| MEASUREMENT PROPERTIES | |
| Limitations | |
| Observations |
The SASDAS has been validated against the ASDAS and other standard assessments in previously published manuscripts. These studies have shown that the SASDAS is highly correlated with the ASDAS and other measures of disease activity in AS patients. The SASDAS has also been shown to be a reliable and valid measure of disease activity in AS patients, with good internal consistency and responsiveness to changes in disease activity over time. However, the ASDAS has been shown to better discriminate between placebo and active treatment in AS patients. |
| 1. RELIABILITY | |
| A. Internal Consistency | Tested |
| Cronbach's (Describe) |
In a prospective validaion, SASDAS CRP but not ESR showed good internal consistency (Cronbach’s α 0.68 vs 0.18). |
| B. Reliability intraobserver or test-retest | Not Tested |
| Continuous scores: intraclass correlation coefficient (ICC) Dichotomus: Cohen kappa (Describe) |
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| 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 development study included consecutive patients with ankylosing spondylitis according to modified New York and/or Assessment in Ankylosing Spondylitis 2009 criteria. |
| B. Construct Validity: Structural validity |
Tested |
| Hypotheses-testing | Tested |
| Cross-cultural validity | Not Tested |
| Brief Description |
SASDAS correlated well with disease activity measures and with other classical measures in axSpA such as global pain and nocturnal pain, and BASFI. |
| C. Criterion validity | Tested |
| Comparison with a 'gold standard' Continuous scores: correlations, ROC curves Dichotomus: Sensitivity & Specificity (Describe) |
The cross-classification showed a significant overall agreement (defined as the percentage of observed exact agreements) for SASDAS vs ASDAS-ESR (weighted k = 0.704) and for SASDAS vs ASDAS-CRP (k = 0.661). .The BASDAI appears to be the less responsive (ES = 0.93 and SRM = 0.52). |