Original article
Reliability, validity, and responsiveness of the simple shoulder test: Psychometric properties by age and injury type

https://doi.org/10.1016/j.jse.2006.07.003Get rights and content

The purpose of this study was to measure the reliability, validity, and responsiveness of the Simple Shoulder Test (SST) scale and to examine these in patients stratified by age and injury type. Test-retest reliability, content validity, criterion validity, construct validity, and responsiveness were determined for the SST. The study population comprised 1077 patients with shoulder instability and rotator cuff injuries, ranging in age from 14 to 85 years. The SST demonstrated acceptable test-retest reliability (intraclass correlation coefficient >0.90) and content validity (floor and ceiling effects <10%). Correlations with the physical functioning component of the Short Form 12 were significant (r = 0.439, P < .05); however, the correlations were not significant when stratified by age group (>60 years) (r = 0.271, P = .349) and injury type (rotator cuff injury) (r = 0.337, P = .085). Correlations with the American Shoulder and Elbow Surgeons were also significant (r = 0.807, P < .001). The construct validity of the SST was acceptable, with all 8 hypotheses demonstrating significance (P < .05). The SST was responsive to change (effect size, 0.81; standardized response mean, 0.81). However, there were differences after stratification for age group and injury type. The SST demonstrated overall acceptable psychometric performance; however, differences were found when data were stratified by age and injury type.

Section snippets

Methods

The clinical records used in this analysis were collected on patients between 1992 and 2004. A modified SST was administered routinely to all patients with shoulder complaints during their initial visit to the clinic and, in many instances, on subsequent visits to the clinic.

Results

The mean SST score was 6.86 (SD, 3.47). The mean scores for the age groups and injury type are listed in Table II. A 2-way analysis of variance was applied to determine whether SST scores differed by age group and injury type (Figure 1). There was a main effect of age group, after collapsing for injury type, as SST scores decreased with an increase in age (P = .011). There was not a main effect of injury type after collapsing across age group (P = .480). There was not a significant interaction

Discussion

This study provides additional information regarding the reliability, validity, and responsiveness of the SST. In this cohort of patients with shoulder injuries, there was strong test-retest reliability. The SST correlated well with the gold standard, the SF-12, for physical function and the ASES scale; fewer than 10% of patients had either the lowest possible score (floor effects) or the highest possible score (ceiling effects); and the SST performed well with regard to a priori hypotheses.

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