The purpose of this study is to develop and psychometrically validate the Shoulder Problems Assessment Scale (SPAS), a culturally grounded patient-reported outcome measure designed to assess shoulder-related functional limitations in Turkish adults using a hierarchical stepwise yes/no response format. SPAS items are structured as four ordered difficulty thresholds for common daily activities, allowing respondents to indicate the point at which difficulty first begins while keeping the response task cognitively simple.

Scale development followed a four-stage process including literature review, semi-structured patient interviews, expert content validation (Lawshe method), pilot testing, and main field testing in multiple physical therapy units across Turkey. In the main application, SPAS was administered to individuals with shoulder problems and evaluated for construct validity using exploratory and confirmatory factor analyses, reliability using internal consistency and test-retest intraclass correlation coefficients (3-7 days), and concurrent validity through correlation with the Shoulder Pain and Disability Index (SPADI). Receiver operating characteristic (ROC) analysis was performed to derive a clinically interpretable SPAS cut-off value using a SPADI-based functional limitation reference. The study aims to provide a valid, reliable, practical, and culturally appropriate PROM that can be used in routine clinical assessment and research in Turkey.

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.

SPAS consists of 12 activity-based items, each comprising four ordered difficulty levels. Respondents indicate the level at which difficulty first appears, reflecting a threshold-based approach to functional limitation rather than graded symptom intensity. Total scores range from 0 to 48, with higher scores indicating greater functional limitation. The study aims to provide a valid, reliable, and practical instrument for assessing shoulder-related functional limitations in clinical and research settings.

Inclusion Criteria:

Adults aged 18-80 years Presence of shoulder-related pain and/or functional limitation Referred to or receiving treatment in a physical therapy or rehabilitation unit Ability to understand and respond to the questionnaire items Provision of written and verbal informed consent

Exclusion Criteria:

Neurological disorders affecting upper extremity function Systemic inflammatory or rheumatologic diseases involving the shoulder Severe cognitive impairment or psychiatric conditions that may interfere with questionnaire completion Acute trauma or fracture of the shoulder region requiring emergency management Incomplete or incorrectly completed questionnaire forms

The study population consists of adults aged 18-80 years with shoulder-related pain and/or functional limitation who were referred to or receiving care in physical therapy and rehabilitation units across multiple regions of Turkey. Participants represent a heterogeneous clinical spectrum of shoulder conditions, including rotator cuff-related disorders, adhesive capsulitis, traumatic shoulder lesions, and degenerative conditions. Individuals were recruited from multiple clinical centers to ensure diversity in demographic and clinical characteristics. All participants provided written and verbal informed consent prior to participation.