Table 1. Clinical characteristics of EIRA and Leiden EAC studies.

Characteristics	EIRA	Leiden EAC
No. of patients	2012	1069
No. of controls	1033	867
Country of origin	Sweden	The Netherlands
Female sex, patients (%)	70.4	64
Female sex, controls (%)	74.6	21.9
Age of onset, years (mean±SD)	51.7±12.7	56.4±15.4
Disease duration, years	<1	<2
ACPA positive (%)	(1265/2012) 62.8	(375/625a) 60
HLA-DRB1 SE (patients) (%)	(1486/2012) 73.8	(590/842b) 70.1

Abbreviations: ACPA, anti-citrullinated peptide antibody; SE, shared epitope.

Details on the EIRA study¹⁹ and the Leiden EAC study²⁰ have been reported elsewhere.

^aThe number of patients with defined ACPA status.

^bThe number of patients with defined HLA-DRB1 SE status.