Background Classification criteria are often used to standardize the enrollment of patients (pts) in clinical studies. American College of Rheumatology (ACR) classification criteria for giant cell arteritis (GCA)¹ are >25 years old. Advances in diagnosis and clinical understanding of GCA make their relevance to current studies questionable.

Objectives To compare inclusion criteria for the GiACTA (tocilizumab for GCA) study² with 1990 ACR GCA classification criteria.

Methods Pts were enrolled into GiACTA according to study inclusion criteria and were evaluated as to whether they met the 1990 ACR classification criteria (Table). Data are from a live database.

Results Of the 251 pts enrolled into GiACTA, 198 (79%) pts met the 1990 ACR classification criteria. The 53 pts who did not fulfill ACR criteria were eligible for GiACTA based on cross-sectional imaging studies and/or polymyalgia rheumatica (PMR) symptoms. In total, 156 (62%) pts had positive temporal artery biopsies (TAB); of these, 24 also had positive imaging findings. The remaining 95 (38%) pts had no TAB or negative TAB; diagnosis of GCA was confirmed by positive findings from large-vessel imaging studies. Positron emission tomography (PET), often coupled with computed tomography (CT), was important in diagnosis. Positive PET/CT findings contributed to GCA diagnosis in 97 (39%) GiACTA pts. CT angiography and magnetic resonance angiography contributed to diagnosis in 14 (6%) and 8 (3%) pts, respectively. New-onset headache, the only GCA symptom in the ACR criteria, was absent in 33% of GiACTA pts. However, other symptoms that often accompany GCA (PMR, scalp tenderness, jaw claudication, ischemia-related vision loss) were present in 62%, 36%, 34%, and 10% of pts, respectively.

Conclusions The 1990 ACR classification criteria for GCA require updating. Cross-sectional imaging, particularly PET/CT, now plays a major role in establishing the diagnosis of GCA. Symptoms in addition to headache merit consideration as part of revised classification criteria.

1. Arthritis Rheum 1990;33:1122.

2. Int J Rheumatol 2013;2013:912562. doi: 10.1155/2013/912562.

Disclosure of Interest K. Tuckwell Shareholder of: Roche, Employee of: Roche Products Ltd., N. Collinson Shareholder of: Roche, Employee of: Roche Products Ltd., M. Klearman Shareholder of: Roche, Employee of: Genentech, S. Dimonaco Employee of: Roche Products Ltd., J. Stone Grant/research support from: Roche, Genentech, Consultant for: Roche, Genentech