P207 External validation of the Southend giant cell arteritis pre-test probability score in a Dorset fast-track clinic

Abstract

Abstract Background/Aims Giant cell arteritis (GCA) is a common referral to rheumatology departments and timely and accurate diagnosis is important to prevent ischaemic complications. The current BSR and EULAR guidelines support the use of temporal and axillary artery ultrasound for ruling out GCA in low-probability cases or for confirming GCA in high-probability cases. The Southend GCA pre-test probability score (PTPS) is a tool that can be used to risk-stratify patients and guide the need for additional investigations. Previous publications have categorised patients as low-risk (PTPS <9), intermediate-risk (PTPS 9-12) and high-risk (PTPS >12). We aimed to provide external validation of the Southend PTPS by assessing its performance in patients attending the fast-track GCA clinic at Poole Hospital. Methods Between 5th January 2018 and 17th June 2022, 576 patients were seen in the GCA fast-track clinic at Poole Hospital and 506 (87.8%) had a calculated PTPS. Patients were diagnosed with ‘confirmed GCA’, ‘possible GCA’, ‘probable GCA’, ‘presumed GCA’, ‘not GCA’, or ‘large vessel vasculitis’ based on clinical, laboratory, ultrasound, biopsy or additional imaging. For the purpose of this analysis, we included only those patients who were diagnosed with ‘confirmed GCA’ (86 patients) or ‘not GCA’ (319 patients). A PTPS ≥9 was used to calculate the sensitivity, specificity, positive and negative predictive values for a diagnosis of GCA. Results The mean age of patients with ‘confirmed GCA’ in our cohort was 78.8 years and the percentage who were female was 72.1%. A PTPS ≥9 had a sensitivity of 97.7% and specificity of 63% for a diagnosis of GCA. The positive predictive value was 41.6% and negative predictive value was 99%. Conclusion Our results show that the Southend PTPS can be used to risk stratify patients into high- and low-risk groups and validates the PTPS outside the centre in which it was developed. Our results are comparable to those published by other external centres. The high negative predictive value of the test suggests it is particularly helpful in ruling out GCA and could conceivably have a role in screening referrals to the fast-track clinic; however, further work would be needed to determine the optimal cut-off score. Disclosure J. Carroll: None. F. Griffith: None. C. Fox: None. M. Khurshid: None.