the online version of this article ( doi:10.1007/s13300 - 014 - 0066-y ) contains supplementary material , which is available to authorized users . supplementary material 1 ( pdf 190  kb ) supplementary material 1 ( pdf 190  kb ) andrea messori , valeria fadda , dario maratea , sabrina trippoli and claudio marinai declare no conflict of interest . the analysis in this article is based on previously conducted studies , and does not involve any new studies of human or animal subjects performed by any of the authors . this article is distributed under the terms of the creative commons attribution noncommercial license which permits any noncommercial use , distribution , and reproduction in any medium , provided the original author(s ) and the source are credited .
backgroundin studying the therapeutic evidence of innovative drug treatments , increasing attention is being devoted to differentiating between results that indicate no significant differences among the treatments under examination (  no proof of difference  ) and results that demonstrate the therapeutic equivalence among the treatments (  proof of no difference).aimour analysis was aimed at evaluating the degree of therapeutic equivalence for dipeptidylpeptidase-4 ( dpp-4 ) inhibitors given in type 2 diabetes as monotherapy or in combination with metformin.methodsequivalence was determined by developing a standard forest plot that incorporated the information on margins previously reported in randomized trials on these agents . 
 the end point was hba1c change from baseline ; the equivalence margin was set at 0.25% change in hba1c . 
 the clinical material was obtained from a systematic review on this topic.resultsgiven as monotherapy , linagliptin , sitagliptin , and vildagliptin ( but not saxagliptin ) met the equivalence criterion when compared with one another . 
 given in combination with metformin , linagliptin , saxagliptin , sitagliptin , and vildagliptin showed an equivalent effect whereas alogliptin did not satisfy the equivalence criterion.conclusionsconsidering the most recent therapeutic guidelines , our results are of interest particularly as regards the information on dpp-4 inhibitors in combination with metformin . 
 four of the five dpp-4 inhibitors under examination clearly showed to have the same effectiveness ; the fifth agent  alogliptin  failed to meet the equivalence criterion , but only because its superiority could not be excluded.electronic supplementary materialthe online version of this article ( doi:10.1007/s13300 - 014 - 0066-y ) contains supplementary material , which is available to authorized users .