Validation of the giant cell arteritis probability score at a tertiary hospital

Objective: Giant cell arteritis (GCA) is a vasculitis that can cause irreversible vision loss; temporal artery biopsy (TAB) is the diagnostic gold standard, but may be overused. We hypothesized that the modified Giant Cell Arteritis Probability Score (m-GCAPS) would accurately discriminate biopsy-proven GCA and identify patients at sufficiently low pretest probability to avoid futile TAB. We aimed to externally validate m-GCAPS in a TAB cohort at a tertiary care center. Methods: This study aimed to validate the GCAPS in a cohort of patients with suspected GCA and evaluate its reliability in ruling out GCA. A retrospective cohort study of temporal artery biopsies performed at Stony Brook University Hospital from August 2002 to May 2024. Demographics, symptoms, laboratory markers, and possible alternative diagnoses were collected from hospital records. A modified version of GCAPS was used owing to poor documentation of the extracranial artery abnormality, called m-GCAPS (GCAPS without extracranial artery abnormality). Continuous variables were expressed as means with standard deviation, and categorical variables as numbers and percentages. Welch's two-sample t test, Mann-Whitney U test, and χ² test (or Fisher's exact test) were used for analysis. Discriminatory performance of m-GCAPS was determined by area under the curve of the receiver operating characteristic curve. P values of <.05 were considered statistically significant. Results: There were 167 patients who underwent TAB, and 109 patients had complete records. Of these, 20 had positive biopsies. The m-GCAPS had an area under the curve of 0.93, sensitivity of 90%, and specificity of 82% at the optimal cut-off value of >14.5. GCA prevalence was 0% in the low-risk (score <9), 0% in the intermediate-risk (9-12), and 32% in the high-risk group (>12) groups. Conclusions: Performance of the m-GCAPS for risk stratification has shown to be a promising tool for providers in an inpatient setting. This aids in identifying equivocal cases of GCA and allows surgeons to make informed decisions about who would most benefit from TAB.