Analysis of contraceptive failure data in intrauterine device studies. Modern competing risks approach.

The life table method used heretofore in case of intrauterine device (IUD) failure data requires grouping of data into intervals. If the termination times are recorded exactly along with the reason of termination, grouping of data results in some loss of information. Modern competing risks techniques are suggested here for the exact IUD failure data. The uses of cumulative incidence functions, which are essentially the quantity given by Potter's net rate, and cause-specific hazard rates are stressed. Also, this paper focuses on the flaws of life table estimates of net and gross rates, which have been widely used during the past three decades in the analysis of contraceptive failures. The methods suggested in this paper can be used in any other situation where the failure times and reasons of failure are recorded.