Measurement properties of the Western Ontario Shoulder Instability index in Dutch patients with shoulder instability.

Just A Van Der Linde,Loes W A H Van Beers,Derk A Van Kampen,Caroline B Terwee,Derek Fp Van Deurzen,W Jaap Willems

doi:10.1186/1471-2474-15-211

Abstract

BackgroundThe Western Ontario Shoulder Instability index (WOSI) is a patient-reported outcome measure for patients with shoulder instability. The purpose of this study was to validate the WOSI in a Dutch population by evaluating its structural validity, internal consistency, measurement error, reliability, and construct validity. Floor and ceiling effects were also addressed.MethodsTwo cohorts were recruited, including a total of 138 patients with shoulder instability. Confirmatory factor analysis was used to assess the structural validity and Cronbach’s α to assess internal consistency. The measurement error was calculated as the smallest detectable change (SDC). Reliability (test–retest) was estimated in a subgroup of 99 patients who completed the re-test after a mean of 13 days (5–30 days). Reliability was calculated with the intraclass correlation coefficient (ICC). Construct validity was evaluated by comparing the WOSI with the Oxford Shoulder Instability Score (OSIS), the Simple Shoulder Test, the Oxford Shoulder Score, the Disability of the Arm, Shoulder, and Hand assessment (DASH), and the Short Form-36 Health Survey. Measurement properties were evaluated for both the total WOSI score and its four domains.ResultsFactor analysis did not confirm the validity of the four domains. Best results were found for a one-factor model. Internal consistency was good, with Cronbach’s α ranging from 0.93 to 0.96. Reliability was excellent (ICC 0.88–0.92 for all subscales). The measurement error (SDC) was 23.0% for the total WOSI and 23% to 28% for the subscales (on a scale of 0–100). Regarding the construct validity, 76% of the results were in accordance with the hypotheses, including a high correlation with the OSIS (0.82) and DASH (0.81) assessments. No floor or ceiling effects were found.ConclusionThe Dutch version of WOSI showed good reliability and validity in a cohort of patients with shoulder instability, although the factor structure remains unclear.

Highlights

The Western Ontario Shoulder Instability index (WOSI) is a patient-reported outcome measure for patients with shoulder instability
The Western Ontario Shoulder Instability Index (WOSI) is a well-designed, thoroughly evaluated questionnaire that has proved to be reliable, valid, and sensitive to changes that are of clinical importance to Canadian patients with shoulder instability [7], leading to international acceptance
We evaluated its measurement properties according to the Consensus-based Standards for the Selection of Health Measurement Instruments (COSMIN) guidelines [16]

Summary

Introduction

The Western Ontario Shoulder Instability index (WOSI) is a patient-reported outcome measure for patients with shoulder instability. PROMs are designed to reflect the patient’s subjective function, addressing subdomains such as sports, work, and emotional well-being. They enable the practitioner to detect functional changes in a standardised way. The Western Ontario Shoulder Instability Index (WOSI) is a well-designed, thoroughly evaluated questionnaire that has proved to be reliable, valid, and sensitive to changes that are of clinical importance to Canadian patients with shoulder instability [7], leading to international acceptance. Translation and validation of PROMs allows comparison of national and international study results [7,16,17,18,19]

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