Negative temporal artery biopsy: predictive factors for giant cell arteritis diagnosis and alternate diagnoses of patients without arteritis

To investigate whether among patients with a negative temporal artery biopsy (TAB) there are clinical features that may differentiate between patients with an eventual diagnosis of giant cell arteritis (GCA) and those without arteritis, and to assess the eventual diagnoses of patients without arteritis. Retrospective analysis of patients with a negative TAB performed between 1/1/2000 and 31/12/2015. Information collected included baseline clinical and laboratory data. Patients' final diagnoses were obtained from medical records. Patients eventually diagnosed with GCA were compared with those without arteritis, and predictive features for GCA diagnosis were assessed. A total of 154 patients with a negative TAB were included in the study. Among them, 31 (20%) were eventually diagnosed with GCA. The leading alternative diagnoses of patients without arteritis were self-limited disease (23%), isolated polymyalgia rheumatica (PMR) (18%), and neurological conditions (17%). In the multivariate analysis, predictors for diagnosis of GCA among patients with a negative TAB included PMR (OR = 2.86, 95% CI 1.06-7.69), platelet count (OR = 1.28, 95% CI 1.07-1.53), and ACR score > 2 (OR = 13.4, 95% CI 4.27-42.03). Among patients with a negative TAB, the best predictors for diagnosis of GCA are fulfillment of the ACR criteria, a clinical diagnosis of PMR, and high platelet levels. These features may aid in the diagnostic work-up of patients with a negative TAB.