VALIDATION DATA

MEASUREMENT PROPERTIES
Limitations
Observations
1. RELIABILITY
A. Internal Consistency Not Tested
Cronbach's (Describe)
B. Reliability intraobserver or test-retest Tested
Continuous scores: intraclass
correlation coefficient (ICC)
Dichotomus: Cohen kappa (Describe)

Reliability of the instrument as a whole has not yet been assessed, although components are commonly used in RCTs and have performed reliably in similar measures.
C. Reliability interobserver or Measurement error Not Tested
Standard error of measurement (SEM),
smallest detectable change (SDC) or
Limits of agreement (LoA) (Describe)
2. VALIDITY
A. Content validity: face validity Not Tested
Expert opinion (relevance and
comprehensiveness) (Describe)
B. Construct Validity:
Structural validity		 Tested
Hypotheses-testing Tested
Cross-cultural validity Tested
Brief Description

In a principal component analysis (PCA), three components with a total of five items were revealed to best reflect disease activity of PsA. These components were (1) patient-reported outcomes, displayed most strongly by PtGA and pain assessments; (2) joint involvement, signified best by the 66 SJC and 68 TJC; and (3) acute phase response, represented best by C reactive protein (CRP).
C. Criterion validity Tested
Comparison with a 'gold standard' Continuous scores:
correlations, ROC curves Dichotomus:
Sensitivity & Specificity (Describe)

DAPSA correlated highly with other measures, including the Disease Activity Score in 28 joints (DAS28), Simplified Disease Activity Index, and Clinical Disease Activity Index.
A post hoc analysis compared the achievement of DAPSA REM/LDA with very low disease activity (VLDA)/minimal disease activity (MDA) targets in tofacitinib-treated patients with PsA. Pooled data from two phase 3 studies of patients with PsA receiving tofacitinib showed that achieving DAPSA-REM/DAPSA-LDA or VLDA/MDA was associated with improved Health Assessment Questionnaire-Disability Index (HAQ-DI) and Short Form-36 Health Survey Physical Component Summary (SF-36 PCS) scores. Increased disease activity at baseline was associated with reduced likelihood of achieving DAPSA-REM/DAPSA-LDA or VLDA/MDA at month 3. The analysis revealed moderate agreement (kappa values 0.41-0.60) between DAPSA-REM and VLDA, and DAPSA-LDA and MDA from months 1 to 6. However, over half of patients achieving DAPSA-REM and over two thirds of patients achieving DAPSA-LDA were not captured by VLDA and MDA. VLDA and MDA may be more difficult to achieve than DAPSA-REM and DAPSA-LDA, respectively. Slightly reduced radiographic progression at month 12 was also associated with achieving DAPSA-REM/DAPSA-LDA or VLDA/MDA. These data suggest that DAPSA and VLDA/MDA are useful tools for evaluating disease activity and treatment response in PsA. The clinical and prognostic relevance of these findings should be determined.