Hum. Reprod. Advance Access originally published online on September 30, 2004
Human Reproduction 2004 19(11):2537-2544; doi:10.1093/humrep/deh475
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The place of the crossover design in infertility trials: a maximum likelihood approach
1 Institute for Medical Technology Assessment, Erasmus University, Rotterdam and 2 Division of Reproductive Endocrinology and Fertility, Institute for Endocrinology, Reproduction and Metabolism, Vrije Universiteit Medical Centre, Amsterdam, The Netherlands
3 To whom correspondence should be addressed at: Division of Reproductive Endocrinology and Fertility, Institute for Endocrinology, Reproduction and Metabolism, Vrije Universiteit Medical Centre, 1081 AV Amsterdam, The Netherlands. Email: j.mcdonnell{at}vumc.nl
BACKGROUND: For some years, there has been a debate as to the place of the crossover trial in assisted reproduction technology (ART). We aimed to investigate whether crossover and parallel designs result in different estimates of treatment effects. METHODS: We carried out computer simulation of cohorts of patients undergoing either intra-uterine insemination (IUI) or IVF under both parallel and crossover designs, under scenarios involving censoring and carryover effects. Results of the simulation were analysed using a maximum likelihood approach. RESULTS: No relevant difference was found between the designs. The crossover design resulted in slightly more pregnancies than the parallel design. Carryover effects may slightly distort the estimates of treatment effects. Crossover and parallel designs will produce essentially the same statistical estimates of treatment effect and percentage of pregnancies. The crossover design is an acceptable design in infertility research provided the data are analysed correctly.
Key words: carryover effects/crossover design/infertility/maximum likelihood estimation/parallel design
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