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We read with interest, the comments of Drs Landewé and van der Heijde1 concerning our article on the treatment of patients with rheumatoid arthritis with an extract of Tripterygium wilfordii Hook F (TwHF).2 We are aware that non-inferiority trial design can be complex, and agree there are limitations of the study (TRIFRA; Comparison of Tripterygium wilfordii Hook F with methotrexate in the treatment of active rheumatoid arthritis). We hope that we can further clarify the trial design and its implications.
First, and most important, the TRIFRA study was designed as a non-inferiority trial from the very beginning. If this point was confusing in the final manuscript, we apologise, but the intent was always to design and carry out a non-inferiority trial comparing the extract of TwHF to methotrexate. As detailed in the Statistical Analysis Plan (developed in February 2012 and published as additional material), the a priori hypothesis underlying this trial was that the extract of TwHF was non-inferior to methotrexate (MTX) in treating subjects …