To assess the relationship between measures of disease assessment in patients with large vessel vasculitis.
Patients with giant cell arteritis (GCA) or Takayasu arteritis (TAK) were recruited into a prospective, observational cohort. Assessments within the following outcomes were independently recorded: 1) patient-reported outcomes (Multidimensional Fatigue Inventory, patient global assessment of disease activity [PtGA], Short Form 36 health survey [SF-36], Brief Illness Perception Questionnaire), 2) physician global assessment of disease activity (PhGA), 3) laboratory outcomes (C-reactive protein [CRP] level, erythrocyte sedimentation rate [ESR]), and 4) imaging outcomes (PETVAS, a qualitative score of vascular 
Analyses were performed on 112 patients (GCA = 56, TAK = 56), over 296 visits, with a median follow-up of 6 months. Correlation network analysis revealed assessment measures clustered independently by type of outcome. PhGA was centrally linked to all other outcome types, but correlations were modest (ρ = 0.12-0.32; P < 0.05). PETVAS, CRP level, and PtGA were independently associated with clinically active disease. All 4 patient-reported outcomes strongly correlated with each other (ρ = 0.35-0.60; P < 0.0001). Patient-reported outcomes were not correlated with PETVAS, and only PtGA correlated with CRP level (ρ = 0.16; P < 0.01). Patients whose clinical assessment changed from active disease to remission (n = 29) had a corresponding significant decrease in ESR, CRP level, and PETVAS at the remission visit. Patients whose clinical assessment changed from remission to active disease (n = 11) had a corresponding significant increase in CRP level and PtGA at the active visit.
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.