We read with interest the letter of Piaggio et al. [1] challenging the methodology used in our meta-analysis using a noninferiority approach to assess both the efficacy and safety aspects of the two-dose regimen of mifepristone for medical abortion [2]. We agree that since the introduction of mifepristone at a dosage of 600 mg (600 mg being the originally approved dosage, not 200 mg), no direct comparative studies, powered to demonstrate' the difference between dosages with regard to the end point of continuing pregnancy, have been performed. This is unfortunate because, for the women concerned and with respect to the safety of the procedure, this end point is critical. It is therefore of concern that treatment regimens may be changed without evidence that these changes will not result in more adverse outcomes. The meta-analysis was performed to use what information there is in order to assess the effect of a dose of mifepristone on the critical end point of continuing pregnancy.
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