Patient-reported outcome for physical function in idiopathic inflammatory myopathy

There is an unmet need to develop patient-reported outcomes measures for idiopathic inflammatory myopathies (IIM). We aimed to investigate the feasibility, compliance and psychometric properties of the National Institutes of Health's Patient-Reported Outcomes Measurement Information System (PROMIS) physical function-20 (PF-20) in a large US IIM population.

'Myositis Patient Centered Tele-Research' (My PACER) is a multicentre prospective observational study of IIM patients, competitively recruited through traditional in-person clinic visits [centre-based cohort (CBC)], and remotely using smartphone- and web-based technology [tele-research cohort (TRC)]. The CBC was further randomly divided (1:1 ratio) into a traditional local subcohort and a remote subcohort. Data collected included patient-reported outcomes and other patient self-assessments monthly for 6 months. Clinician-reported outcomes were obtained at baseline and 6 months.

A total of 120 IIM patients were enrolled (82 TRC/38 CBC, mean ± s.d. age 55 ± 13.4 years, 75% females, 81% Caucasians), with similar demographics and mean PROMIS PF-20 score between cohorts. The PROMIS PF-20 score was not associated with age, sex or race. The compliance and completion rates were similar between TRC and CBC as well as subcohorts. PROMIS PF-20 showed strong test-retest reliability at 1 month. PROMIS PF-20 was significantly associated with all core set measures except extra-muscular global and creatine kinase, as well as with most symptoms, and function and physical activity measures. PROMIS PF-20 illustrated concordant change with myositis response criteria and patient assessment, with a large effect size.

PROMIS PF-20 demonstrates favourable psychometric properties including reliability, validity and responsiveness in a large cohort of myositis patients, with similar adherence in local or remotely enrolled patients.