Development and Psychometric Validation of the Shoulder Problems Assessment Scale: A Culturally Grounded Patient-Reported Outcome Measure With a Hierarchical Stepwise Yes/No Response Format

This study was designed to develop and psychometrically validate the Shoulder Problems Assessment Scale (SPAS), a patient-reported outcome measure intended to assess shoulder-related functional limitations in adults. SPAS was developed to address limitations of existing shoulder scales related to cognitive burden, cultural relevance, and response format, particularly in populations with varying health literacy levels.

The development process followed a four-stage methodological framework. In the first stage, the conceptual framework and initial item pool were established through a comprehensive literature review, semi-structured interviews with patients experiencing shoulder problems, and input from experienced physical therapists. These steps aimed to identify daily activities that commonly provoke functional difficulty in routine life. An initial pool of 34 items was generated, including activity-based items structured in a hierarchical stepwise yes/no format.

In the second stage, content validity was evaluated by an expert panel using the Lawshe method. Items with insufficient content validity or conceptual overlap were revised, combined, or removed. A pilot study was then conducted to assess item clarity, cultural appropriateness, and comprehensibility. Based on expert feedback and pilot results, the item pool was refined and prepared for the main application.

The third stage consisted of a multicenter field application conducted in physical therapy units across multiple regions of Turkey. SPAS was administered to individuals with shoulder problems, followed by the Turkish version of the Shoulder Pain and Disability Index (SPADI) for concurrent validity assessment. A subgroup of participants with stable clinical status completed SPAS again after 3-7 days to evaluate test-retest reliability.

In the final stage, psychometric analyses were performed. Construct validity was examined using exploratory factor analysis (EFA) and confirmatory factor analysis (CFA) with a robust diagonally weighted least squares estimator appropriate for the hierarchical response structure. Reliability was assessed using internal consistency coefficients and intraclass correlation coefficients. Concurrent validity was evaluated through correlations with SPADI scores. Receiver operating characteristic (ROC) analysis was conducted to determine a clinically interpretable cut-off value for SPAS using a SPADI-derived functional limitation reference.