Participant characteristics associated with withdrawal from a large randomized trial of spermicide effectiveness
1 Family Health International, Research Triangle Park, NC, USA
2 National Institute of Child Health and Human Development, Rockville, MD, USA
3 Department of Obstetrics and Gynecology and Center for Clinical Epidemiology and Biostatistics, University of Pennsylvania Medical Center, Philadelphia, PA, USA
4 Department of Reproductive Medicine, Johns Hopkins Community Physicians, Baltimore, MD, USA
5 University of Pittsburgh and the Magee-Womens Research Institute, Pittsburgh, PA, USA
6 Department of, Baylor College of Medicine, Houston, TX, USA
7 Department of Obstetrics and Gynecology, New York University School of Medicine, New York, NY, USA
8 Minneapolis Medical Research Foundation, Hennepin County Medical Center, Minneapolis, MN, USA (Current affiliation: Department of Obstetrics and Gynecology, University of Oklahoma College of Medicine, Tulsa, OK, USA)
9 Department of Obstetrics and Gynecology, The University of Texas Health Science Center at San Antonio, San Antonio, TX, USA
10 Vermont Women's Choice Program of Planned Parenthood, Burlington, VT, USA
11 Current affiliation: University of Vermont College of Medicine, Burlington, VT, USA
12 Department of Obstetrics and Gynecology, University of Alabama at Birmingham, Birmingham, AL, USA
BMC Medical Research Methodology 2004, 4:23 doi:10.1186/1471-2288-4-23Published: 1 October 2004
In most recent large efficacy trials of barrier contraceptive methods, a high proportion of participants withdrew before the intended end of follow-up. The objective of this analysis was to explore characteristics of participants who failed to complete seven months of planned participation in a trial of spermicide efficacy.
Trial participants were expected to use the assigned spermicide for contraception for 7 months or until pregnancy occurred. In bivariable and multivariable analyses, we assessed the associations between failure to complete the trial and 17 pre-specified baseline characteristics. In addition, among women who participated for at least 6 weeks, we evaluated the relationships between failure to complete, various features of their first 6 weeks of experience with the spermicide, and characteristics of the study centers and population.
Of the 1514 participants in this analysis, 635 (42%) failed to complete the study for reasons other than pregnancy. Women were significantly less likely to complete if they were younger or unmarried, had intercourse at least 8 times per month, or were enrolled at a university center or at a center that enrolled fewer than 4 participants per month. Noncompliance with study procedures in the first 6 weeks was also associated with subsequent early withdrawal, but dissatisfaction with the spermicide was not. However, many participants without these risk factors withdrew early.
Failure to complete is a major problem in barrier method trials that seriously compromises the interpretation of results. Targeting retention efforts at women at high risk for early withdrawal is not likely to address the problem sufficiently.