1. Summary of current medical evidence reporting on aspirin use in GCA.

Article	Number of participants with GCA	Methods	GCA Biopsy‐proven (%)	Number on ASA at time of diagnosis	Number started on ASA after diagnosis	Comment on adjunctive therapy	Conclusion
Berger 2009	85	Retrospective case series	78%	22	‐	22 participants took ASA treatment prior to GCA diagnosis	No benefit of established use of ASA on rate of ischaemic complications
Chuang 1982	15	Retrospective case series of PMR and GCA	‐	‐	‐	‐	‐
Lee 2006	143	Retrospective case series	73%	ASA not reported separately	ASA not reported separately	60.1% received long‐term antiplatelet or anticoagulation	16.2% versus 48% had ischaemic complication (P value < 0.0005) in favour of antiplatelet/coagulation
Liozon 2001	174	Prospective observational case series investigating permanent visual loss	84.5%	‐	‐	Low molecular weight heparin and intravenous heparin were used for visual loss	Thrombocytosis was strongly associated with risk of permanent visual loss
Narvaez 2008	121	Retrospective	73%	30	‐	30.5% were on ASA and 7% on another antiplatelet agent prior to symptoms/signs of GCA	No observed benefit of antiplatelet therapy on the incidence of ischaemic complications or disease outcome
Nesher 2004a	175	Retrospective	87%	36	41	21% were already using low‐dose ASA at time of GCA diagnosis All given prednisolone at time of GCA diagnosis	At diagnosis 8% with ASA had ischaemic complications compared to 29% who did not have ASA (P value = 0.01) At 3 months 3% with ASA had ischaemic complications compared to 13% who did not have ASA (P value = 0.02)
Souza 2013	45	Retrospective	Not known	ASA not reported separately	ASA not reported separately	32 (71.1%) were reported on aspirin	Aspirin was of statistical benefit in preventing relapse (P value = 0.023)

ASA: aspirin
 GCA: giant cell arteritis
 PMR: polymyalgia rheumatica