AB0702 Alkaline phosphatase as a predictor of giant cell arteritis – a retrospective analysis of clinical features and temporal artery biopsy findings
Authors: S. Varrier, C. Li
Journal: Annals of the Rheumatic Diseases (2018)

<h3>Background</h3> Giant cell arteritis (GCA) is the most common large vessel vasculitis in the United Kingdom and Northern Europe. Inadequate treatment and delay in diagnosis can lead to a number of devastating consequences. <h3>Objectives</h3> This study looks at whether the presence of a raised alkaline phosphatase (ALP) may aid the diagnosis of GCA, improve the sensitivity of TAB, including in the presence of other proven serum markers and whether it has any correlation with severity of clinical presentation. <h3>Methods</h3> Retrospective multicenter cohort study. Information was retrospectively gathered on patients who underwent TABs following a clinical working diagnosis of GCA. Only patients who fulfilled the American College of Rheumatology (ACR) classification criteria and had ALP measured within 4 weeks of undergoing TAB were included in the study. Once patients were identified, further information was extrapolated including the values of other serum markers taken, and presenting clinical features. <h3>Results</h3> Our 223 patients sample population who fulfilled the inclusion criteria reflected typical GCA patients: 147 (65.9%) were female and mean age was 73.1 years (SD 10.5). TAB was positive in 54 patients (24.2%). Two patients (3.7%) who had a positive TAB had completely normal serum markers. We were unable to comment on variables, which could have contributed to this but hey likely represented already administered aggressive glucocorticoid treatment at time of serum measurement or atypical presentation of GCA. Raised ALP sensitivity at the current cut off value was very low (14.8%) but with high specificity (90.5%), which was reinforced following ROC curve analysis. Pearson coefficient analysis suggested that there was a weakly associative relationship between raised ALP and degree of clinical suspicion (Correlation 0.346, Sig 0.01) <h3>Conclusions</h3> Patients with a higher level of clinical suspicion and TAB positivity were more likely to have a raised ALP. However, the association strength was weak. ALP is suggested to be highly specific for TAB positivity. The association of raised ALP to degree of clinical features and suspicion of GCA is weak and of low significance, likely a reflection of the limitations of this study. Further robust research may further evaluate this observed relationship. <h3>References</h3> [1] Yates M, Graham K, Watts RA, MacGregor AJ. The prevalence of giant cell arteritis and polymyalgia rheumatica in a UK primary care population. BMC Musculoskelet Disord. 172016. [2] Ness T, Bley TA, Schmidt WA, Lamprecht P. The Diagnosis and Treatment of Giant Cell Arteritis. Dtsch Arztebl Int. 2013;110(21):376–86. [3] Nordborg C, Nordborg E, Petursdottir V. Giant cell arteritis. Epidemiology, etiology and pathogenesis. Apmis. 2000;108(11):713–24 [4] Hunder GG, Bloch DA, Michel BA, Stevens MB, Arend WP, Calabrese LH, et al. The American College of Rheumatology 1990 criteria for the classification of giant cell arteritis. Arthritis Rheum. 1990;33(8):1122–8. [5] [5] Walvick MD, Walvick MP. Giant cell arteritis: laboratory predictors of a positive temporal artery biopsy. Ophthalmology. 2011;118(6):1201–4. [7] Sheehan NJ. Alkaline phosphatase and gamma-glutamyltransferase in polymyalgia rheumatica and giant cell arteritis. Ann Rheum Dis. 1985;44(9):644–5. <h3>Acknowledgements</h3> I would like to acknowledge the involvement of Dr. Sam Norton, MSc supervisor and statistician, Kings College London, Dr. Joe Li and Dr. Alexis Jones with Data collection. <h3>Disclosure of Interest</h3> None declared