Table 5.

Multivariable logistic and linear regression comparing proportions of SARS-CoV-2 seropositivity and IgG antibody titres between patients with rheumatic immune-mediated inflammatory diseases and controls

	Seropositivity			IgG antibody titre
	OR	95% CI	P value	Beta	Ratio	95% CI	P value
Healthy controls*	1.00	N.A.		0.00	1.00	N.A.
Patients with rheumatic diseases	0.88	(0.42 to 1.83)	0.73	0.49	1.59	(0.88 to 3.02)	0.12
Covariables
Age	0.97	(0.95 to 1.0)	0.040	−0.0083	0.99	(0.97 to 1.01)	0.43
Sex
Male*	1.00	N.A.		0.00	1.00	N.A.
Female	0.83	(0.41 to 1.66)	0.59	0.30	1.35	(0.75 to 2.43)	0.32
COVID-19-related hospitalisation	0.83	(0.41 to 1.66)	0.67	−1.88	6.58	(1.76 to 24.56)	0.005†
Time since COVID-19 in months	0.95	(0.88 to 1.01)	0.10	−0.15	0.86	(0.81 to 0.91)	<0.0001†

Seropositivity data are adjusted ORs with 95% CIs in parentheses, and p values. IgG antibody titre data are adjusted β, back-transformed β (ratio) with corresponding 95% CI in parentheses, and p values. Data on IgG antibody titre were missing for 14 (4%) of 367 samples due to shortage of serum volume.

*Reference group.

†Below the Benjamini threshold.

N.A., not available.