Validation of the Functional Assessment of Chronic Illness Therapy Fatigue Scale relative to other instrumentation in patients with rheumatoid arthritis.

OBJECTIVE

This study validated a brief measure of fatigue in rheumatoid arthritis (RA), the Functional Assessment of Chronic Illness Therapy (FACIT) Fatigue Scale.

METHODS

The FACIT Fatigue was tested along with measures previously validated in RA: the Multidimensional Assessment of Fatigue (MAF) and Medical Outcomes Study Short-Form 36 (SF-36) Vitality. The sample included 636 patients with RA enrolled in a 24 week double blind, randomized clinical trial (RCT) of adalimumab versus placebo.

RESULTS

The FACIT Fatigue showed good internal consistency (alpha = 0.86 to 0.87), strong association with SF-36 Vitality (r = 0.73 to 0.84) and MAF (r = -0.84 to -0.88), and the ability to differentiate patients according to clinical change using the American College of Rheumatology (ACR) response criteria (ACR 20/50/70). Psychometric performance of the FACIT Fatigue scale was comparable to that of the other 2 fatigue measures. A minimally important difference in FACIT Fatigue change score of 3-4 points was confirmed in a separate sample of 271 patients with RA enrolled in a second double blind RCT of adalimumab versus placebo.

CONCLUSION

The FACIT Fatigue is a brief, valid measure for monitoring this important symptom and its effects on patients with RA.