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Reliability and Validity of the 6-Minute Walk Test in Hypophosphatasia
Dawn Phillips1, Ioannis C Tomazos2, Scott Moseley2
1Division of Physical Therapy Department of Allied Health Sciences University of North Carolina Chapel Hill NC USA.
Insights
The 6-Minute Walk Test (6MWT) is a reliable and valid measure of physical function in pediatric patients with hypophosphatasia (HPP). This test accurately assesses mobility and disease severity across children, adolescents, and adults with HPP.
Area of Science:
- Pediatric Endocrinology
- Bone and Mineral Metabolism
- Clinical Outcome Measures
Background:
- Hypophosphatasia (HPP) is a rare metabolic bone disease affecting skeletal development and integrity.
- Accurate assessment of physical function is crucial for monitoring disease progression and treatment efficacy in pediatric HPP.
- The 6-Minute Walk Test (6MWT) is a commonly used measure of functional capacity, but its utility in pediatric HPP requires validation.
Purpose of the Study:
- To evaluate the reliability and validity of the 6-Minute Walk Test (6MWT) in patients diagnosed with pediatric hypophosphatasia (HPP).
- To establish minimal clinically important differences for the 6MWT in different age groups within the pediatric HPP population.
- To assess the correlation of 6MWT performance with skeletal disease severity and other functional measures in pediatric HPP.
Main Methods:
- The 6MWT was administered to children, adolescents, and adults with HPP at screening and baseline in two clinical studies of asfotase alfa.
- Test-retest reliability was assessed using Pearson's correlation coefficients.
- Minimal clinically important differences were estimated using distribution-based methods. Correlations with skeletal disease measures, functional status, and pain were analyzed.
Main Results:
- The 6MWT demonstrated high test-retest reliability across all age groups (children: r=0.95, adolescents: r=0.81, adults: r=0.94).
- Significant correlations were found between 6MWT distance and measures of skeletal disease severity, disability, daily functioning, and pain.
- Minimal clinically important differences were determined to be 31m for children/adults and 43m for adolescents.
Conclusions:
- The 6-Minute Walk Test (6MWT) is a reliable and valid instrument for assessing physical functioning in pediatric hypophosphatasia (HPP) patients.
- The 6MWT provides meaningful data that correlates with disease severity and functional impact in this population.
- These findings support the use of the 6MWT as a key outcome measure in clinical trials and management of pediatric HPP.
Abstract:
This investigation evaluated the reliability and validity of the 6-Minute Walk Test (6MWT) in patients with pediatric hypophosphatasia (HPP). Children (aged 6 to 12 years; n = 11), adolescents (13 to 17 years; n = 4), and adults (18 to 65 years; n = 9) completed the 6MWT at screening and baseline in two clinical studies of asfotase alfa. Test-retest reliability of the 6MWT, evaluated with Pearson's correlation coefficients (r) for screening versus baseline, was high for children (r = 0.95; p < 0.0001), adolescents (r = 0.81; p = 0.125), and adults (r = 0.94; p = 0.0001). The most conservative minimal clinically important differences, estimated using distribution-based methods, were 31 m (children and adults) and 43 m (adolescents). In children, the 6MWT correlated significantly with scores on measures of skeletal disease, which included the Radiographic Global Impression of Change scale (r = 0.50; p < 0.0001) and the Rickets Severity Scale (r = -0.78; p < 0.0001), such that distance walked increased as the severity of skeletal disease decreased. Significant (p < 0.0001) correlations with the 6MWT distance walked were also observed for children with scores on parent-reported measures of disability (r = -0.67), ability to function in activities of daily living (r = 0.71 to 0.77), and parent-reported measures of pain (r = -0.39). In adolescents and adults, 6MWT distance walked correlated significantly (p < 0.05) with measures of lower extremity function (r = 0.83 and 0.60, respectively), total pain severity (r = -0.41 and -0.36, respectively), and total pain interference (r = -0.41 and -0.49, respectively). Collectively, these data indicate that the 6MWT is a reliable, valid measure of physical functioning in patients with pediatric HPP. © 2018 The Authors. JBMR Plus Published by Wiley Periodicals, Inc. on behalf of the American Society for Bone and Mineral Research.
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