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Psychometric properties of functional mobility outcome measures in children with arthrogryposis multiplex congenita
Ahlam Zidan1,2, Laurie Snider1, Emmanouil Rampakakis1,3
1Faculty of Medicine and Health Sciences, McGill University, Montreal, Quebec, Canada.
Insights
This study validates mobility measures for children with arthrogryposis multiplex congenita (AMC). The findings establish reliable benchmarks for assessing functional mobility in this population.
Area of Science:
- Pediatric Rehabilitation
- Orthopedics
- Movement Science
Background:
- Arthrogryposis multiplex congenita (AMC) is a rare neuromuscular condition affecting joint mobility.
- Accurate assessment of functional mobility is crucial for guiding interventions in children with AMC.
- Existing mobility measures require validation for construct validity, agreement, and minimal important difference (MID) in the AMC population.
Purpose of the Study:
- To establish the construct validity, agreement, and MID of commonly used mobility measures in children with AMC.
- To provide evidence-based benchmarks for clinicians and researchers assessing mobility in AMC.
- To compare the performance of the Functional Mobility Scale (FMS), Gillette Functional Assessment Questionnaire (FAQ), Functional Independence Measure for Children (WeeFIM), and Patient-Reported Outcomes Measurement Information System (PROMIS).
Main Methods:
- A cohort of 248 children with AMC (mean age 10 years 10 months) was assessed.
- Convergent, discriminant, and known-groups validity were evaluated using correlation and ANOVA.
- Agreement was assessed using Cohen's kappa, and MIDs were estimated using distribution-based methods.
Main Results:
- All four mobility measures demonstrated robust convergent and discriminant validity.
- Significant differences in mobility were observed across AMC subtypes, supporting known-groups validity.
- Weak to good agreement was found, with established MIDs for FMS (1 level), FAQ (2 levels), PROMIS (3.19-4.34), and WeeFIM (14.24).
Conclusions:
- The validated mobility measures offer reliable tools for assessing functional mobility in children with AMC.
- Established construct validity, agreement, and MIDs provide essential benchmarks for clinical practice and research.
- These findings support the use of FMS, FAQ, WeeFIM, and PROMIS for evidence-based mobility assessment in pediatric AMC.
Aim:
To establish the construct validity, agreement, and minimal important difference (MID) of widely used mobility measures in arthrogryposis multiplex congenita (AMC).
Method:
Participants (n = 248, 126 males, mean age 10 years 10 months, standard deviation 3 years 11 months) with AMC were assessed using the Functional Mobility Scale (FMS), Gillette Functional Assessment Questionnaire (FAQ), Functional Independence Measure for Children (WeeFIM), and Patient-Reported Outcomes Measurement Information System (PROMIS). Convergent and discriminant validity were evaluated using Spearman's rank correlations, while known-groups validity was examined using analysis of variance. Cohen's kappa and distribution-based methods were used to estimate agreement and MIDs respectively.
Results:
Robust convergent (ρ = 0.66-0.82, 95% confidence interval [CI] 0.54-0.86) and discriminant (ρ = 0.06-0.31, 95% CI -0.11 to 0.43) validity were found for all four mobility measures. Known-groups validity was supported by significant mean differences across AMC subtypes (amyoplasia, distal arthrogryposis, central nervous system/syndromic; p < 0.001). The measures also showed weak to good agreement in classifying mobility. A difference of one and two levels on the FMS and FAQ respectively, was found to be minimally important. For the PROMIS and WeeFIM, estimated MID values were 3.19 to 4.34 and 14.24 respectively.
Interpretation:
The robust construct validity, agreement, and MIDs provide clinicians and researchers with evidence-based benchmarks for assessing mobility in children with AMC.
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