Association Between Sexually Transmitted Diseases and Young Adults' Self-reported Abstinence

A recent analysis by DiClemente and colleagues of data from a nationally-representative sample of young adults in the US found discordance between reports of sexual behavior and sexually transmitted infection (STI) status.1 Specifically, >10% of those with a positive nucleic acid amplification test for nonviral STIs reported no sex in the prior 12 months. About 6% of those who tested positive reported never having had penile-vaginal sex. Note that these figures do not provide the overall rate of under-reporting of recent sex. Only individuals with an infected partner are at risk of infection and, thus, could have discordant self-reports and STI test results. Given the discrepancy in self-reporting of sexual activity, the authors conclude that clinicians should test all young people for prevalent STIs rather than screen based on sexual history.

These clinical findings further corroborate recent research evaluating the validity of self-reported sexual behavior among adult women based on the identification of a biological marker of semen exposure in vaginal fluid, most notably, prostate-specific antigen (PSA) or spermatozoa Y-chromosome sequences.2 PSA, a protein found in high concentrations in seminal plasma, is detectable in vaginal fluid for up to 48 hours following exposure to semen.3-6 Thus, the detection of PSA in vaginal swabs provides an objective measure of a woman’s recent exposure to semen. Unlike STIs, PSA can be used to identify a greater proportion of acts of unprotected sex (i.e., not just acts occurring with an infected partner in which the infection was transmitted). That said, because PSA begins to clear from the vagina almost immediately post-exposure and generally clears completely within 48 hours, the proportion testing positive for PSA should be interpreted as the lower bound of the proportion who were exposed to semen in past 48 hours.

Substantial proportions of female sex workers in Guinea (36%),7 Kenya (11%)8 and Madagascar (29%)9 who reported no unprotected sex in the past 48 hours tested positive for PSA. The detection of PSA also revealed substantial, apparent under-reporting of recent unprotected sex among low- risk women in Zimbabwe.10 Finally, an analysis comparing data from two studies conducted among women in Alabama and Brazil found similar rates of PSA detection in the two populations but different rates of problems reported with condom use.11 This finding suggests that reports of condom problems also might not be valid.

While none of these outcomes (PSA detection, STI diagnoses or self- reports of unprotected sex) are likely to capture all cases of recent exposure to semen, PSA detection could be expected to be a less biased measure. That is, the ability to detect PSA among those with recent semen exposure is unlikely to be differential with respect to factors such as participant characteristics or behaviors. In contrast, only participants who have an infected partner could have a STI diagnosis, and among participants who had recent semen exposure, those who elect to report engaging in unprotected sex might be very different than those who do not report this behavior. For example, evaluations of condom promotion interventions or abstinence-only curricula often rely on self-reported outcomes. However, the intervention itself could affect the reporting of the outcome; social desirability bias could cause participants receiving the intervention to under-report engaging in unprotected sex to a greater degree than participants in the control arm, which could lead to erroneous conclusions regarding the intervention’s effectiveness.

Self-reported data on sexual behavior have long been a cornerstone of HIV/STI research and are widely employed. In another recent report on the validity of self-reports of condom use, Lipovsek et al. wrote: “The general consensus is that the reliability and validity of self-reporting is questionable; but there is also agreement that it is, by and large, the only feasible way to measure sexual behaviors.”12 The report by DiClemente and colleagues adds to a body of evidence demonstrating that other methods do exist for improving measurement of sexual behavior where self reports considered alone might not be sufficiently valid.

Maria F. Gallo,* Markus J. Steiner,** Lee Warner,* Marcia M. Hobbs,† Denise J. Jamieson,* Maurizio Macaluso‡

*Division of Reproductive Health, Centers for Disease Control and Prevention **Clinical Sciences Division, FHI †Departments of Medicine and Microbiology & Immunology, University of North Carolina ‡ Division of Biostatistics and Epidemiology, Cincinnati Children's Hospital Medical Center The findings and conclusions in this letter are those of the authors and do not necessarily represent the official views of the Centers for Disease Control and Prevention.

References

1. Diclemente RJ, Sales JM, Danner F, et al. Association between sexually transmitted diseases and young adults' self-reported abstinence. Pediatrics. 2011 Jan 3 [Epub ahead of print]

2. Mauck CK, Doncel GF, Biomarkers of Semen Exposure Clinical Working Group. Biomarkers of semen in the vagina: applications in clinical trials of contraception and prevention of sexually transmitted pathogens including HIV. Contraception. 2007;75(6):407–419

3. Graves HC, Sensabaugh GF, Blake ET. Postcoital detection of a male -specific semen protein. Application to the investigation of rape. N Engl J Med. 1985;312(6):338–343

4. Kamenev L, Leclercq M, Francois-Gerard C. An enzyme immunoassay for prostate-specific p30 antigen detection in the postcoital vaginal tract. J Forensic Sci Soc. 1989;29(4):233–241

5. Lawson ML, Maculuso M, Bloom A, et al. Objective markers of condom failure. Sex Transm Dis. 1998;25(8):427–432

6. Macaluso M, Lawson L, Akers R, et al. Prostate-specific antigen in vaginal fluid as a biologic marker of condom failure. Contraception. 1999;59(3):195–201

7. Aho J, Koushik A, Diakité SL, et al. Biological validation of self -reported condom use among sex workers in Guinea. AIDS Behav. 2010;14(6):1287–1293

8. Gallo MF, Behets FM, Steiner MJ, et al. Validity of self-reported ‘safe sex’ among female sex workers in Mombasa, Kenya—PSA analysis. Int J STD AIDS. 2007;18(1):33–38

9. Gallo MF, Behets FM, Steiner MJ, et al. Prostate-specific antigen to ascertain reliability of self-reported coital exposure to semen. Sex Transm Dis. 2006;33(8):476–479

10. Minnis AM, Steiner MJ, Gallo MF, et al. Biomarker validation of reports of recent sexual activity: results of a randomized controlled study in Zimbabwe. Am J Epidemiol. 2009;170(7):918–924

11. Chen, MP, Macaluso M, Blackwell R, et al. Self-reported mechanical problems during condom use and semen exposure. Comparison of two randomized trials in the United States of America and Brazil. Sex Transm Dis. 2007;34(8):557–562

12. Lipovsek V, Longfield K, Buszin J. Can follow-up study questions about correct and consistent condom use reduce respondent over-reporting among groups at high risk? An analysis of datasets from six countries. Reprod Health. 2010:7(9)

Conflict of Interest:

None declared