| MEASUREMENT PROPERTIES | |
| Limitations | >=5 European languages (English) |
| Observations | |
| 1. RELIABILITY | |
| A. Internal Consistency | Tested |
| Cronbach's (Describe) |
Cronbach’s α = 0.93 |
| B. Reliability intraobserver or test-retest | Tested |
| Continuous scores: intraclass correlation coefficient (ICC) Dichotomus: Cohen kappa (Describe) |
ICC (95% CI) = 0.90 (0.84 to 0.94) |
| C. Reliability interobserver or Measurement error | Tested |
| Standard error of measurement (SEM), smallest detectable change (SDC) or Limits of agreement (LoA) (Describe) |
The smallest detectable difference (SDD) = 1.8 The smallest detectable change (SDC) = 1.3 |
| 2. VALIDITY | |
| A. Content validity: face validity | Tested |
| Expert opinion (relevance and comprehensiveness) (Describe) |
Ten patients identified 17 domains or areas of health relevant for inclusion in the score, then 96 patients (from 10 European countries) ranked these domains in order of decreasing importance. The seven most important domains were selected. Instruments were chosen for each domain after extensive literature research of psychometric properties and expert opinion. |
| B. Construct Validity: Structural validity |
Tested |
| Hypotheses-testing | Tested |
| Cross-cultural validity | Tested |
| Brief Description |
Data from the weighting process were used to analyse weights across demographic and disease characteristics. Weights were analysed as binary measures (dichotomised by median). By multiple component analysis, demographic (age, sex, disease duration) and activity/severity data (pain VAS, HAQ, fatigue VAS, global assessment VAS, SF36) were projected on the axes created based on dichotomised weights to assess potential relationships. The first three axes contributed 68.6% to the total inertia. The domains that most contributed to the construction of axis 1 and which were best and similarly represented by that axis were pain and emotional well-being. A high score allocated to emotional well-being appeared to be associated with a higher score for pain. The variables that most contributed to the construction of axis 2 were functional disability, sleep and fatigue, the first two domains being best represented by axis 2. It appeared that higher scores for function were related to lower scores for the other two domains and vice versa. Physical wellbeing and sleep contributed most to the construction of axis 3. A total of 671 patients with RA with features of established disease were analysed, 563 and 108 from RAID and Rainbow, respectively. The NRS correlated moderately to strongly with the respective external instrument of reference (r=0.62-0.81). Reliability ranged from 0.64 (0.51-0.74) (pain) to 0.83 (0.76-0.88) (sleep disturbance) and responsiveness from 0.93 (0.73-1.13) (sleep disturbance) to 1.34 (1.01-1.64) (pain). |
| C. Criterion validity | Not Tested |
| Comparison with a 'gold standard' Continuous scores: correlations, ROC curves Dichotomus: Sensitivity & Specificity (Describe) |
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