Outcome Measures in Large‐Vessel Vasculitis: Relationship Between Patient, Physician, Imaging, and Laboratory‐Based Assessments

OBJECTIVE: To assess the relationship between measures of disease assessment in patients with large-vessel vasculitis. METHODS: Patients with giant cell arteritis (GCA) or Takayasu's arteritis (TAK) were recruited into a prospective, observational cohort. Assessments within the following outcomes were independently recorded: (a) patient-reported outcomes (PROs) [multi-dimensional fatigue inventory (MFI); patient global assessment (PtGlobal); 36-item short form health survey (SF-36); brief-illness perception questionnaire (BIPQ)], (b) physician-reported outcomes [physician global assessment (PhGlobal)], (c) Laboratory outcomes [CRP, ESR], and (d) imaging outcomes [PETVAS, a qualitative score of vascular FDG-PET activity]. RESULTS: Analyses were performed on 112 patients (GCA=56, TAK=56), over 296 visits, with median follow-up of 6 months. Correlation network analysis revealed assessment measures clustered independently by type of outcome. PhGlobal was centrally linked to all other outcome types, but correlations were modest (ρ=0.12-0.32, p< 0.05). PETVAS, CRP, and PtGlobal were independently associated with clinically active disease. All four PROs strongly correlated with each other (ρ=0.35-0.60, p< 0.0001). PROs were not correlated with PETVAS and only PtGlobal correlated with CRP (ρ=0.16, p< 0.01). Patients whose clinical assessment changed from active disease to remission (n=29) had corresponding significant decrease in ESR, CRP, and PETVAS at the remission visit. Patients whose clinical assessment changed from remission to active disease (n=11) had corresponding significant increase in CRP and PtGlobal at the active visit. CONCLUSIONS: Measures of disease assessment in large-vessel vasculitis consist of independent, yet complementary outcomes, supporting the need to develop composite outcome measures or a standard set of measures covering multiple types of outcomes.