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Hi all, To calculate the Numbers Needed to Treat (NNT) statistic for response rates when the effect size is shown as an odds ratio I carry out the following calculation: NNT = (1-(CER*(1-OR))) / ((1-CER)*(CER)*(1-OR))* CER = Control Event Rate OR = Odds Ratio My query occurs when I am calculating this for an indirect comparison. So for example if I am comparing A and B vs a common comparator C I have the following set up: Trial 1 - A vs C: Response rate A = 0.8 Response rate C = 0.6 Trial 2 - B vs C: Response rate B = 0.7 Response rate C = 0.55 Indirect comparison gives (for example) A vs B odds ratio of 0.85 (0.6, 1.2) Is it valid to calculate the NNT by substituting CER = 0.8 and OR = 0.85 into the first equation*? All comment gratefully recieved, Thanks, Richard