing spread, the need for instruments for the accurate diagnosis of back pain is evident in order to offer more effective treatment. One such instrument is the STarT Back Screening Tool (STarT) which is examined by numerous studies, while some of its psychometric dimensions still require attention. Therefore, the objective of this study was to assess the internal consistency and construct validity of this questionnaire to propose a modified version.

In this cross-sectional study, the data of 295 patients with NSLBP were analyzed. Cronbach's alpha was used to assess internal consistency, and exploratory factor analysis (EFA) and confirmatory factor analysis (CFA) were performed to assess construct validity. The Χ2/df, GFI, CFI, and RMSEA indices were also utilized as the goodness-of-fit criteria. Data analysis was performed in SPSS, AMOS, and EQS programs.

Goodness-of-fit indicators were calculated for the original Persian version of the questionnaire, showing an improper fit (RMSEA = 0.162). According to the measures of sampling adequacy (MSA) of the questions, Questions 1 and 8 were deleted, resulting in an improved index (RMSEA = 0.062). All the regression coefficients in the CFA model were significant (p < 0.001for all 7 parameters).

Based on the results, the modified Persian version of the STarT is simpler and more practical than the previous version, serving as a valid and reliable tool for assessing patients with low back pain. With respect to the goodness-of-fit indices, we recommend that more studies with larger samples be conducted on different populations.