Table 4

Estimated sample sizes for two sided and one sided testing, based on the chronological placebo event rates, calculated for five hypothetical situations: drugs working according to the RRR model (two), the ARR model (two), and a mixed model (one)

		RRR constant				ARR constant				Mixed model
	Placebo event rate(%)	RRR = 50%		RRR = 75%		ARR = 15%		ARR = 25%		Intervention event rate = 5%
Patient group	Placebo event rate(%)	2 sided	1 sided	2 sided	1 sided	2 sided	1 sided	2 sided	1 sided	2 sided	1 sided
Early RA, disease duration <2 years; late RA: disease duration ⩾2 years; RRR, relative risk reduction = (1−(negative event rate intervention group – negative event rate placebo group)×100); ARR, attributive risk reduction = (negative event rate placebo group – negative event rate intervention group); event rate, percentage of patients with progression of joint damage larger than smallest detectable change (SDC) based on the chronological Sharp/van der Heijde change-score.
*ARR 25% not feasible owing to a placebo event rate <25%, estimated sample size based on the maximal ARR (18%).
Early RA
Regardless of baseline damage	18	227	179	84	66	60	48	37*	29*	94	74
Medium + high baseline damage, score ⩾4	35	97	76	36	28	135	106	24	19	25	20
High baseline damage, score ⩾21	64	34	27	13	10	168	132	40	32	7	5

Late RA
Regardless of baseline damage	36	92	73	34	27	138	109	25	20	23	18
Medium + high baseline damage, score⩾4	42	73	58	27	21	154	122	31	24	17	14
High baseline damage, score ⩾21	52	52	41	19	15	169	133	37	29	11	9