| MEASUREMENT PROPERTIES | |
| Limitations | >=5 European languages (English) |
| Observations | |
| 1. RELIABILITY | |
| A. Internal Consistency | Tested |
| Cronbach's (Describe) |
Cronbach’s alpha: 0.89–0.94 in SLE. In the mFSS version, Cronbach’s alpha=0.95 in both PsA and SLE. |
| B. Reliability intraobserver or test-retest | Tested |
| Continuous scores: intraclass correlation coefficient (ICC) Dichotomus: Cohen kappa (Describe) |
There were no significant differences between test and retest in the separate items or in the total FSS scores. The median of the weighted kappa coefficients was 0.75 (range 0.47–0.91) and the weighted kappa coefficient for the sum score was 0.74 |
| C. Reliability interobserver or Measurement error | Not Tested |
| Standard error of measurement (SEM), smallest detectable change (SDC) or Limits of agreement (LoA) (Describe) |
|
| 2. VALIDITY | |
| A. Content validity: face validity | Not Tested |
| Expert opinion (relevance and comprehensiveness) (Describe) |
It is not stated where the 28 items originated from or whether patients were involved in their development. |
| B. Construct Validity: Structural validity |
Tested |
| Hypotheses-testing | Tested |
| Cross-cultural validity | Tested |
| Brief Description |
Factor analysis was performed on 28 draft items, and identified 9 items common to both SLE and MS. |
| C. Criterion validity | Tested |
| Comparison with a 'gold standard' Continuous scores: correlations, ROC curves Dichotomus: Sensitivity & Specificity (Describe) |
Correlation with Short Form 36 vitality subscale (SF-36 VT): -0.56 to -0.63 in SLE, OA, and RA. mFSS correlated strongly with a fatigue visual analog scale in SLE (r= 0.81) and with Functional Assessment Chronic Illness Therapy (Fatigue) in patients with PsA (r= -0.79). |