Ab1317 the Performance of Giant Cell Arteritis Probability Score in Real Life Among the Population of Northwest England

Background: Giant cell arteritis (GCA) is the most common large vessel vasculitis with potentially harmful treatment with high-dose steroids with life-changing complications like blindness, abdominal and aortic aneurysms and stroke. The Giant Cell Arteritis Probability Scoring (GCAPS) system was proposed by Laskou F et al. in 2019 to aid in diagnosing GCA through a retrospective study of 122 patients. It was recently externally validated by Melville A R et al. in 2021 at Lanarkshire among 129 patients with suspected GCA and 135 patients by Neuman L M et al. in 2022 in the Netherlands. They established a cut-off of 13 on GCAPS as a threshold to diagnose disease. Objectives: We aimed to assess the performance of GCAPS in real life at Morecambe University Hospital NHS Trust. Methods: Data were collected prospectively between September 2019 and November 2023 for consecutive patients referred by primary and secondary care to our Rheumatology department. Patient demographics, referral time to assessment, presenting symptoms, initial inflammatory markers, biopsy result and diagnosis at six-month follow-ups were collected. Retrospectively, patients referred were categorised into confirmed GCA, probable and possible GCA and not GCA. The GCAPS score of each category was then examined retrospectively to determine if the cut-offs seen in the other studies would perform as well in real life. Statistical analysis was done with STATA software using a Poisson regression model to establish a relationship between the GCAPS, symptoms and inflammatory markers, and a co-relation model was used to establish a relation between GCAPS and GCA. Results: The cohort comprised ninety females (73%) and thirty-three males aged 51 to 93 years. In total, 70 patients were categorised as GCA based on initial clinical suspicion. GCA was confirmed in twenty-four patients with mean GCAPS of 12.85 (SD3.50), with ages ranging from 62 to 87. Further, twenty-five patients (age range 67 to 92 years old) treated as probable GCA had mean GCAPS of 10.64 (SD 2.70), and twenty-one possible GCA patients aged 54 to 87 had mean GCAPS of 9.80 (SD 2.63). Negative/untreated GCA patients' GCAPS was 6.72, (SD 2.08) and were between 51 and 93 years old (see Figure 1). We have found a statistically significant correlation in between GCAPS score with higher age (p=0.00), Jaw claudication (p=0.00), raised CRP (p=0.000), ESR (p=0.000) and visual changes (p=0.007). Other symptoms like headache, polymyalgia, arthritis, aura, lethargy, mood, and visual symptoms were not statistically significant. Conclusion: GCAPS cut-off of 13 (SD 3.50) strongly predicts GCA diagnosis, whereas GCAPS of 7 (SD 2.08) effectively excludes GCA. This agrees with previous studies and provides further validation of this method of assessment. Hence, it is a useful real-life scoring system and can be implemented as a screening guide for referral to specialist centres. REFERENCES: 1 Rheumatology Advances in Practice 6.1 (2022): rkAB102. 2 CLIN EXP RHEUMATOL 40 (2022): 787-92. Acknowledgements: NIL. Disclosure of Interests: None declared.