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I don't think it can be used to prove that "A" is better than "B", but rather than "A" is effective (on it's own). In theory, if the effect of "A" and "B" are independent of each other then in a trial of "A + B" vs. "B" one would be able to extrapolate the isolated effect of "A" (assuming there are no other confounding factors). Making an assumption that "A" is better than "B" in this case cannot be made. Ahmed ________________________________ From: Evidence based health (EBH) <[log in to unmask]> on behalf of Ted Harding <[log in to unmask]> Sent: Wednesday, August 3, 2016 9:11 AM To: [log in to unmask] Subject: Re: A +B versus B design, acupunture and more In how many trials has "A+B better than B" led to a claim that "A is better than B"? Such a conclusion is clearly illogical. Counter-example: Condition being treted: Gut infection with E. Coli. Treatment A: Improve diet Treatment B: Administer antibiotics Clearly an appropriately improved diet could enhance/accelerate the effect of antibiotics on cure of the infection, so A+B is better than B alone. But merely improving the diet (A) is almost certain to be less effective than administering the antiobiotic (B). So "A+B better than B" does not imply "A better than B", and any study which made such a claim solely on the basis of that "logic" is clearly arguing illogically, and should never get past reviewers. So is that illogic a real issue in published studies (perhaps especially of acupuncture and the like)? Or is the cited article making a meaningless fuss? Or what? Best wishes to all, Ted. On 03-Aug-2016 08:28:25 Juan Gérvas wrote: > Acupuntura (y otros tratamientos). Diseño de ensayo clínico que lleva a > resultados positivos. > *Acupunture (and others treatment). A trial design that generates only > ''positive'' results.* > In recent years, we have seen a plethora of RCTs adopting a design where > patients are randomized to receive either usual care (the control group) > or usual care plus the experimental treatment. Schematically this design > could be depicted as 'A + B versus B'. At first glance, such comparisons > may seem reasonable. However, on closer inspection, doubts emerge > regarding whether such RCTs are fair scientific tests of the experimental > intervention. These doubts originate from the theoretical view that 'A > plus B' will invariably amount to more than 'B' alone. Even in cases where > treatment A is a pure placebo, its placebo and other nonspecific effects > could lead to a better outcome in the experimental group than in the > control group. This would be particularly likely if i) the experimental > treatment is associated with sizable nonspecific effects, ii) a subjective > outcome measure is used, and iii) the experimental intervention 'A' causes > a deterioration of the condition being treated. > http://www.jpgmonline.com/article.asp?issn=0022-3859;year=2008;volume=54;issue Page Not Found : Journal of Postgraduate Medicine: Free full text articles from JPGM, India, an indexed medical periodical <http://www.jpgmonline.com/article.asp?issn=0022-3859;year=2008;volume=54;issue> www.jpgmonline.com Indexed peer-reviewed biomedical periodical of Staff Society of Seth GS Medical College and KEM Hospital, India, with free access to full-text since 1990. > =3 > ;spage=214;epage=216;aulast=Ernst > > *Effectiveness of acupuncture for the prevention of episodic migraine. > Cochrane. NNTB of 4.* > http://www.ncbi.nlm.nih.gov/pubmed/27351677?dopt=Abstract > -un saludo juan gérvas @JuanGrvas ------------------------------------------------- E-Mail: (Ted Harding) <[log in to unmask]> Date: 03-Aug-2016 Time: 10:11:30 This message was sent by XFMail -------------------------------------------------