Table 3.

Impact of the treatment effect changes on bias

Number of studies=5	Number of patients=100				Group ratio=1		Control arm probability=0.001				Number of simulated data sets=2500				Between-study SD=0.5
	Excluding BA0E studies										Including BA0E studies
	Positive treatment effect						No treatment effect				Positive treatment effect
	OR=1.25		OR=2		OR=5		OR=1		OR=1		OR=1.25		OR=2		OR=5
Methods		%bias		%bias		%bias		%bias		% bias		%bias		%bias		%bias
IV random effects	1.11	−12.6	1.45	−37.9	2.28	−119.3	1.01	0.8	1.00	<0.1	1.03	−21.4	1.13	−77.0	1.56	−220.5
IV fixed effects	1.11	−12.6	1.46	−37.0	2.28	−119.3	1.01	0.7	1.00	<0.1	1.03	−21.4	1.15	−73.9	1.56	−220.5
M-H random effects	1.11	−12.5	1.45	−37.9	2.28	−119.3	1.01	0.8	1.00	<0.1	1.03	−21.4	1.13	−77.0	1.56	−220.5
M-H fixed effects	1.11	−12.6	1.46	−37.0	2.30	−117.4	1.01	0.8	1.00	<0.1	1.03	−21.4	1.15	−73.9	1.62	−208.6
Peto	1.19	−5.0	1.87	−7.0	3.68	−35.9	1.01	1.4	1.00	<0.1	1.04	−20.2	1.19	−68.1	1.92	−160.4
	Negative treatment effect						No treatment effect				Negative treatment effect
	Excluding BA0E studies										Including BA0E studies
	OR=0.8		OR=0.5		OR=0.2						OR=0.8		OR=0.5		OR=0.2
		%bias		%bias		%bias						%bias		%bias		%bias
IV random effects	0.88	−9.9	0.70	−40.6	0.47	−133.1					0.99	−23.2	0.97	−93.0	0.94	−370.7
IV fixed effects	0.88	−9.9	0.70	−40.6	0.47	−133.1					0.98	−23.0	0.96	−92.3	0.93	−367.4
M-H random effects	0.88	−9.9	0.70	−40.6	0.47	−133.1					0.99	−23.2	0.97	−93.0	0.94	−370.7
M-H fixed effects	0.88	−9.9	0.70	−40.6	0.47	−133.1					0.98	−23.0	0.96	−92.3	0.93	−367.4
Peto	0.80	0.2	0.54	−7.8	0.26	−30.6					0.95	−22.6	0.90	−90.6	0.92	−360.9

, when OR <1. , when OR≥1. Negative (−) bias indicates underestimating of treatment effect; positive bias indicates overestimating of treatment effect.

BA0E, both-armed zero-event; IV, inverse variance; M-H, Mantel-Haenszel.