Table 2

Performance of ScleroID in dcSSc by the OMERACT filter for truth and discrimination

Truth
Construct validity—does the PROM measure what it is supposed to measure?	Spearmans‘ correlation between ScleroID and: SSc-HAQ, 0.79, 95%CI (0.69, 0.86) HAQ-DI, 0.72, 95%CI (0.60, 0.80) SF-36 physical score, −0.69, 95%CI (–0.77, –0.60)
Internal consistency—do the PROM items cover all aspects they are supposed to?	Cronbach’s alpha 0.87 (good) Split-half reliability coefficient 0.88
Discrimination
Test–retest reliability—are the results reproducible in a stable population?	Intraclass correlation coefficient 0.89, 95%CI (0.84, 0.92) (excellent)
Sensitivity to change—can the PROM discriminate between groups in the setting of interest (worsened/improved)?	SRM −0.63 in the improved subgroup and 0.48 in the worsened subgroup; moderate, superior to the comparators (SSc-HAQ, EQ-5D, SF-36) Patients with no change: SRM −0.118

dcSSc, diffuse cutaneous systemic sclerosis; EQ-5D, EuroQol-5 Dimensions; HAQ-DI, Health Assessment Questionnaire Disability Index; OMERACT, Outcome Measures in Rheumatology; PROM, patient-reported outcome measure; ScleroID, Systemic sclerosis Impact of Disease; SF-36, 36-item Short Form Health Survey; SRM, standardised response mean.