Article

Fatigue in post-polio syndrome (PPS) has been shown to affect quality
of life adversely. There is currently no disease-specific measure of fatigue for
PPS. OBJECTIVE: To develop a scale to measure fatigue in PPS that meets rigorous
psychometric standards. DESIGN: Qualitative followed by validation and
test-retest studies. SETTING: Polio clinic followed by national questionnaire
studies. PARTICIPANTS: A total of 45 participants from polio clinic for
qualitative; 319 participants from clinic or self-referral for validation study,
of whom 87 completed the retest questionnaire. METHODS: Draft questionnaire items
on PPS fatigue were derived from transcripts of qualitative interviews. After
cognitive debriefing, the draft measure was administered by mail along with
comparator questionnaires to a new sample. MAIN OUTCOME MEASUREMENTS: Draft PPS
fatigue measure, Fatigue Severity Scale, and visual analog scale for fatigue.
RESULTS: Analysis of 271 of 319 (85%) questionnaires identified a 2-factor
solution (RMSEA 0.058). For the physical subscale, a 20-item scale showed good
fit (chi(2)P = .189), strict unidimensionality (t-test 5.17%), and reliability
0.91. For the cognitive subscale, a 7-item scale showed excellent fit (chi(2)P =
.917), strict unidimensionality (t-test 5.2%), and reliability 0.89. Evidence of
a "difficulty factor" emerged also supporting a total score that showed good fit
(chi(2)P = .151), strict unidimensionality (t-test 0.4%), and reliability
consistent with group use at 0.73. Test-retest correlations for all scales were
greater than 0.85. Standard error of measurement on metric ranges was 5.4 for
total, 2.9 for physical, and 1.69 for cognitive domains. With the latent estimate
of the total score transformed to a 0-100 scale, the mean score was 49.5 (SD
6.9). Spearman correlations with the Fatigue Severity Scale and visual analog
scale were 0.60 and 0.55, respectively. CONCLUSIONS: A patient-derived
Neurological Fatigue Index for PPS, with physical and cognitive subscales and a
total score, has demonstrated good reliability, appropriate concurrent validity,
and satisfies the Rasch measurement model. A raw-score to interval scale
transformation is available for parametric applications and the calculation of
change scores. LEVEL OF EVIDENCE: III.
CI - Copyright (c) 2018 American Academy of Physical Medicine and Rehabilitation.
Published by Elsevier Inc. All rights reserved.

Langue : ANGLAIS