| MEASUREMENT PROPERTIES | |
| Limitations | <5 European languages (English) |
| 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) |
Clinician reliability exceeded the threshold of acceptability for dermatologists and clinical trial investigators: 0.85 and 0.73, respectively. ICC results indicate that clinicians were consistent in individual patient ratings. |
| C. Reliability interobserver or Measurement error | Tested |
| Standard error of measurement (SEM), smallest detectable change (SDC) or Limits of agreement (LoA) (Describe) |
Exact agreements among the dermatologists [44%] and trial investigators [61.5%] exceeded 40% of acceptability threshold. |
| 2. VALIDITY | |
| A. Content validity: face validity | Tested |
| Expert opinion (relevance and comprehensiveness) (Describe) |
All PGA-F items were locally independent and targeted patients along the severity continuum with complementary precision (item fit statistics: < the 1.5 acceptability threshold). |
| B. Construct Validity: Structural validity |
Tested |
| Hypotheses-testing | Tested |
| Cross-cultural validity | Not Tested |
| Brief Description |
The PGA-F was shown to be usable by rheumatologists to measure patients along the full range of the fingernail psoriasis severity spectrum, have a strong relationship with a conceptually similar reference measure, differentiate among patients based on fingernail psoriasis severity, and detect category severity change over a 24-week period. |
| C. Criterion validity | Not Tested |
| Comparison with a 'gold standard' Continuous scores: correlations, ROC curves Dichotomus: Sensitivity & Specificity (Describe) |
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