Background: It has not been well established whether common indices of male condom failure are valid predictors of biologically meaningful exposure during condom use.
Methods: To address this gap, the authors compared self-reported condom malfunctions (i.e., breakage and slippage) and incorrect condom practices to 2 following objective measures of failure: prostate-specific antigen (PSA) detected in vaginal swabs collected after condom use and structural integrity of used condoms. The study, conducted in 2000–2001, evaluated 635 male condoms used by 77 women attending an outpatient, reproductive-health clinic in Birmingham, AL.
Results: Women reported breakage or slippage for 7.9% of condoms; 3.5% of postcoital swabs had moderate or high levels of PSA; and laboratory testing of used condoms revealed breaks (1.1%) and leaks (2.0%). Self-reported breakage and slippage was associated with moderate/high PSA concentrations in postcoital swabs only when the malfunctions were not accompanied by reports of corrective actions to reduce exposure (adjusted odds ratio [aOR], 6.9; 95% confidence interval [CI], 1.8–26.2). Defects observed in postcoital laboratory testing were related to PSA detection (aOR, 8.0; 95% CI, 1.5–42.6). Incorrect practices defined on the condom label were frequent, but not all types were associated with semen exposure. Furthermore, other practices not currently label-defined were associated with semen exposure: touching the tip of the penis with his hands (aOR, 6.2; 95% CI, 2.3–17.0) or with her hands (aOR, 2.8; 95% CI, 1.1–72) before donning the condom.
Conclusions: Used correctly, male condoms afforded good protection based on objective measures of failure.
Biological markers of semen exposure and laboratory assessments of condom integrity were used to evaluate condom failure and incorrect use.
From the *Division of Clinical Research and Public Health Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA; †Division of Reproductive Health, Centers for Disease Control and Prevention, Atlanta, GA; and ‡Department of Health Care Organization and Policy, University of Alabama at Birmingham, Birmingham, AL
Supported by a cooperative agreement with the Centers for Disease Control and Prevention and the Association of Schools of Public Health (S0747–18/19).
The findings and conclusions in this report are those of the authors and do not necessarily represent the official position of the Centers for Disease Control and Prevention.
Correspondence: Maria F. Gallo, PhD, DrPH, Division of Reproductive Health, 4770 Buford Highway, Mail Stop K-34, Atlanta, GA 30341–3724. E-mail: firstname.lastname@example.org.
Received for publication June 2, 2010, and accepted November 26, 2010.
Condoms are the most effective method currently available for sexually active individuals to reduce their risk of human immunodeficiency virus (HIV) infection and other sexually transmitted infections (STIs).1–3 Understanding the frequency and causes of condom failure, therefore, is critical. To date, our knowledge about the failure rate generally has come from 3 sources. First, condom manufacturers are required to meet strict product standards; the rate of defects observed in laboratory testing of batches of unused condoms cannot exceed 0.25%.4 Second, studies of condom effectiveness often collect self-reported data on condom malfunction.5 Self-reported rates of breakage and slippage during vaginal intercourse in prospective studies generally have been in the range of <1% to 6% of male latex condom uses.6–12 Third, condom failure can be assessed with biologic indicators, such as unintended pregnancy or STI, among couples who report using condoms regularly.
An estimated 2% of couples who report using male condoms correctly and consistently will have an unintended pregnancy in the first year.13 Alternatively expressed, the unintended pregnancy rate among perfect condom users is 0.02% per condom use.4 Similarly, low rates of HIV transmission observed among HIV-discordant couples reporting consistent and correct use of condoms suggest that condom failure is rare in this population.1,2 Variability in the susceptibility to pregnancy or STI, however, complicates the assessment of per-condom efficacy. For example, condom failure during the infertile days of the menstrual cycle may not result in pregnancy, thus leading to an underestimation of the failure rate.14 Likewise, the effectiveness of condoms against transmission of microorganisms can only be assessed when a condom is used with an infected partner.15
Whether these indices measure biologic exposure or mechanical failure during use of an individual condom is not well known. Such a gap in knowledge is especially troubling given assertions that condoms fail frequently in actual use.16 Recent research has tested for biologic markers of semen exposure, such as presence of prostate-specific antigen (PSA)6,7,17–21 or Y-chromosome deoxyribonucleic acid,22 in vaginal fluid collected after intercourse as evidence of condom failure. We compared self-reported condom malfunction and incorrect condom practices to 2 objective measures of semen exposure levels of PSA in postcoital swabs of vaginal fluid and the structural integrity of used condoms assessed in a laboratory setting.17
MATERIALS AND METHODS
This analysis uses data from a prospective study of the use of male and female condoms among couples at low risk for STI conducted between January 2000 and July 2001 at a reproductive-health, outpatient clinic in Birmingham, AL.18 Eligible participants were women aged ≥19 years, had a male partner with whom they had been mutually monogamous for ≥6 months, had ≥4 acts of sexual intercourse within the past 30 days, and had no history of STIs in the previous 6 months. Institutional review boards at the University of Alabama at Birmingham and the Centers for Disease Control and Prevention reviewed and approved the study protocol. Informed consent was obtained from all participants.
At the baseline visit, participants were randomly assigned to use either the female condom (n = 55) or the male latex (prelubricated) condom (n = 53). A nurse clinician instructed each participant on correct use of the condom and dispensed 10 of the assigned type. At enrollment, participants provided demographic information and sexual and reproductive histories. They were instructed to fill out a brief condom log after using each condom and to store the used condom and precoital and postcoital swabs (described below) in prelabeled bags containing desiccant. They were supposed to return the logs and condom and swab specimens to the clinic by the next business day.
After using the first 10 condoms, participants returned for a follow-up visit, completed a questionnaire, and received 10 condoms of the other type with instructions for correct usage. Participants returned to the study clinic for an exit interview after using all the condoms.
Self Reporting of Condom Failure and Incorrect Use
After each condom use, participants completed a condom log entry, consisting mainly of close-ended questions, to record self-reported condom failure and potentially related factors. Logs were supplemented by questionnaires administered at the baseline, midstudy (i.e., after the first 10 condom uses), and exit interviews. Data from the condom logs were used to construct variables for the following: (1) self-reported condom malfunctions (i.e., condom breakage or slippage evident to the user); (2) corrective actions aimed at reducing the woman's exposure to semen in the event of condom malfunction (i.e., stopping sex, using a new condom if the condom broke or slipped, or redonning the original condom if it slipped); (3) self-reported, label-defined, incorrect condom practices, which included practices defined on the condom label (i.e., penile-vaginal contact before donning, not wearing a condom throughout the entire act [including during ejaculation], not withdrawing immediately after ejaculation, or not holding the base of the condom during withdrawal); and (4) self-reported, other potentially incorrect condom practices, which were not specified on the condom label but which we considered a priori to potentially lead to semen exposure (i.e., partner's hands touching the penis tip before he donned the condom, participant's hands touching his penis tip before she donned the condom; penis tip touching the outside of the condom before it was donned).
Collection and Testing of Vaginal Specimens for PSA
Collection and testing of vaginal specimens for PSA followed procedures used in prior research.6,17–19,23,24 Women used a vaginal self-sampling device consisting of a gynecologic swab placed inside a cardboard tampon tube to protect against contamination with fluids on hands or external genitalia. Participants were instructed to take a vaginal sample immediately before and after intercourse, place the swabs in prelabeled bags with desiccant, and return them to the study clinic on the next business day. The dried swab samples were stored at room temperature before extraction in 3 mL of 0.9% saline. Extractions were stored at −80°C. Eluents later were thawed and tested for PSA with the IMx PSA immunoassay (Abbott Laboratories, Abbott Park, IL). PSA is a sensitive marker for semen in vaginal specimens with ≤1 ng of PSA per mL of eluent from swabs collected immediately after coitus considered to be inconsistent with semen exposure.23,24
From the analysis, we excluded condoms used during acts in which residual PSA was detected in the vaginal vault from previous, or recent semen exposures. First, we tested the postcoital swab. If the postcoital level of PSA indicated no semen exposure (≤1 ng/mL), the precoital swab was not tested, and the condom was included in the analysis. If the postcoital PSA was >1 ng/mL, the precoital swab was tested. If the precoital PSA level also was >1 ng/mL, we could not rule out the presence of semen in the vaginal vault before the study coital act, and therefore excluded the condom from the analysis. However, if the precoital PSA level was ≤1 ng/mL, we included the condom in the analysis.
We stratified postcoital PSA levels detected in vaginal swabs into following 4 categories: negative (≤1 ng of PSA per mL of eluent), low/equivocal (>1 but <22), moderate (≥22 but <100), and high (≥100). The cut point at 22 ng/mL is based on a study of the variability in PSA levels from duplicate vaginal fluid samples, which established that almost all test-retest differences were <22 ng/mL.17,24 Because we limit the current analysis to negative precoital PSA levels (i.e., ≤1 ng/mL), a moderate/high postcoital PSA level (≥22 ng/mL) is unlikely to be due to test-retest variability and likely indicates exposure during use of study condoms. For postcoital PSA levels <22 ng/mL, we cannot rule out exposure.24 Thus, these levels were considered low/equivocal. The cut point at 100 ng/mL represents the upper limit of detection for the IMx system; we did not use serial dilutions to quantify levels ≥100 ng/mL.
Assessment of Structural Integrity of Used Condoms
Breaks in the used condoms were identified by visual inspection and were assessed independent of self-reported functionality problems. We used a modified water leak test to assess condoms without evident breaks.17 After rinsing, condoms were suspended from a 2 × 2-inch polyvinyl chloride reducer coupling. Water (300 mL) containing methylene blue was poured into the condom, and any drop remaining on the outer surface was wiped away. After 5 minutes, the outside of the condom again was dried carefully, using a folded white laboratory tissue. After 5 more minutes, this process was repeated. Any visible blue mark on either tissue was considered evidence of a leak.
We used frequency distributions to describe the study group at baseline and measures of condom failure and incorrect use. We used logistic regression to evaluate the association between the different measures of condom failure and incorrect use and moderate/high PSA concentrations in the postcoital swab. For the analysis of simple associations, we fitted individual logistic regression models, using generalized estimating equations (specifying the exchangeable working correlation matrix) to account for multiple acts from individual women. We then fit a model with all measures of condom failure and performed manual backward elimination of factors that were not associated with moderate/high PSA results on the basis of a 2-sided test with an α of 0.05.
Although 108 women were enrolled in this study, we considered only the 77 women who used male latex condoms with their partners. These couples tested a total of 700 male condoms. We excluded 65 condoms that were from acts with a precoital swab containing >1 ng/mL of PSA. Such an elevated precoital PSA level—likely resulting from recent unprotected sexual coitus, recent condom failure, or contamination of the precoital swab—would make interpretation of postcoital PSA levels difficult. Consequently, we assessed condom failure for the remaining 635 male condoms.
Of the 77 women, 40 contributed data on 10 male condoms; the remainder reported on 9 condoms (14 women), 8 condoms (8 women); and 1 to 7 condoms (15 women). As previously reported,18 participants had a mean age of 33 years and were predominantly white (75%). Most of the participants in study group were married or cohabitating (79%) with mean relationship duration of 7.5 years and an average of 10.2 coital acts during the past month.
Frequency of Condom Failure and Incorrect Practices
Women reported condom malfunction (breakage or any slippage) for 50 (7.9%) of the condoms used (Table 1). Breakage and complete slippage occurring during coitus itself (i.e., not at the time of condom application or removal), which has been defined elsewhere as “clinical failure,”5 occurred at a rate of 3.3% (21/635). Overall, women reported taking corrective actions in response to 31 of the 50 condom malfunctions. Thus, the breakage and slippage rate for condoms where corrective actions were not employed was 3.0% (19/635). Laboratory testing of the structural integrity of the used condoms revealed 7 breaks (1.1%) and 13 leaks (2.0%). Most condoms (86.5%) were from acts with postcoital vaginal PSA concentrations of ≤1 ng/mL, which suggests that no semen exposure occurred. The remaining postcoital PSA levels were low/equivocal (10.1%), moderate (1.1%), or high (2.4%).
Participants described ≥1 incorrect practice defined on the condom label for 73.5% of the condom uses (Table 1). Not holding the condom base during withdrawal (61.3%) was the most frequently reported incorrect practice. The most common of the other potentially incorrect practices was touching the tip of the penis with his hands (16.2%) or with her hands (15.3%) before donning the condom.
Self-Reported Breakage Versus Laboratory Assessment of Defects
Breaks were confirmed by visual inspection at the laboratory in 7 of 9 used condoms for which women who reported a break; the remaining 2 had neither breaks nor leaks identified in the laboratory testing. Although laboratory testing did not reveal any additional breaks other than those also reported as malfunctions by the women, the 13 leaks found in the water leak testing were not accompanied by self-reported malfunctions.
Condom Failure by PSA Detection
Condom uses with a self-reported malfunction appeared more likely to have moderate/high PSA concentrations detected in the postcoital swab than did those without self-reported malfunctions (10.0% and 2.9%, respectively; Table 2). Four of the condom uses with a self-reported malfunction had high PSA concentrations in the postcoital swabs; all 4 of these condom uses occurred in the acts in which the woman did not report taking corrective actions to reduce exposure to semen. In the analyses of simple associations, condom uses with a self-reported malfunction accompanied with a corrective action were not associated with moderate/high PSA concentrations detected in the postcoital swabs (odds ratio [OR], 0.9; 95% confidence interval [CI], 0.1–7.1; Table 3). However, condom uses with a self-reported malfunction without corrective action were associated with the PSA outcome (OR, 8.8; 95% CI, 2.7–29.1).
Condoms with breaks and leaks identified in the laboratory appeared more likely to have moderate/high PSA concentrations detected in the postcoital swab than did those without a laboratory-identified defect (10.0% and 3.2%, respectively; Table 2). The 2 condoms with defects and high PSA concentrations were from condom uses without reports of corrective actions. In the analysis of simple association, condom uses with laboratory evidence of a break or leak were not associated with a statistically significant increase in the risk of semen exposure (OR, 3.5; 95% CI, 0.8–16.0; Table 3).
Incorrect Condom Practices by PSA Detection
Of the 585 condom uses without self-reported malfunctions, 17 had moderate/high PSA concentrations in the postcoital swabs. All 17 of these swabs were from acts in which the woman reported ≥1 incorrect condom practice (Table 4). Fifteen percent of acts in which the participant reported not using the condom throughout the entire act (including during ejaculation) had moderate/high PSA concentrations in the postcoital swabs; in comparison, only 2.0% of acts in which participants did not report this incorrect practice had the PSA outcome. This incorrect practice was associated with the PSA outcome in the analysis of simple associations (Table 3).
Among the practices not defined on the condom label that we a priori considered as potentially leading to semen exposure, only 1 practice was significantly associated with the PSA outcome. Acts in which women reported that their partner touched the penis tip before condom application were more likely to have moderate/high postcoital PSA than acts in which the practice was not reported (9.1% and 1.6%, respectively; Table 4).
Multiple Regression Analysis
In multivariable analyses, having at least 1 malfunction during the act that was not accompanied by a corrective action was associated with moderate/high PSA concentrations in the postcoital swab (adjusted OR [aOR], 6.9; 95% CI, 1.8–26.2; Table 3). Malfunctions with corrective actions were not associated with the PSA outcome. Laboratory-identified breaks or leaks were related to moderate/high PSA concentrations (aOR, 8.0; 95% CI, 1.5–42.6).
Two of the incorrect practices defined on condom labels were associated with the PSA outcome in the adjusted model: not using the condom throughout the entire act (including during ejaculation) (aOR, 6.2; 95% CI, 2.5–15.1) and not immediately withdrawing after ejaculation (aOR, 4.0; 95% CI, 1.4–11.5; Table 3). Penile-vaginal contact before donning and not holding the base during withdrawal did not appear to increase the risk of semen exposure.
Among the other potentially incorrect practices not defined on condom labels, touching the tip of the penis with his hands (aOR, 6.2; 95% CI, 2.3–17.0) or with her hands (aOR, 2.8; 95% CI, 1.1–72) before donning the condom appeared to increase the risk of semen exposure (Table 3). The penis tip touching the outside of the condom before its application was not related to the PSA outcome.
Women reported breakage or slippage for 7.9% of male condom uses, which appears to be higher than rates of self-reported malfunctions in other prospective studies of latex male condoms.6–12 Several of the prior studies, though, only included clinical failures (e.g., breakages and complete slippages that occurred during coitus);8–10 the corresponding rate of clinical failures in the current study was 3.3%. Few of the used condoms (3.1%) had breaks or leaks detected during postcoital laboratory testing of their structural integrity. The rate of semen exposure, as evidenced by the detection of moderate or high PSA levels in vaginal swabs collected immediately after condom-protected coitus, was 3.5%. Thus, the 2 objective measures (i.e., laboratory assessment of defects and postcoital PSA in vaginal swabs) resulted in similar rates of condom failure, although the rates based on self-reported data were substantially higher.
Women who reported breakage or any slippage that was not accompanied by corrective actions (i.e., stopping sex, using a new condom if the condom broke or slipped, or redonning the original condom if it slipped) were more likely to have moderate/high PSA detected in the postcoital vaginal swab. In contrast, self-reported malfunctions accompanied by corrective actions did not appear to be related to the PSA outcome. This suggests that women might be able to take steps to limit their exposure to semen after an identified malfunction, a finding that is consistent with prior research.20 Future studies should account for these corrective actions; otherwise, a strong association between self-reported malfunctions and objective measures of semen exposure could be diluted or masked completely.
As shown in prior studies,25–28 reports of incorrect practices as specified in the written instructions for condoms were common. More postcoital swabs with moderate/high PSA outcomes were associated with acts in which the woman reported incorrect practices than acts in which she reported condom malfunctions. Not all of the incorrect practices, though, appeared to result in semen exposure. Not holding the base of condom during withdrawal was the most frequent incorrect practice (reported in 61% of condom uses), but was not associated with moderate/high PSA concentrations in the postcoital swab. Likewise, penile-vaginal contact before donning the condom did not appear to be related to the PSA outcome. Because PSA is secreted by the prostate gland into the urethra during ejaculation, penile-vaginal contact before donning the condom might not be expected to lead to PSA detection in postcoital swabs. However, reducing exposure to preejaculation fluid is important given its role as a potential vector for HIV transmission.29,30 Women who reported not using the condom throughout the entire act (including during ejaculation) or not immediately withdrawing after ejaculation were more likely to have the PSA outcome than women who did not report these practices.
In addition to the incorrect practices defined on the condom label, we found that contact between either the partner's or the participant's hands and the penis tip before the condom was donned, was associated with moderate/high PSA concentrations in the postcoital swab. Interventions to improve the correct use of condoms should focus on the practices likely to lead to exposure to semen or pathogens. Future studies should confirm the specific incorrect practices that place women at increased risk of exposure, and the incorrect practices specified on the condom label may need to be modified or expanded upon.
Although the study design allowed us to detect female exposure to semen, we could not assess male exposure to cervical or vaginal secretions. Another study limitation is that an unknown number of low/equivocal PSA results could be attributable solely to sampling variability. Although postcoital PSA levels >22 ng/mL following precoital levels of ≤1 ng/mL are almost certainly the consequence of new exposure to semen, postcoital levels below 22 ng/mL could either exceed corresponding precoital levels by chance alone or could result from new exposure.17,24 Thus, we do not know the proportion of low/equivocal PSA levels found in postcoital swabs that represent semen exposure during the study act. Furthermore, the sensitive test for PSA used in this study can detect exposure to minute amounts of antigen, which have unknown biologic significance in terms of risk of pregnancy or STI.
Finally, the observed failure rates may not be generalizable to other populations. Condom failure could be influenced by numerous factors, including condom age,31 the use of oil-based lubricants,32,33 penis size,34 the use of phosphodiesterase Type 5 inhibitor (PDE5i) drugs (used as treatment for erectile dysfunction),35 alcohol and other substance use,36 and user experience and techniques.37–39 The failure rate experienced by the women who self-selected into the current study, in which they were supplied with new condoms and were counseled on proper condom use, might be lower than that of other populations.
The major strength of the current study is its design. Detailed questionnaire data on condom failure and incorrect use were coupled with rigorous testing of postcoital vaginal swabs for PSA and used condoms for structural defects. Together, these 3 sources of data provide insights into condom failure that would not have been detected using conventional study designs.
In summary, we found low rates of condom failure using the 2 objective measures of condom failure and higher rates when measured with self-reported malfunctions. In the event of breakage or slippage, acts in which women reported steps to prevent exposure to semen led to less semen exposure than those without these steps. Participants frequently reported label-defined incorrect condom practices, of which failure to use the condom for the entire act and not immediately withdrawing after ejaculation were associated with semen exposure. Furthermore, additional condom practices not defined as incorrect on the condom label were associated with semen exposure. Study findings underscore the need for educational messages that emphasize the importance of reducing user errors and implementing corrective actions when condoms break or slip. Overall, the low condom failure rates observed reinforce the public health message that condoms are highly effective in preventing semen exposure when used correctly.
1. National Institute of Allergy and Infectious Diseases. Workshop Summary: Scientific Evidence on Condom Effectiveness for Sexually Transmitted Disease (STD) Prevention
. Bethesda, MD: National Institutes of Health, National Institute of Allergy and Infectious Diseases, 2001.
2. Weller S, Davis K. Condom effectiveness in reducing heterosexual HIV transmission. Cochrane Database Syst Rev 2002:CD003255.
3. Holmes KK, Levine R, Weaver M. Effectiveness of condoms in preventing sexually transmitted infections. Bull World Health Organ 2004; 82:454–461.
4. Warner DL, Hatcher RA. Male condoms. In: Hatcher RA, Trussell J, Stewart F, et al, eds. Contraceptive Technology, 18th ed. New York, NY: Ardent, 2004:331–353.
5. Steiner M, Trussell J, Glover L, et al. Standardized protocols for condom breakage and slippage trials: A proposal. Am J Public Health 1994; 84:1897–1900.
6. Galvao LW, Oliveira LC, Diaz J, et al. Effectiveness of female and male condoms in preventing exposure to semen during vaginal intercourse: A randomized trial. Contraception 2005; 71:130–136.
7. Walsh TL, Frezieres RG, Peacock K, et al. Effectiveness of the male latex condom: Combined results for three popular condom brands used as controls in randomized clinical trials. Contraception 2004; 70:407–413.
8. Potter WD, de Villemeur M. Clinical breakage, slippage and acceptability of a new commercial polyurethane condom: A randomized, controlled study. Contraception 2003; 68:39–45.
9. Steiner MJ, Dominik R, Rountree RW, et al. Contraceptive effectiveness of a polyurethane condom and a latex condom: A randomized controlled trial. Obstet Gynecol 2003; 101:539–547.
10. Cook L, Nanda K, Taylor D. Randomized crossover trial comparing the eZ.on plastic condom and a latex condom. Contraception 2001; 63:25–31.
11. Callahan M, Mauck C, Taylor D, et al. Comparative evaluation of three Tactylon(TM) condoms and a latex condom during vaginal intercourse: Breakage and slippage. Contraception 2000; 61:205–215.
12. Frezieres RG, Walsh TL. Acceptability evaluation of a natural rubber latex, a polyurethane, and a new non-latex condom. Contraception 2000; 61:369–377.
13. Trussell J. Contraceptive efficacy. In: Hatcher RA, Trussell J, Stewart F, et al, eds. Contraceptive Technology, 18th ed. New York, NY: Ardent, 2004:773–845.
14. Stanford JB, Dunson DB. Effects of sexual intercourse patterns in time to pregnancy studies. Am J Epidemiol 2007; 165:1088–1095.
15. Warner L, Stone KM, Macaluso M, et al. Condom use and risk of gonorrhea and chlamydia: A systematic review of design and measurement factors assessed in epidemiologic studies. Sex Transm Dis 2006; 33:36–51.
16. Fitch JT, McIlhaney JS, Adam MB, et al. Sex, Condoms, and STDs: What We Now Know. Austin, TX: The Medical Institute for Sexual Health, 2002.
17. Macaluso M, Lawson ML, Hortin G, et al. Efficacy of the female condom as a barrier to semen during intercourse. Am J Epidemiol 2003; 157:289–297.
18. Macaluso M, Blackwell R, Jamieson DJ, et al. Efficacy of the male latex condom and of the female polyurethane condom as barriers to semen during intercourse: A randomized clinical trial. Am J Epidemiol 2007; 166:88–96.
19. Bahamondes L, Diaz J, Marchi NM, et al. Prostate-specific antigen in vaginal fluid after exposure to known amounts of semen and after condom use: Comparison of self-collected and nurse-collected samples. Hum Reprod 2008; 23:2444–2451.
20. Walsh TL, Frezieres RG, Peacock K, et al. Use of prostate-specific antigen (PSA) to measure semen exposure resulting from male condom failures: Implications for contraceptive efficacy and the prevention of sexually transmitted disease. Contraception 2003; 67:139–150.
21. Walsh TL, Frezieres RG, Nelson AL, et al. Evaluation of prostate-specific antigen as a quantifiable indicator of condom failure in clinical trials. Contraception 1999; 60:289–298.
22. Ghanem KG, Melendez JH, McNeil-Solis C, et al. Condom use and vaginal Y-chromosome detection: The specificity of a potential biomarker. Sex Transm Dis 2007; 34:620–623.
23. Lawson ML, Macaluso M, Bloom A, et al. Objective markers of condom failure. Sex Transm Dis 1998; 25:427–432.
24. Macaluso M, Lawson L, Akers R, et al. Prostate-specific antigen in vaginal fluid as a biologic marker of condom failure. Contraception 1999; 59:195–201.
25. Warner L, Newman DR, Kamb ML, et al. Problems with condom use among patients attending sexually transmitted disease clinics: Prevalence, predictors, and relation to incident gonorrhea and chlamydia. Am J Epidemiol 2008; 167:341–349.
26. Crosby R, Sanders S, Yarber WL, et al. Condom-use errors and problems: A neglected aspect of studies assessing condom effectiveness. Am J Prev Med 2003; 24:367–370.
27. Crosby RA, Sanders SA, Yarber WL, et al. Condom use errors and problems among college men. Sex Transm Dis 2002; 29:552–557.
28. de Visser RO, Smith AM. When always isn't enough: Implications of the late application of condoms for the validity and reliability of self-reported condom use. AIDS Care 2000; 12:221–224.
29. Ilaria G, Jacobs JL, Polsky B, et al. Detection of HIV-1 DNA sequences in pre-ejaculatory fluid. Lancet 1992; 340:1469.
30. Pudney J, Oneta M, Mayer K, et al. Pre-ejaculatory fluid as potential vector for sexual transmission of HIV-1. Lancet 1992; 340:1470.
31. Steiner M, Foldesy R, Cole D, et al. Study to determine the correlation between condom breakage in human use and laboratory test results. Contraception 1992; 46:279–288.
32. Steiner M, Piedrahita C, Glover L, et al. The impact of lubricants on latex condoms during vaginal intercourse. Int J STD AIDS 1994; 5:29–36.
33. Voeller B, Coulson AH, Bernstein GS, et al. Mineral oil lubricants cause rapid deterioration of latex condoms. Contraception 1989; 39:95–102.
34. Smith AM, Jolley D, Hocking J, et al. Does penis size influence condom slippage and breakage? Int J STD AIDS 1998; 9:444–447.
35. Crosby R, Yarber WL, Sanders SA, et al. Is phosphodiesterase type 5 inhibitor use associated with condom breakage? Sex Transm Infect 2009; 85:404–405.
36. Kalichman SC, Simbayi LC, Cain D, et al. Condom failure among men receiving sexually transmissible infection clinic services, Cape Town, South Africa. Sex Health 2009; 6:300–304.
37. Albert AE, Warner DL, Hatcher RA, et al. Condom use among female commercial sex workers in Nevada's legal brothels. Am J Public Health 1995; 85:1514–1520.
38. Spruyt A, Steiner MJ, Joanis C, et al. Identifying condom users at risk for breakage and slippage: Findings from three international sites. Am J Public Health 1998; 88:239–244.
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39. Macaluso M, Kelaghan J, Artz L, et al. Mechanical failure of the latex condom in a cohort of women at high STD risk. Sex Transm Dis 1999; 26:450–458.