Temporal Artery Biopsy in the Workup of Giant Cell Arteritis: Diagnostic Considerations in a Veterans Administration Cohort
Authors: Selby Laura D. , Park-Egan Brenna A. M. , Winges Kimberly M. 
Published: August 2020

Background:
Giant cell arteritis (GCA) is the most common systemic vasculitis in the American population older than 50 years and is a sight-threatening and life-threatening disease. It is definitively diagnosed with a temporal artery biopsy. Although there are many studies focusing on the clinical presentation and laboratory values in diagnosing GCA in the general population, studies focusing on the veteran population are lacking. This is the first study describing the diagnostic features of GCA in the US military veterans.

METHODS:
We performed a retrospective chart review in the Veterans Information Systems and Technology Architecture Computerized Patient Record System (CPRS 1.0, Department of Veterans Affairs Health Data Systems). Anatomic pathology reports from temporal artery biopsies (TABs) were collected, as well as the clinical presentation and laboratory values for each case. Frequency, sensitivity, and specificity were calculated for clinical variables, such as new-onset headache and vision changes, including diplopia, ischemic vision loss/optic disc disease, and amaurosis fugax. A logistic regression (LR) prediction model was then developed to compare veteran risk factors with those of the general population.

RESULTS:
Of 292 patients, 40 had positive TABs (13.7%). The average age of subjects with positive TABs was 73 ± 8.8 years (mean ± SD). The average erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) in patients with positive TABs (69.1 mm/hr and 56.6 mg/L, respectively) were significantly higher than ESR and CRP in patients with negative TABs (50.5 mm/hr, P = 0.0016 and 32.2 mg/L, P = 0.0394, respectively). Mean platelet levels were much higher (317.6 × 109/L) in patients with positive TABs than platelet levels in those with negative TABs (260.6 × 109/L, P = 0.0005). CRP was the most sensitive variable at 83.3%, followed by ESR with a sensitivity of 80% and new-onset headache with a sensitivity of 62.5%. Jaw claudication and polymyalgia rheumatica (PMR) were most specific (81.3% and 89.3%, respectively). Headache was the most common presenting symptom overall (71.6%), followed by vision changes (50.3%), scalp tenderness (25.7%), jaw claudication (20.9%), and PMR-related symptoms (12.7%). The LR prediction model included scalp tenderness, log (CRP), log (platelets), vision changes, and age, with 50% sensitivity and 88.36% specificity. Platelets (odds ratio [OR] = 4.309, P = 0.049), CRP (OR = 1.504, P = 0.022) and scalp tenderness (OR = 3.860, P = 0.016) were statistically significant predictors of a positive TAB in this population.

CONCLUSIONS:
Veterans Administration (VA) patients present with symptomatology similar to that of the general population. A positive biopsy was found in female veterans more frequently than in their male counterparts. Platelet count and scalp tenderness were most predictive. Our LR model provided a highly specific method for detecting GCA in the veteran population at this institution, but further studies are needed to determine the generalizability of the model. This retrospective study serves as a basis for future multicenter VA-wide studies to characterize the unique features in this population.