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Research Article  |   July 2003
Test–Retest Reliability and Convergent Validity of the Fatigue Impact Scale for Persons With Multiple Sclerosis
Author Affiliations
  • Virgil Mathiowetz, PhD, OTR, FAOTA, is Associate Professor, Program in Occupational Therapy, Department of Physical Medicine & Rehabilitation, University of Minnesota, MMC 388, 420 Delaware Street SE, Minneapolis, Minnesota 55455; mathi003@umn.edu
Article Information
Multiple Sclerosis / Neurologic Conditions / Assessment: Function and the Environment
Research Article   |   July 2003
Test–Retest Reliability and Convergent Validity of the Fatigue Impact Scale for Persons With Multiple Sclerosis
American Journal of Occupational Therapy, July/August 2003, Vol. 57, 389-395. doi:10.5014/ajot.57.4.389
American Journal of Occupational Therapy, July/August 2003, Vol. 57, 389-395. doi:10.5014/ajot.57.4.389
Abstract

OBJECTIVE. The test–retest reliability and the convergent validity of the Fatigue Impact Scale (FIS) were evaluated using secondary data from 54 persons with multiple sclerosis (MS).

METHODS. This reliability and validity study used FIS data from before and after two control periods to evaluate test–retest reliability. Convergent validity of the FIS with the Fatigue Severity Scale and with subscales of the SF-36 Health Survey was evaluated using data collected before the first control period.

RESULTS. No significant differences between before and after FIS measurements and intraclass correlation coefficients ranging from .68 to .85 indicate that the FIS has good test–retest reliability except for the physical subscale. The expected moderate correlations between the FIS and several subscales of the SF-36 support its convergent validity. In contrast, the unexpected low correlation between the FIS and Fatigue Severity Scale does not support convergent validity.

CONCLUSION. The FIS has adequate reliability and validity and is recommended to evaluate the effectiveness of fatigue management interventions such as energy conservation education for persons with MS.