Table 3

Expected and observed numbers and rates of serious infections for V.1 (per 100 patient-years) and V.2 (% of patients with at least one serious infection during 12 months)

	n	PY	V.1: Number of serious infections per 100 PY (CI)				V.2: Number and percentage of patients affected by at least one serious infection per year (CI)
	n	PY	Exp. n	Obs. n	Exp. rate/100 PY	Obs. rate/100 PY	Exp. n	Obs. n	Exp. per year (%)	Obs. per year (%)
TNFα inhibitor, no risk factor	764	1059	16.8	16	1.6	1.5 (0.9–2.5)	15.3	16	1.4	1.5 (0.9–2.5)
nbDMARD, no risk factor	632	816	7.0	6	0.9	0.7 (0.3–1.6)	6.4	6	0.8	0.7 (0.3–1.6)
TNFα inhibitor, ≥1 risk factor*, no GC	635	871	28.9	37	3.3	4.3 (3.0–5.9)	25.4	33	2.9	3.8 (2.6–5.3)
nbDMARD, ≥1 risk factor*, no GC	674	939	15.5	19	1.7	2.0 (1.2–3.2)	14.0	19	1.5	2.0 (1.2–3.2)
TNFα inhibitor + GC, no other risk factor	225	196	8.6	5	4.4	2.6 (0.8–6.0)	7.4	4	3.8	2.0 (0.6–5.2)
nbDMARD + GC, no other risk factor	128	86	1.9	2	2.2	2.3 (0.3–8.4)	1.7	2	2.0	2.3 (0.3–8.4)
TNFα inhibitor, ≥1 risk factor* + GC	206	160	15.3	11	9.6	6.9 (3.4–12.3)	12.8	11	8.0	6.9 (3.4–12.3)
nbDMARD, ≥1 risk factor* + GC	141	96	5.1	8	5.3	8.3 (3.6–16.4)	4.4	8	4.6	8.3 (3.6–16.4)
TNFα inhibitor total	1830	2286	69.6	69	3.0	3.0 (2.3–3.8)	60.9	64	2.7	2.8 (2.2–3.7)
nbDMARD total	1575	1937	29.6	35	1.5	1.8 (1.2–2.5)	26.6	35	1.4	1.8 (1.2–2.5)

Bold: The confidence intervals of the observed rates overlap with the expected rates. There is no other test for insignificant difference necessary or sensible.
*At least one of: chronic lung disease, chronic renal disease, age above 60 years, previous serious infection, high number of DMARD failures. GC: treatment with glucocorticoids ≥7.5 mg/day prednisolone equivalent.
exp, expected; obs, observed; nbDMARD, non-biological disease-modifying antirheumatic drug; PY, patient-years; TNF, tumour necrosis factor.