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
|