Abstract Details

Title Construct Validity of the 10-meter Walk/Run Test to Assess Motor Impairment in Patients with Alexander Disease

Topic Child Neurology and Developmental Neurology

Presentation(s) P2 - Poster Session 2 (11:45 AM-12:45 PM)

Poster/Presentation
Number 8-004

Objective To evaluate construct validity of the 10-meter walk/run test (10MWRT) to capture motor impairments in patients with Alexander disease (AxD).

Background There are no validated outcome measures to capture motor impairments in patients with AxD, a rare progressive astrocytopathy.

Design/Methods Patients with clinical and radiographic features of AxD, confirmed by a pathologic variant in GFAP, were enrolled in a natural history study with data collected by physical and occupational therapists using standardized testing. Clinical outcome assessments included 10MWRT, Gross Motor Function Measure-88 (GMFM-88), Peabody Developmental Motor Scales-2 (PDMS-2), Berg Balance Scale (BBS), Pediatric Balance Scale (PBS), Gross Motor Function Classification System Expanded and Revised (GMFCS-ER), and Manual Ability Classification System (MACS). For 10MWRT (but not GMFM-88), orthoses or assistive devices were allowed. For 10MWRT, patients were instructed to walk or run as fast as possible from start line to finish line. Time was recorded for three trials. Construct validity was evaluated by strength of associations between the fastest of three 10MWRT trials and concurrent GMFM-88 (walking domain and total score), PDMS-2 Gross Motor Score, PBS, and BBS (convergent validity), and GMFCS-ER and MACS (known-groups validity). Pearson correlations (convergent validity) and numeric mean differences (known-groups validity) assessed associations among measures at first visit with 10MWRT completed.

Results Thirty patients (13 females; mean [SD] age 16.5 [15.3] years, range 2.2-54.8) completed 10MWRT. Fastest 10MWRT time correlated strongly with GMFM-88 (Domain E: r=-0.68, Total: r=-0.76), PDMS-2 Gross Motor Score (<6 years old only, n=5, r=-0.94), and BBS (>13 years, n=14, r=-0.82) or PBS (<13 years, n=12, r=-0.90). Stepwise numeric increases in mean 10MWRT rates were observed with greater impairments on GMFCS and MACS. Sensitivity analyses using all available 10MWRT assessments to date supported primary analyses.

Conclusions Data support 10MWRT as a construct valid measure to capture motor function in patients with AxD.

Authors/Disclosures
Aaron Yarlas, PhD (Ionis Pharmaceuticals) PRESENTER	Dr. Yarlas has received personal compensation for serving as an employee of Ionis Pharmaceuticals. Dr. Yarlas has stock in Ionis Pharmaceuticals.
Ann Harrington (Children's Hospital of Philadelphia)	No disclosure on file
Tracy Kornafel	Tracy Kornafel has nothing to disclose.
Elizabeth Ballance	No disclosure on file
Kimberly Kopin	No disclosure on file
Samuel Pierce	Samuel Pierce has nothing to disclose.
Joshua Joung, Other (Children's Hospital of Philadelphia)	Mr. Joung has nothing to disclose.
Kathryn Gallison, Other (The Children's Hospital of Philadelphia)	The institution of Miss Gallison has received research support from Ionis Pharmaceuticals.
Geraldine Liu (Children’s Hospital of Philadelphia)	An immediate family member of Geraldine Liu has received personal compensation in the range of $10,000-$49,999 for serving as an Expert Witness for Various. An immediate family member of Geraldine Liu has received publishing royalties from a publication relating to health care.
Walter Faig	Walter Faig has received personal compensation for serving as an employee of Westat.
Abigail E. Collins, MD (Ionis Pharmaceuticals)	Dr. Collins has received personal compensation for serving as an employee of Ionis Pharmaceuticals. Dr. Collins has stock in Ionis Pharmaceuticals.
Amy T. Waldman, MD (Children's Hospital of Philadelphia)	Dr. Waldman has received personal compensation in the range of $10,000-$49,999 for serving on a Scientific Advisory or Data Safety Monitoring board for SwanBio. An immediate family member of Dr. Waldman has or had stock in Pfizer. The institution of Dr. Waldman has received research support from Ionis Pharmaceuticals. The institution of Dr. Waldman has received research support from Roche/Genentech. The institution of Dr. Waldman has received research support from Ionis Pharmaceuticals. The institution of Dr. Waldman has received research support from Calico. Dr. Waldman has received publishing royalties from a publication relating to health care. Dr. Waldman has received publishing royalties from a publication relating to health care.

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