Initial psychometric evaluation of an upper extremity arthrogryposis multiplex congenita-specific measure using Rasch...

Area of Science:

• Pediatric Orthopedics
• Rehabilitation Medicine
• Outcome Measurement

Background:

• Arthrogryposis multiplex congenita (AMC) lacks specific upper extremity outcome measures for children.
• The SHAPE-UP (Shriners Hospitals Assessment of Performance and Participation in Upper Extremity) was developed for children aged 1-21 with AMC.
• It includes descriptive questions and video evaluation, divided into Task Completion and Analysis of Joint Motion and Position scales.

Purpose of the Study:

• To evaluate the psychometric properties of the SHAPE-UP Task Completion scale using Rasch analysis.
• To determine the correlation between the number of joints involved and the Task Completion score in children with AMC.

Main Methods:

• A cross-sectional study was conducted across six Shriners hospitals.
• One hundred and one participants with AMC completed the SHAPE-UP; 92 with upper limb involvement were analyzed.
• Rasch analysis was employed, and the scoring was revised to enhance model fit.

Main Results:

• Initial Rasch analysis indicated poor fit (significant item-trait interaction, disordered thresholds).
• Revisions, including collapsing scoring options and removing tasks, significantly improved model fit (p = 0.968).
• The revised scale demonstrated adequate content validity, achieved construct validity, and established excellent reliability (0.96130). A weak correlation (r = -0.0466) was found between joints involved and task completion.

Conclusions:

• The revised SHAPE-UP Task Completion scale aligns with Rasch model expectations.
• Further clinical interpretation is needed for the Analysis of Joint Motion and Position scale.
• Future research should investigate the reliability, validity, and responsiveness of the complete SHAPE-UP measure.