Dubious Mathematical Assumptions
The approach taken by Wald and Law assumes that the effects of the
various treatments proposed are additive, yet there is little evidence
presented that this is, in fact, the case. Without this assumption it is
not valid to multiply the relative risks of the various treatment
strategies in order to determine the overall effect of the combined
treatments. There may be interactions between the treatments, whereby one
treatment may negate the effect of one or more of the other treatments.
This could only be determined if comparative trials, with combined
treatment arms, had been performed. Hence, the authors have proposed an
interesting hypothesis that deserves to be tested, but they have not
provided convincing evidence that their proposed combination of treatments
should be adopted into clinical practice.
Competing interests: No competing interests