Fig. 1

The discriminating ability for GCA and TAK of a combination of clinical parameters was evaluated by C-statistic. Gray highlighting indicates that the item is included in the model 1–7 (A). ESR of ≥ 50 mm/hr or CRP of ≥ 1.0 mg/dL was included in all models. Age at onset ≥ 50 years¹, positive temporal artery biopsy², cranial signs and symptoms (new headache, scalp tenderness, abnormal examination of the temporal artery, sudden visual abnormalities, and jaw claudication)³, PMR, descending thoracic-abdominal aorta involvement⁴, bilateral axillary artery involvement⁵, bilateral subclavian and/or axillary artery involvement⁶ were selected as clinical parameters. The ROC curve was drawn to calculate the area under the ROC curve as a C-statistic. The C statistic represents the ability to discriminate GCA from TAK in model 1 (B), model 2 (C), model 3 (D), model 4 (E), model 5 (F), model 6 (G), and model 7 (H). A value for the C-statistic greater than 0.7 indicates a reasonable and good ability to discriminate between patients with GCA and TAK. CI, confidence interval; ROC, receiver operating characteristic; TAK, Takayasu arteritis