Table 5.

Univariable and multivariable logistic regression models for severe infection.

Variables	Univariable			Multivariable
	OR	95% CI	p	Coefficient	OR	95% CI	p
Age ≥50 years	1.83	0.85–3.94	0.120	−0.50	0.60	0.20–1.81	0.368
Sex (male)	1.32	0.61–2.86	0.487
Length of RA diagnosis (per 1-year increase)	1.00	0.99–1.00	0.815
Seropositivity (RF or ACPA)	1.69	0.68–4.24	0.260
Erosions on X-ray	1.22	0.58–2.59	0.599
Extra-articular manifestations	1.69	0.68–4.24	0.260
Fibromyalgia	0.52	0.18–1.56	0.247
Charlson comorbidity index (≥2)	1.39	1.12–1.73	0.003	0.99	2.69	1.03–7.00	0.043
Chronic lung disease	2.71	1.05–7.00	0.040
Diabetes mellitus	1.32	0.61–2.86	0.487
Number of regular medications (per 1 increase)	1.24	1.11–1.37	<0.001
Previous severe infection in last three years	6.02	2.48–14.62	<0.001	1.27	3.58	1.28–9.97	0.015
DAS28 (per 0.5-unit increase)	1.31	1.24–2.42	0.001	0.30	1.35	1.10–1.67	0.005
Low white blood cell counts (<4)	0.91	0.11–7.63	0.930
Low lymphocyte counts (<1)	3.64	1.27–10.48	0.016	1.41	4.08	1.16–14.29	0.028
Low neutrophil counts (<1)	1.16	0.35–5.50	0.847
Low T-cell (CD3+) counts (<688)	4.56	1.26–15.53	0.021
Low T-helper cell (CD3+/CD4+) counts (<389)	2.66	0.45–15.74	0.282
Low cytotoxic T-cell (CD3+/CD8+) counts (<309)	5.67	1.84–17.45	0.002

Variables with a p<0.10 were included in the multivariable analysis. In cases of collinearity between variables, the most statistically significant or clinically relevant factor was selected. Age was included in the multivariable model regardless of its significance because of an a priori decision about its clinical relevance.

OR: odds ratio; CI: confidence interval; RF: rheumatoid factor; ACPA: anti-citrullinated protein antibodies; DAS28: disease activity score of 28 joints.