Clinical differentiation between giant cell (temporal) arteritis and Takayasu's arteritis.

Objective: To determine whether giant cell (temporal) arteritis (GCA) can be differentiated from Takayasu's arteritis on the basis of clinical findings.
Methods: A comparative study contrasting 217 patients with GCA to 63 patients with Takayasu's arteritis was conducted, using the prospectively gathered large multicenter data set of the American College of Rheumatology Vasculitis Criteria Databank. Logistic regression and recursive partitioning were used to assess the capability of a variety of variables to separate these 2 vasculitic disorders.
Results: Age of 40 years at onset of disease was the most discriminatory single variable. Excluding age at onset, ethnic background and a combination of clinical signs indicating upper limb vascular impairment, shoulder stiffness, and tender scalp led to correct classifications of 95% in both GCA and Takayasu's arteritis. Vascular insufficiency of the upper extremities, a key feature of Takayasu's arteritis, was noted in 15% of patients with GCA, although to a lesser degree.
Conclusion: Although similar in many respects, GCA and Takayasu's arteritis were easily definable and separable disorders, even when the typical age barrier of 40 years at onset of disease was excluded. These findings strengthen the concept that they are distinct disease entities.