A competing risk approach to the analysis of trials of alternative intra-uterine devices (IUDs) for fertility regulation

The methods of survival analysis have had a profound influence on the way t hat studies concerned with the safety and efficacy of intra-uterine devices (IUDs) for fertility control have been designed, conducted, analysed and r eported. For example, the Kaplan-Meier technique has been used to summarize the results of controlled clinical trials of alternative devices and the l ogrank test used to make any comparisons. A particular feature of IUD studi es is the large number of possible causes of failure (reasons for discontin uation of the device). These lead to considerations of competing risks, whe re in this framework, the discontinuations are considered as competing caus es of contraceptive failure. In this context, we compare the net and crude probability estimates of discontinuation rates using continuous time and ar gue for the routine use of the latter. We use data from a randomized multi- centre trial on the long-term safety and efficacy of two IUDs, TCu220C and TCu380A, for illustration. Copyright (C) 2001 John Wiley & Sons, Ltd.