| MEASUREMENT PROPERTIES | |
| Limitations | >=5 European languages (English) |
| Observations | |
| 1. RELIABILITY | |
| A. Internal Consistency | Tested |
| Cronbach's (Describe) |
In 229 patients with RA, Cronbach’s α was 0.93 for total fatigue, 0.71 for physical fatigue, 0.91 for living with fatigue, 0.92 for cognitive fatigue, and 0.89 for emotional fatigue; all except one were excellent values. The correlations between total fatigue and the four subscales range from r = 0.75 to 0.88 (all very good to excellent). |
| B. Reliability intraobserver or test-retest | Tested |
| Continuous scores: intraclass correlation coefficient (ICC) Dichotomus: Cohen kappa (Describe) |
The test-retest was performed 1 to 2 hours apart (n = 50 patients with RA before and after clinic visits); correlations were excellent overall; for total fatigue r = 0.95, for physical fatigue r = 0.94, for living with fatigue r = 0.89, for cognitive fatigue r = 0.89, and for emotional fatigue r = 0.92. |
| C. Reliability interobserver or Measurement error | Tested |
| Standard error of measurement (SEM), smallest detectable change (SDC) or Limits of agreement (LoA) (Describe) |
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| 2. VALIDITY | |
| A. Content validity: face validity | Tested |
| Expert opinion (relevance and comprehensiveness) (Describe) |
The items and their wording cover a range of severity and impact of fatigue and were derived from patient interviews, which were then refined with focus groups. |
| B. Construct Validity: Structural validity |
Not Tested |
| Hypotheses-testing | Tested |
| Cross-cultural validity | Tested |
| Brief Description | |
| C. Criterion validity | Tested |
| Comparison with a 'gold standard' Continuous scores: correlations, ROC curves Dichotomus: Sensitivity & Specificity (Describe) |
Total fatigue correlated very strongly with the MAF (specific to RA) at 0.82 and with the FACIT-F at −0.81 and positively with the SF-36 VT at −0.64. A range of moderate to strong correlations was also observed between these measures and the BRAF subscales: physical fatigue (severity) −0.68 to 0.83, living with fatigue −0.54 to −0.74, emotional fatigue −0.50 to 0.66, and cognitive fatigue −0.40 to 0.55. The lower levels of association observed in cognitive fatigue may reflect the lack of elements of cognitive fatigue in other fatigue measures. For total fatigue and all subscales, the correlation with SF-36 VT was weaker than with other fatigue scales (see Short Form 36 Vitality). |