Table 4.

Multivariate analysis of independent risk factors for serious infections in the Registry of Japanese Rheumatoid Arthritis Patients for Longterm Safety (REAL) database. The relative risk (RR) of biologics for development of serious infection for up to 1 year of the observation period was calculated using the Poisson regression model after adjusting for the confounding factors of age, chronic pulmonary disease, Steinbrocker stage, disease activity, corticosteroid dosage, and methotrexate dosage.

	RR (95% CI)	p
TNF inhibitor^* (yes)	2.37 (1.11–5.05)	0.026
Age, by decade	1.82 (1.32–2.52)	0.00031
Chronic pulmonary disease (yes)	2.61 (1.38–4.94)	0.0031
Stage III or IV (vs Stage I or II)^**	2.07 (1.07–3.97)	0.030
MTX dose > 8.0 mg/wk	2.61 (1.40–4.86)	0.0024
DAS28 (3/CRP)	0.87 (0.66–1.14)	0.31
Prednisolone dose > 7.5 mg/day	1.21 (0.58–2.55)	0.61

↵* Infliximab or etanercept.
↵** Steinbrocker classification¹⁹ was used to define RA disease stages. TNF: tumor necrosis factor-α; DAS28: 28-joint count Disease Activity Score; CRP: C-reactive protein; MTX: methotrexate.