P304 Performance of the Southend GCA Probability Score on the NHS Lanarkshire fast track pathway

Abstract

Abstract Background/Aims Fast track GCA pathways (GCA FTP) with use of confirmatory ultrasound are growing in popularity, but the burden of referrals can overwhelm services and represents a barrier to timely assessment. The Southend GCA Probability Score (GCAPS) has shown promise in determining pre-test probability and may have a role in triage, but there is limited data supporting its use in external cohorts. We evaluated the performance of GCAPS in patients assessed on the NHS Lanarkshire GCA FTP. Methods Consecutive patients assessed on the GCA FTP between November 2018 and August 2021 were included. All underwent GCAPS assessment as part of routine care. GCAPS risk groups were defined as follows: low risk ≤8, medium risk 9-12, high risk ≥13. GCA diagnoses were supported by USS +/- TAB and confirmed at 6 months. Overall performance of GCAPS in distinguishing GCA / non-GCA final diagnoses was assessed by ROC analysis. Test characteristics for different GCAPS binary cut-offs were also determined. Results 176 patients were included in total; mean age 69.0 years (SD 9.8), 63.6% female, median GCAPS 10 (IQR 8, 14). 54 patients were diagnosed with GCA, including 0/57 low risk patients, 3/60 medium risk patients (5.0%), and 51/59 high risk patients (86.4%). ROC analysis for total GCAPS in distinguishing GCA/non-GCA gave an AUC of 0.973 (95% CI 0.951 - 0.999). A GCAPS cut-off of ≥ 13 had the highest accuracy for GCA diagnosis (93.8%), with 94.4% sensitivity and 93.4% specificity. A GCAPS cut-off of ≥ 10 captured all cases of GCA (100.0% sensitivity), with 64.8% specificity. Conclusion Performance of GCAPS as a risk stratification tool in our cohort was excellent. GCAPS may have additional roles in screening FTP referrals and guiding empirical glucocorticoid therapy. No patients with GCAPS <10 had GCA; this is consistent with previously published data and suggests specialist review and/or USS may not be required in this group. By contrast, most patients with GCAPS ≥13 had GCA, and this group is most likely to benefit from empirical glucocorticoid treatment while awaiting confirmation. Patients with GCAPS between these values should undergo prompt assessment to minimise the risk of missed diagnoses, or overtreatment. Disclosure A.R. Melville: Other; Dr Melville is a Medical Research Council and GlaxoSmithKline Experimental Medicine Initiative to Explore New Therapies clinical training fellow, with project funding outside the submitted work. K. Donaldson: Other; Speaker fees from Menarini Pharma UK. A. Ciechomska: Other; Speaker, travel and registration fee sponsorship from Novartis, Abbvie, Chugai Pharma, Colgene, Roche and Lilly.