Spondyloarthritis & psoriatic arthritis
Assessing internal construct validity of DAPSA and DAPSA28 in psoriatic arthritis: a European observational study using confirmatory factor analysis and additional psychometric testing
Authors' conclusion
Overall, the model fit was acceptable across model fit statistics, supporting internal construct validity, but some evidence of misfit at country level was disclosed. Our findings support acceptable internal consistency reliability, but DIF was found for sex and country.
Study context
- Population
- Patients with PsA in the European Spondyloarthritis (EuroSpA) Research Collaboration Network with DAPSA and DAPSA28 scores at baseline and follow-upsubset of 625 for most analyses
- Participants
- 1,865 patients
- Comparison
- DAPSA vs DAPSA28
- Outcome
- Internal construct validity (scree plots, CFA, SEM), DIF and internal consistency reliability (Cronbach's α)
Methodological detailsmulticentre (EuroSpA Research Collaboration Network), confirmatory factor analysis, structural equation modelling
- Multicentre (EuroSpA Research Collaboration Network)
- Confirmatory factor analysis
- Structural equation modelling
Performance
As reported in the abstract
DAPSA
0.020
RMSEA
DAPSA28
0.034
RMSEA
Further findings
| Outcome | DAPSA | DAPSA28 |
|---|---|---|
| Internal consistency reliability (Cronbach's α) | 0.65 | 0.63 |
One-dimensional confirmatory factor analysis (CFA) model fit at follow-up (RMSEA) · 6 months
- Model fit at 6 months follow-up was poor (RMSEA, DAPSA and DAPSA28 respectively)
- 0.057, 0.063
Structural equation modelling (SEM) combining baseline and follow-up data
- Could not identify an acceptable model fit
Differential item functioning (DIF)
- DIF found for sex and country
Internal consistency reliability (Cronbach's α)
- Acceptable internal consistency
Heterogeneity across countries
- Heterogeneity across countries was observed
Original publication
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