| MEASUREMENT PROPERTIES | |
| Limitations | >=5 European languages (English) |
| Observations | |
| 1. RELIABILITY | |
| A. Internal Consistency | Tested |
| Cronbach's (Describe) |
Internal consistency was demonstrated on the basis of fair agreement between the SDAI and the DAS28 (κ = 0.382). |
| B. Reliability intraobserver or test-retest | Tested |
| Continuous scores: intraclass correlation coefficient (ICC) Dichotomus: Cohen kappa (Describe) |
A joint count was performed two times 1 week apart by the patient and by an experienced physician. Test-retest reliability was expressed as the least significant difference (LSD), as the LSD in percent of the mean score (%LSD): 8.3 and 59.9. |
| 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= 59.9 % |
| 2. VALIDITY | |
| A. Content validity: face validity | Tested |
| Expert opinion (relevance and comprehensiveness) (Describe) |
The SDAI includes variables from the American College of Rheumatology (ACR) core set of measures used to assess outcomes in RA. No measures of disability or joint damage are included. The SDAI was evaluated using a survey of patient profiles among 21 rheumatologists that showed excellent agreement with the physician's ratings of the patients' disease activity. |
| 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) |
There was no significant difference in the percentage of patients in remission according to the self-derived SDAI (14.5%) and the physician-derived SDAI (11.6%) (P = 0.172). |