Validity and reliability of physical activity measures in multiple sclerosis.

Area of Science:

• Rehabilitation science
• Biomedical engineering
• Clinical measurement

Background:

• Accurate measurement of physical activity is crucial for managing multiple sclerosis (MS).
• Objective measures are needed to complement subjective self-reports in persons with MS (PwMS).
• Evaluating the psychometric properties of wearable sensors and questionnaires is essential for reliable data collection.

Purpose of the Study:

• To evaluate the psychometric properties of physical activity measures in persons with multiple sclerosis (PwMS).
• To compare the validity and reliability of different accelerometers and a questionnaire for assessing physical activity in PwMS.

Main Methods:

• Adults with MS (n=30 for validation, n=57 for test-retest) participated.
• Steps were measured using PiezoRX, Yamax SW200, and ActiGraph GT9X Link (AGlink).
• Time in different positions was measured with AGlink, validated against video analysis; the Physical Activity and Disability Survey - Revised Swedish version (PADS-R(Sw)) was also evaluated.

Main Results:

• AGlink (low-frequency extension filter) and PiezoRX demonstrated high validity for step measurement (MeAPE 0.9-3.3%).
• Yamax SW200 and AGlink (normal filter/display) showed lower validity.
• AGlink was not valid for measuring sitting or lying down; PADS-R(Sw) showed moderate correlation with AGlink steps (r=0.492) and high relative reliability (ICC=0.85).

Conclusions:

• ActiGraph GT9X Link (AGlink) and PiezoRX are valid devices for measuring steps in persons with multiple sclerosis.
• The Physical Activity and Disability Survey - Revised Swedish version (PADS-R(Sw)) is a valid questionnaire with good relative reliability, but its absolute reliability is insufficient for clinical use.