Applicability, validity, and reliability of the Piper Fatigue Scale in postpolio patients.

OBJECTIVE: To identify a scale that is potentially applicable for measuring the fatigue in postpolio patients and to evaluate its validity and reliability in this population.

DESIGN: Interview survey of 64 individuals with postpolio syndrome and 25 healthy controls of similar age range, with retest in a subset of postpolio patients. The sample was recruited from a postpolio support group, a postpolio clinic, and the general community. Subjects completed the Piper Fatigue Scale, the Beck Depression Inventory, and the Chalder Fatigue Questionnaire during the interview.

RESULTS: Face and content validity of the Piper Fatigue Scale was established by a team of experts and by a group of postpolio patients. The postpolio subjects had significantly higher Piper Fatigue Scale scores than the healthy control subjects (P < 0.001), demonstrating extreme groups validity. Convergent validity was shown with a strong positive correlation between Piper Fatigue Scale scores and Chalder Fatigue Questionnaire scores (r = 0.80). Reliability was also demonstrated with the Piper Fatigue Scale's high internal consistency (alpha = 0.98) and strong test-retest agreement (intraclass correlation coefficient = 0.98).

CONCLUSIONS: The Piper Fatigue Scale is a valid and reliable tool for measuring postpolio fatigue. This scale may be useful in other studies of postpolio fatigue, including those gauging the effectiveness of various treatments for this fatigue.