Table 4.

Number of prevented events and number needed to treat^a, translated in populations A, B and C, using various trial efficacy metrics estimated using summary data from trials 1 and 2, for drugs 1 and 2

Efficacy metric	Drug 1						Drug 2
	Trial 1 in population			Trial 2 in population			Trial 1 in population			Trial 2 in population
	A	B	C	A	B	C	A	B	C	A	B	C
NPEpop
OR	313	282	105	335	302	507	429	313	535	548	400	684
RR	285	257	148	325	293	492	285	208	356	448	327	560
AB	100	90	151	63	57	96	100	73	125	87	64	109
NNTpop
RR	100	111	107	88	97	94	100	137	130	64	87	83

Example of interpretation: the true NPE for population 2 and drug 2, directly computed on the R_c distribution in population 2 with the Wang model (see Sect. 2) is 1265. The NPE in this population with drug 2 computed with the AB from trial 2 summary data is 1382. The ratio 1382/1265 in percent is 109%. It gives the value of the bias in estimating population C NPE with the AB computed on trial data. As it is often done in translation process, RR computed from trial summary data is used for translating the efficacy of new drug. In the considered case, this gives a translated NPE = 7084, thus a bias ratio = 560%

AB absolute benefit, N population size, NNT number needed to treat, NNT_pop number needed to treat in the population, NPE_pop number of prevented events in the population, OR odds ratio, RR relative risk

^aThe NPE and NNT are expressed as a percentage of the true values