| MEASUREMENT PROPERTIES | |
| Limitations | English only |
| Observations | |
| 1. RELIABILITY | |
| A. Internal Consistency | Tested |
| Cronbach's (Describe) |
In studies of juvenile and adult PM/DM, total MDI extent and severity of damage scores were highly correlated (Spearman’s r 0.87 in juvenile and 0.75–1.0 in adult PM/DM) |
| 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 | Tested |
| Standard error of measurement (SEM), smallest detectable change (SDC) or Limits of agreement (LoA) (Describe) |
In a study of adult patients with PM/DM, the reliability was considered good (with a ICC of 0.65 or the ratio of the estimates of the standard error attributable to the physicians to the standard error attributable to the patients 0.40) for each organ system of the MDI extent and severity scores, except for the gastrointestinal and pulmonary systems for extent of damage and the skeletal system for severity of damage. |
| 2. VALIDITY | |
| A. Content validity: face validity | Tested |
| Expert opinion (relevance and comprehensiveness) (Describe) |
The draft version of the MDI, including the glossary, was commented on and further refined by ⬎75 members of IMACS using a Delphi approach. Two interrater reliability exercises using adult and juvenile PM/DM patients were performed that resulted in further refinement of the tool based on feedback in ease of use and understanding of the experienced adult and pediatric specialists who participated |
| B. Construct Validity: Structural validity |
Not Tested |
| Hypotheses-testing | Tested |
| Cross-cultural validity | Not Tested |
| Brief Description | |
| C. Criterion validity | Tested |
| Comparison with a 'gold standard' Continuous scores: correlations, ROC curves Dichotomus: Sensitivity & Specificity (Describe) |
In patients with adult or juvenile PM/ DM, those with a chronic illness course had a higher rate of damage accumulation than those with a monocyclic or polycyclic course, and the percentage of patients with measurable damage was also greater in those with a chronic illness course |