Sexually Transmitted Diseases:
Comparison of Sexually Transmitted Disease Prevalence by Reported Level of Condom Use Among Patients Attending an Urban Sexually Transmitted Disease Clinic
Shlay, Judith C. MD, MSPH*†‡; McClung, Melissa W. MSPH*; Patnaik, Jennifer L. MHS∥; Douglas, John M. Jr., MD*§
Departments of *Public Health and †Community Health Services, Denver Health and Hospital Authority, Denver, Colorado; the Departments of ‡Family Medicine and §Medicine, University of Colorado Health Sciences Center, Denver, Colorado; and the ∥Tri-County Health Department, Greenwood Village, Colorado
Correspondence: Judith C. Shlay, MD, MSPH, Denver Public Health, 605 Bannock St., Denver, CO 80204-4507. E-mail: jshlay@DHHA.org
Received for publication June 3, 2003, and accepted September 11, 2003.
Background: There is controversy as to the protective effect of condoms in preventing various sexually transmitted diseases (STDs).
Goal: The goal of this study was to assess the association of various levels of condom use with a variety of STD.
Study Design: We conducted a cross-sectional study of female and heterosexual male visits to an urban STD clinic between 1990 and 2001.
Methods: Prevalence rates were calculated for gonorrhea, chlamydia, trichomonas, recent-onset genital warts, first-episode herpes, and molluscum contagiosum by reported level of condom use over the past 4 months, with adjusted odds ratios (AOR) calculated by logistic regression.
Results: Among 126,220 patient visits (39% women and 61% men), condom use over the past 4 months was reported by 54%, with 38% reporting inconsistent use and 16% consistent use. Condom users reported greater sexual risk in the past 4 months than nonusers (ie, new sex partners: 63% vs. 41%, P <0.001; multiple sex partners: 60% vs. 36%, P <0.001). When all condom users were compared with nonusers, there was limited evidence of protection against specific STD. However, when the analysis was restricted to condom users, infection rates were significantly lower in consistent than inconsistent users for both men and women for gonorrhea (AOR, 0.87 and 0.71, respectfully) and chlamydia (AOR, 0.66 and 0.74, respectfully), for trichomonas in women (AOR, 0.87), and for genital herpes in men (AOR, 0.73).
Conclusions: Comparisons of STD between condom users and nonusers are confounded by greater sexual risk in users. Comparing consistent with inconsistent users reduces this confounding, revealing protection for both men and women for nonviral STD and for genital herpes for men.
CONDOMS HAVE LONG BEEN considered to be one of the most effective practical means of reducing the risk of sexually transmitted diseases (STDs) among sexually active adolescents and adults. 1–3 Male latex condoms provide a virtually impermeable barrier to a variety of STD agents in laboratory studies. 3 Because condoms cover the shaft of the penis, they should provide protection against diseases transmitted by semen and other genital secretions and, to a lesser extent, provide protection against infections transmitted by contact with skin lesions. 4 For HIV, several prospective studies conducted on discordant couples have provided convincing clinical evidence that consistent condom use is effective in preventing HIV. 5–7 For other STDs, data on effectiveness is largely based on cross-sectional studies, with some demonstrating a protective effect against a variety of STD 3,4,8–12 and others demonstrating variable protection. 13–15
Recently, the effectiveness of condoms has been challenged by a well-publicized report by the National Institutes of Health. 16 The report concluded that there was good evidence of condom effectiveness only for HIV and for gonorrhea in men, and that published data were insufficient to draw definite conclusions about the benefit of condoms for the prevention of other STDs. 16 An important feature of this report was its discussion of the significance of methodologic issues in performing valid studies on condom effectiveness, including the difficulty in determining consistency and correctness of use as well as the infection status of partners in most situations. Furthermore, other methodologic problems have been identified in regard to collecting valid data on the effectiveness of condoms in preventing STDs. These have included the possible overestimation of condom use because of social desirability, which could be especially problematic in prospective studies that advocate condom use 15,17 and the likelihood of preferential use of condoms with riskier partners, 18–20 both of which can lead to underestimates of condom benefit.
To address some of these concerns, we undertook an analysis of a large cross-sectional database of patients visiting our urban STD clinic. Following an early analysis of condoms and STD in women in which recent condom use was determined dichotomously, 13 we subsequently modified our medical record to capture various levels of condom use. Although this change was originally intended to help explore the “dose-response” benefit of condom use, we realized that it might also provide a way to compare consistent and inconsistent use among a group of patients who, by choosing to use condoms, indicated a perception of their risk of STD. This analysis describes the prevalence rates of a variety of STDs among both heterosexual men and women by different levels of condom use.
The Denver Metro Health Clinic (DMHC), the STD clinic operated by the Denver Public Health Department, offers comprehensive services for diagnosis, treatment, and prevention of STDs. Services have historically been provided to all interested persons, regardless of income or residency, with approximately 80 patients seen daily. A computerized medical record review of visits to the clinic for a new problem by women and heterosexual men who had at least one sex partner within the past 4 months was conducted for the time period from January 1, 1990, through December 31, 2001. Abstracted data included patient demographics, information on lifetime number of sexual partners, STD history, number and type of sexual partners in the past 4 months, and use of condoms and other contraceptives (for women) in the past 4 months. This study was reviewed and approved by the Colorado Multiple Institutional Review Board.
Sexually Transmitted Disease Diagnoses
Prevalence rates were calculated for 3 laboratory-confirmed nonviral STDs and 3 clinically diagnosed viral STDs. The nonviral STDs included Neisseria gonorrhoeae, which was diagnosed by culture of cervical and urethral swabs; Chlamydia trachomatis, which was diagnosed by nucleic acid amplification tests (polymerase chain reaction or strand displacement assay) of cervical swabs in women and urine in men; and Trichomonas vaginalis, which was diagnosed by detection of motile trichomonads on microscopic examination of vaginal fluid in women. The viral STDs included genital herpes, genital warts, and molluscum contagiosum. Because of the nonstandardized attempt to confirm viral STDs by laboratory evaluation, we included only clinically apparent disease diagnosed by history and genital examination by experienced clinicians. To increase the likelihood that these diagnoses represented recently acquired infections, we included only subjects with no history of the infection (for genital herpes and genital warts) and whose symptoms had only been present for ≤30 days. Data for chlamydia were available from 1996 onward, after nucleic acid amplification tests became available.
For this study, the unit of analysis was the clinic visit. Demographic and clinical variables were assessed by reported level of condom use for women and heterosexual men separately. Condom use during sexual encounters over the past 4 months was determined during the routine clinical interview through self-report and classified as 0%, 25%, 50%, 75%, or 100%. For the analysis, patients were considered to be nonusers (0%) or users (25–100%), with users further categorized as inconsistent users (25–75%) or consistent users (100%). Logistic regression modeling for each STD and for predictors of any use of condoms as well as consistent use of condoms was performed using variables found to be significant by bivariate analysis at P values <0.20 or those considered clinically relevant. Generalized estimating equations were used to account for multiple visits by an individual. SAS version 8.1 was used for all data analysis (SAS Institute Inc., Cary, NC).
Over the 12-year study period, there were 126,220 patient visits for evaluation of a new problem, 39% by women and 61% by men. These visits occurred among 75,397 individual patients (38% women and 62% men), 70% of whom had 1 visit, 15% 2 visits, 6% 3 visits, 3% 4 visits, and 5% had 5 or more visits. For women, the median age was 24.5 years (range, 11–79 years), and race/ethnicity distribution was 40% white, 31% black, 25% Hispanic, and 4% other ethnicities. For men, the median age was 27.0 years (range, 12–85 years), and race/ethnicity distribution was 35% white, 37% black, 25% Hispanic, and 3% other ethnicities. Chlamydia was the most frequently diagnosed STD for both men and women (Table 1).
The distribution of condom use by selected patient characteristics is summarized in Table 2. The majority (54.1%) of patients reported any use of condoms, with 38.1% reporting inconsistent use and 15.9% reporting consistent use. Men were more likely to report any condom use than women, although this was the result of a greater level of inconsistent use, because consistent use did not vary by gender. Among women, the level of condom use varied by whether they were using other forms of contraception, with rates of any use and consistent use lower among those using contraception. Adolescents were more likely to report any use and consistent condom use than were older patients. Finally, condom use varied markedly by ethnicity. Blacks were more likely to report any condom use than were the other groups, although this was largely the result of a greater level of inconsistent use. Whites were more likely to report consistent use and Hispanics were less likely to either report any or consistent use than either of the other groups.
Table 3 summarizes sexual risk behavior among condom use groups. Patients reporting any use of condoms were more likely to report >10 lifetime sex partners than nonusers (57.5% vs. 50.6%, P <0.001), although there was no difference in the rate of past STD. There were even greater differences between users and nonusers in the reporting of recent sexual risk. Condom users were 50% more likely to report new sex partners (62.5% vs. 41.2%, P <0.001) and 70% more likely to report multiple sex partners (59.9% vs. 35.6%, P <0.001) in the past 4 months than nonusers. Among condom users, recent sexual risk was greater for inconsistent than consistent users as assessed by the proportion with new sex partners (63.8% vs. 59.0%, P <0.001) and multiple sex partners (63.9% vs. 50.1%, P <0.001).
Demographic and risk behavior variables associated with any use versus nonuse of condoms and consistent versus inconsistent use were compared among men and women by logistic regression (Table 4). Any use of condoms was most strongly associated in men with younger age, non-Hispanic ethnicity, and recent sexual risk behavior (ie, new sex partner, multiple sex partners). A weaker association was found with having a prior STD. Similar patterns were seen for any use of condoms in women with the exception that those who reported using contraception were significantly less likely to use condoms and were more likely to have >10 lifetime sex partners.
Consistent use of condoms in men was associated with non-Hispanic ethnicity (Table 4). However, the association of consistent condom use with recent sexual risk varied. On the one hand, consistent users were more likely to report new sex partners, have a history of STDs, and have ≤10 lifetime sex partners; on the other hand, they were less likely to report multiple sex partners. Among women, consistent condom use was associated with older age, white race, and with not using another form of contraception. Similarly, the association with recent sexual risk varied as it did for men in that consistent users were more likely to report a new sex partner and less likely to report multiple sex partners than were inconsistent users (Table 4).
Table 5 compares the rates of STD by condom use categories, controlling for demographic and risk behavior variables, by logistic regression. Among men, when all condom users were compared with nonusers, condom users had lower rates of genital herpes (adjusted odds ratio [AOR], 0.79; 95% confidence interval [CI], 0.71–0.89), but slightly higher rates of genital warts (AOR, 1.17; 95% CI, 1.04–1.31) with no significant differences for the other STDs. In contrast, among those men who used condoms, consistent users had significantly lower rates of gonorrhea (AOR, 0.87; 95% CI, 0.81–0.94), chlamydia (AOR, 0.66; 95% CI, 0.60–0.73), and genital herpes (AOR, 0.73; 95% CI, 0.61–0.88) than inconsistent users. Similar patterns were seen for women. Compared with nonusers, condom users had similar rates of STDs except for lower rates of gonorrhea (OR, 0.89; 95% CI, 0.83–0.96) and higher rates for chlamydia (AOR, 1.18; 95% CI, 1.07–1.30). However, among women using condoms, consistent users had significantly lower rates of gonorrhea (OR, 0.71; 95% CI, 0.63–0.80), chlamydia (OR, 0.74; 95% CI, 0.65–0.84), and trichomoniasis (OR, 0.87; 95% CI, 0.78–0.97) than inconsistent users. In addition, for women, there was a trend toward a lower rate of genital herpes, as seen for men, although this difference was not statistically significant (P = 0.09).
This large retrospective cross-sectional study of subjects attending an STD clinic assessed the field effectiveness of condoms in the prevention of a variety of nonviral and viral STDs in both men and women, and it highlights many of the difficulties involved in determining the protection provided by condoms. When all persons reporting condom use were compared with persons not using condoms, there was limited evidence of protection (only genital herpes for men and gonorrhea for women), with some suggestion of an actual increase in rates of STDs (genital warts in men and chlamydia for women). However, persons choosing to use condoms did so in the context of greater sexual risk than nonusers, with 50% more subjects reporting new sex partners and 70% more subjects reporting multiple partners, supporting the observation that condom use is a marker for sexual partnerships with greater risks of STD transmission. 17 Given this differential sexual risk and the likely associated risk in actual exposure to STD, the more relevant comparison is within the condom use group, between those who used them consistently and those who did not. In this context, a consistent protective effect was seen for nonviral STD, as well as some evidence of protection for genital herpes. Among men, not only did we find the previously demonstrated protection against gonorrhea, 16,21 but also found an even greater level of protection for chlamydia and genital herpes. Among women, we were able to demonstrate effectiveness against both gonorrhea and chlamydia at levels similar to that for men; protection against trichomonas, previously only demonstrated for female condoms 22; and a trend toward protection against genital herpes.
The availability of only routinely collected clinical data precluded a detailed understanding of the factors leading to the decision to use condoms in sexual partnerships. Our analysis indicated that any condom use was significantly more common among blacks and less common among Hispanics than other racial/ethnic groups. However, the higher rates among blacks were largely limited to inconsistent rather than consistent use. The reason for these differences by race/ethnicity are unclear, but could have important implications for STD/HIV prevention strategies and should be assessed in future studies evaluating condom use practices. Our study also demonstrated that women were less likely to use condoms if they reported using contraception. Although previous studies on condom use for prevention of pregnancy and STDs have been conflicting, 23–25 for many women, dual protection is not motivated by a desire to prevent both pregnancy and STDs, but rather a desire to have a “back-up” for pregnancy prevention. 26–29 Only when women perceive themselves to be directly at risk for acquiring an STD are they likely to use condoms for STD prevention. 30–32 Although promoting the use of condoms could raise issues of trust within ongoing relationships, counseling messages, which promote both the contraceptive and STD prevention benefit of consistent condom use, could make women more willing to use them as part of a dual-method strategy. 33
Although difficulty in defining incident infection and incubation period for viral STDs reduces precision, the consistency of condom effectiveness was less for viral than nonviral STDs. The viral STD for which we saw the greatest benefit was genital herpes. For men, the level of protection was statistically significant and was similar to that seen for gonorrhea and chlamydia, whereas for women, there was a trend toward benefit, which was not statistically significant (P = 0.09). These results differ from a recent report by Wald of a study among discordant couples, which found a protective effect of condoms for women but not men, 34 although a preliminary report of a different prospective study by the same group found similar benefit for both men and women. 35 In contrast, we saw no significant protection for either genital warts or molluscum contagiosum for either men or women. Because these epitheliotropic viruses are more likely to involve genital skin not consistently covered by male condoms, these results are not surprising. Furthermore, the location of these lesions could make them more susceptible to errors of condom use such as complete or partial slippage than genital herpes or the nonviral STDs. Of note, a recent metaanalysis evaluating condoms for the prevention of genital human papillomavirus (HPV) infection found very little protection from infection as detected by HPV DNA but some suggestion of benefit for the prevention of HPV-related disease (eg, genital warts, cervical intraepithelial neoplasia, and cervical cancer). 36
Although rates of nonviral STD were consistently lower in consistent than inconsistent users, the level of demonstrated protection (13–30%) is admittedly modest, even if statistically significant. In this regard, several aspects of our study design that likely led to underestimates of the protective effect of condoms should be pointed out. First, condom use was established retrospectively over an extended time period (4 months) and during a routine clinical encounter with the use of a single question, creating opportunities for both recall bias and social desirability to inflate estimates of use. Second, we elicited only limited information about sexual risks. Although condom users had greater levels of risks than nonusers by most measures, there was not a consistent pattern between consistent and inconsistent users. With more extensive determination of sexual risks, it is possible that consistent users would have had a greater degree of risks (and thus STD exposure) than inconsistent users. Third, the absence of knowledge of partner infection status, impossible in a study such as this and really only ethically feasible in cohort studies of couples who are discordant for infections that are not curable (eg, genital herpes 34 or HIV 5–7) underestimates condom effectiveness by including subjects in the analysis not actually exposed to STDs. The magnitude of this resulting error can be substantial, resulting in underestimates of condom effectiveness of over 50%. 37
Fourth, as a cross-sectional analysis, our study was not able to determine the timing of exposure to various STDs among our subjects. Urethral gonorrhea in men likely presents after a relatively short incubation (eg, within the 4-month timeframe of our condom use question), but chlamydia in men and gonorrhea, chlamydia, and trichomoniasis in women have poorly defined incubation periods and the potential for persistence over months. This problem could be an even more important issue for the viral STDs. Thus, some of the STDs we detected were probably acquired before the 4-month interview timeframe. Fifth, the methods we used to confirm individual STDs had variable sensitivity: highest for chlamydia (estimated sensitivity of polymerase chain reaction and strand displacement assay, 95–98%) 38 and gonorrhea (estimated sensitivity of culture, 80–95%), 38 intermediate for trichomoniasis (estimated sensitivity of microscopic examination, 50–70%), 39 and lowest for the viral STDs, which we could determine only on clinical grounds. This problem obviously underestimates ascertainment of the STD end points, although the direction of the bias it produces is difficult to determine.
A final issue is our inability to measure correctness of condom use. Condom use errors are estimated to occur in up to 8% of episodes of sexual intercourse 40 and have the potential to substantially reduce the field effectiveness of condoms. When condoms are not used correctly (ie, as a result of breakage, slippage, reuse, or starting or finishing intercourse without a condom), preliminary analysis suggests that incident STD rates are similar to those among inconsistent condom users. 19,20 Additional studies that address the impact of correctness of condom use on incident STDs are an important priority.
Despite these limitations, our study showed that, although imperfect, consistent use of condoms provides at least a partially effective approach for sexually active persons wanting to decrease their risk of a variety of STDs. Thus, although clearly not as efficacious as abstinence, or a substitute for other prevention approaches such as care in partner selection, mutual faithfulness, and screening/treatment for STDs, 41 consistent use of condoms remains an important strategy in reducing the risk of STDs among sexually active adolescents and adults.
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