The Functional Assessment of Chronic Illness Therapy-Fatigue scale is a reliable and valid instrument for measuring fatigue in patients with psoriatic arthritis, a study has found.
One of a number of self-reported scales used to measure fatigue in patients with arthritis, the Functional Assessment of Chronic Illness Therapy (FACIT)-Fatigue scale has garnered interest in rheumatologic drug trials for its capacity to demonstrate decreases in fatigue associated with pharmacotherapy, according to Dr. Vinod Chandron of Toronto Western Hospital, and colleagues. Although the measure has demonstrated promise in clinical trials, it has not been validated in patients with psoriatic arthritis specifically, the authors wrote. Therefore, the investigators enrolled 135 consecutive patients from the University of Toronto psoriatic arthritis clinic in a study designed to determine the internal consistency, test-retest reliability, criterion, and construct validity of the FACIT-Fatigue scale in this population (Ann. Rheum. Dis. 2007 Feb. 26 [Epub doi:10.1136/ard.2006.065763]).
All study patients underwent a standardized clinical assessment including complete history, physical examination, and laboratory evaluation, Dr. Chandron and investigators reported. Laboratory testing included hemoglobin measurement and erythrocyte sedimentation rate (ESR).
The patients were asked to complete the FACIT-Fatigue questionnaire at the clinic and again 1 week later to assess test-retest reliability using the intraclass correlation coefficient (ICC). They also were asked to complete the Modified Fatigue Severity Scale (mFSS) to evaluate the construct validity of the FACIT-Fatigue measure.
Among the 80 men and 55 women (mean age 52 years) in the investigation, the mean disease duration was 17 years; the mean Psoriasis Area Severity Index score was 3.5, with the mean counts for actively inflamed, swollen, and clinically damaged joints being 4.5, 1.3, and 8.7, respectively. Of the 135 patients, 16 met the clinical criteria for fibromyalgia, 27 had anemia, 63 had elevated ESR levels, and 26 had overwhelming fatigue. The mean FACIT-Fatigue score in the study population was 35.8 out of a possible 52, according to the investigators.
More than half of the patients (54%) returned the repeat questionnaires. There was no difference in disease characteristics between those who did and did not return the questionnaires, the authors reported. The ICC between first and repeat scores was high, at 0.95. Additionally, the Cronbach's alpha of the 13 FACIT-Fatigue items was 0.96, indicating a high level of internal consistency.
The correlation between the FACIT-Fatigue and the mFSS was high, at −0.79. “The negative sign reflects the fact that higher scores in the FACIT-Fatigue indicate less fatigue whereas higher scores in the mFSS indicated more fatigue,” the investigators explained. The FACIT-Fatigue scores also correlated with actively inflamed joint count and swollen joint count but not with clinically damaged joint count, the authors observed. There were no differences in the FACIT-Fatigue scores between patients with and without elevated ESR or anemia, and males and females scored similarly.
Among patients reporting overwhelming fatigue, the FACIT-Fatigue scores were lower, meaning more fatigue, compared with those who did not report overwhelming fatigue, the authors stated.