| MEASUREMENT PROPERTIES | |
| Limitations | >=5 European languages (English) |
| Observations | |
| 1. RELIABILITY | |
| A. Internal Consistency | Tested |
| Cronbach's (Describe) |
Cronbach's alpha for the DAS28 in RA patients was 0.733 |
| B. Reliability intraobserver or test-retest | Tested |
| Continuous scores: intraclass correlation coefficient (ICC) Dichotomus: Cohen kappa (Describe) |
ICC=0.92 |
| C. Reliability interobserver or Measurement error | Tested |
| Standard error of measurement (SEM), smallest detectable change (SDC) or Limits of agreement (LoA) (Describe) |
SDD as percentage of mean value of the outcome = 23.2 % |
| 2. VALIDITY | |
| A. Content validity: face validity | Tested |
| Expert opinion (relevance and comprehensiveness) (Describe) |
The DAS28 includes variables from the ACR core set of measures used to assess outcomes in RA. No measures of disability or joint damage are included. |
| B. Construct Validity: Structural validity |
Not Tested |
| Hypotheses-testing | Tested |
| Cross-cultural validity | Not Tested |
| Brief Description | |
| C. Criterion validity | Tested |
| Comparison with a 'gold standard' Continuous scores: correlations, ROC curves Dichotomus: Sensitivity & Specificity (Describe) |
Regression analysis showed no significant differences between a physician’s and patient’s joint counts and DAS. There were middle to high correlations between patient and physician assessments of tender joints and swollen joints; using R2, this explained 70% of the variance for tender joints and 40% for swollen joints. Kappa analysis showed good agreement between physician and patient assessments of individual joint tenderness (kappa values 0.49–0.84). There was lower agreement for individual swollen joints (kappa values 0.02–0.61). |