| MEASUREMENT PROPERTIES | |
| Limitations | |
| Observations | |
| 1. RELIABILITY | |
| A. Internal Consistency | Not Tested |
| Cronbach's (Describe) | |
| B. Reliability intraobserver or test-retest | Not Tested |
| Continuous scores: intraclass correlation coefficient (ICC) Dichotomus: Cohen kappa (Describe) |
Although individual components of the index have been subjected to reliability studies, further work is needed using the index itself. |
| C. Reliability interobserver or Measurement error | Tested |
| Standard error of measurement (SEM), smallest detectable change (SDC) or Limits of agreement (LoA) (Describe) |
Measurement error for PASDAS was estimated at 0.8. |
| 2. VALIDITY | |
| A. Content validity: face validity | Not Tested |
| Expert opinion (relevance and comprehensiveness) (Describe) |
The PASDAS was developed as part of an international Group for Research and Assessment of Psoriasis and Psoriatic Arthritis (GRAPPA) exercise |
| B. Construct Validity: Structural validity |
Tested |
| Hypotheses-testing | Not Tested |
| Cross-cultural validity | Not Tested |
| Brief Description |
PCA revealed seven components which approximated to the following domains: patient-reported measures (excluding mental component summary score (MCS) of the Medical Outcomes Survey Short form-36 (SF-36)), skin, peripheral joint counts, dactylitis, enthesitis, acute phase response and SF-36 (MCS). In the subsequent forward stepwise regression, two of the variables (patient and physician global VAS scores) accounted for approximately 90% of the total variance in scores. |
| C. Criterion validity | Tested |
| Comparison with a 'gold standard' Continuous scores: correlations, ROC curves Dichotomus: Sensitivity & Specificity (Describe) |
PASDAS was examined for its ability to discriminate between subjects according to the decision to change treatment at baseline. In terms of z scores by Mann-Whitney testing and ROC curves, PASDAS performed better than other measures (AUC 0.773 (0.723 to 0.822)). |