NOTE: This algorithm was suggested by Dr Eddy Lang and X. Xue of the Emergency Department, SMBD Jewish General Hospital, McGill University, Montreal, Canada. Their version of the algorithm is available in the "Contributed Algorithm" section.
Parameters:
(1) survival probability in the control group at a given time
(2) hazard ratio (HR)
(3) standard error (SE) for the hazard ratio
hazard ratio =
= EXP(hr)
hr =
= LN(HR)
lower 95% confidence interval for hazard ratio =
= EXP((hr) - (1.96 * (standard error)))
upper 95% confidence interval for hazard ratio =
= EXP((hr) + (1.96 * (standard error)))
number needed to treat =
= 1 / (((survival probability of control group)^(hazard ratio)) - (survival probability of control group))
number needed to treat at lower 95% confidence interval =
= 1 / (((survival probability of control group)^(lower 95% CI for HR)) - (survival probability of control group))
number needed to treat at upper 95% confidence interval =
= 1 / (((survival probability of control group)^(upper 95% CI for HR)) - (survival probability of control group))
