| MEASUREMENT PROPERTIES | |
| Limitations | <5 European languages (English) |
| Observations | |
| 1. RELIABILITY | |
| A. Internal Consistency | Tested |
| Cronbach's (Describe) |
Cronbach’s α for the 8 domains: 0.88-0.96 |
| B. Reliability intraobserver or test-retest | Tested |
| Continuous scores: intraclass correlation coefficient (ICC) Dichotomus: Cohen kappa (Describe) |
ICC over 4 weeks for each domain ranged from 0.72 to 0.93 |
| 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 | Tested |
| Expert opinion (relevance and comprehensiveness) (Describe) |
The content was derived from semi structured interviews with patients and psychometric testing with patient’s feedback. A panel of discussant met to consider each item in terms of association with SLE activity, generality and expression of a single idea. |
| B. Construct Validity: Structural validity |
Not Tested |
| Hypotheses-testing | Tested |
| Cross-cultural validity | Tested |
| Brief Description |
It was evaluated if the instrument can differentiate between patients with different degrees of disease severity according to BILAG (disease activity in 4 groups) and the SDI (damage yes/no) |
| C. Criterion validity | Tested |
| Comparison with a 'gold standard' Continuous scores: correlations, ROC curves Dichotomus: Sensitivity & Specificity (Describe) |
Comparing with an established questionnaire to measure the same construct: SF-36 Spearman correlation: 0.71-0.79 for the 4 comparable domains |