| MEASUREMENT PROPERTIES | |
| Limitations | English only |
| Observations |
No translation needed. |
| 1. RELIABILITY | |
| A. Internal Consistency | Tested |
| Cronbach's (Describe) |
Cronbach’s alpha for the CDAI was 0.833 |
| B. Reliability intraobserver or test-retest | Tested |
| Continuous scores: intraclass correlation coefficient (ICC) Dichotomus: Cohen kappa (Describe) |
When repeated testing 1 week apart was performed, ICC values were 0.89 for the CDAI. |
| C. Reliability interobserver or Measurement error | Not Tested |
| Standard error of measurement (SEM), smallest detectable change (SDC) or Limits of agreement (LoA) (Describe) |
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| 2. VALIDITY | |
| A. Content validity: face validity | Tested |
| Expert opinion (relevance and comprehensiveness) (Describe) |
The CDAI 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 |
Tested |
| Hypotheses-testing | Tested |
| Cross-cultural validity | Tested |
| Brief Description |
The contribution of CRP in the SDAI was shown to be low (about 5%) and thus authors excluded CRP from the SDAI, developing the CDAI. Pearson correlation analysis between SDAI and CDAI in an inception cohort (n = 91 patients) and in a cross-sectional routine cohort correlated almost perfectly. |
| C. Criterion validity | Tested |
| Comparison with a 'gold standard' Continuous scores: correlations, ROC curves Dichotomus: Sensitivity & Specificity (Describe) |
Gold standard was DAS28. Linear regression analysis showed a significant correlation between DAS28 and CDAI (R2 =0.873; p<0.0001). The ROC curves to discriminate between patients categorized by each criteria of disease activity, i.e. remission and/or low disease activity criteria and by moderate and/or high disease activity criteria in the 2 models with the DAS28 and CDAI indices were similar. The discriminatory power of both indices was good, without significant difference, with an AUC of 0.904 (95% CI 0.893±0.915) for DAS28, and 0.899 (95% CI 0.877±0.901) for CDAI. |