American Journal of Epidemiology Advance Access originally published online on August 24, 2005
American Journal of Epidemiology 2005 162(7):706; doi:10.1093/aje/kwi266
American Journal of Epidemiology Copyright © 2005 by the Johns Hopkins Bloomberg School of Public Health All rights reserved
HOBBS ET AL. REPLY
Marcia M. Hobbs1,2,
Markus J. Steiner3,
Paul J. Feldblum3 and
Nancy Padian4,5,6
1 Department of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
2 Department of Microbiology and Immunology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
3 Family Health International, Research Triangle Park, NC 27709
4 AIDS Research Institute, University of California, San Francisco, San Francisco, CA 94105
5 Center for Reproductive Health Research and Policy, Department of Obstetrics, Gynecology, and Reproductive Sciences, University of California, San Francisco, San Francisco, CA 94143
6 Department of Epidemiology and Public Health Biology, University of California, Berkeley, Berkeley, CA 94720
We acknowledge the concerns of Drs. Zaviacic and Ablin (1
) regarding the use of prostate-specific antigen (PSA) in vaginal secretions as a potential marker of semen exposure in studies of condom effectiveness (2–4). As they noted, despite its name, PSA is not strictly male prostate specific. In addition to the potential for detecting PSA in the "female prostate" and serum of women mentioned by Zaviacic and Ablin, Lövgren et al. (5) detected PSA in amniotic fluid from 84 percent of 43 pregnant women (range: 0.06–8.98 ng PSA/ml of amniotic fluid) and in 64 percent of 25 breast milk samples (range: 0.23–2,070 ng PSA/ml of breast milk). In addition, Schmidt et al. (6) detected PSA in urine from 11 percent of 217 women aged 18–74 years (mean concentration: 0.29, range: 0.12–1.06 ng PSA/ml of urine).
We do not dispute that PSA can be found in normal, healthy women. However, it is important to recognize that the concentrations of PSA in the samples mentioned above are extremely low compared with concentrations in semen, which range from 200,000 ng PSA/ml to 5,000,000 ng PSA/ml (7), over 2,000 times the highest concentration found in female sources. Among the few cases with detectable PSA in women's urine, concentrations are already at or below the threshold considered positive for vaginal fluid levels indicating recent semen exposure (>1 ng PSA/ml from a 3-ml vaginal swab eluate). Even after exposure to the very high concentrations of PSA in semen, dilution in the vagina results in over 500-fold lower concentrations immediately after exposure, and 97 percent of vaginal fluid specimen concentrations are below 1 ng PSA/ml 48 hours later (8). Despite identification of PSA by immunochemical staining in secretory cells of Skene's gland tissue sections, sexual activity does not result in elevated PSA levels in vaginal fluid in the absence of semen exposure, as evidenced by very recent studies measuring PSA in vaginal swabs from female sex workers in which most of the specimens were negative (Maria Gallo, personal communication).
Thus, female sources of low concentrations of PSA do not invalidate its use as an appropriate and reliable marker of a woman's recent vaginal exposure to semen and a potential indicator of the effectiveness of condoms.
 |
ACKNOWLEDGMENTS
|
|---|
Conflict of interest: none declared.
|
References
|
|---|
- Zaviacic M, Ablin RJ. The use of prostate-specific antigen as a criterion for condom effectiveness. (Letter). Am J Epidemiol 2005;162:704–5.[Free Full Text]
- Macaluso M, Lawson ML, Hortin G, et al. Efficacy of the female condom as a barrier to semen during intercourse. Am J Epidemiol 2003;157:289–97.[Abstract/Free Full Text]
- Steiner MJ, Feldblum PJ, Padian N. Invited commentary: "Condom effectiveness—will prostate-specific antigen shed new light on this perplexing problem?" Am J Epidemiol 2003;157:298–300.[Free Full Text]
- Lawson ML, Macaluso M, Duerr A, et al. Partner characteristics, intensity of the intercourse, and semen exposure during use of the female condom. Am J Epidemiol 2003;157:282–8.[Abstract/Free Full Text]
- Lövgren J, Valtonen-Andre C, Marsal K, et al. Measurement of prostate-specific antigen and human glandular kallikrein 2 in different body fluids. J Androl 1999;20:348–55.[Abstract/Free Full Text]
- Schmidt S, Franke M, Lehmann J, et al. Prostate-specific antigen in female urine: a prospective study involving 217 women. Urology 2001;57:717–20.[CrossRef][Web of Science][Medline]
- Hochmeister MN, Budowle B, Rudin O, et al. Evaluation of prostate-specific antigen (PSA) membrane test assays for the forensic identification of seminal fluid. J Forensic Sci 1999;44:1057–60.[Web of Science][Medline]
- Macaluso M, Lawson L, Akers R, et al. Prostate-specific antigen in vaginal fluid as a biological marker of condom failure. Contraception 1999;59:195–201.[CrossRef][Web of Science][Medline]
CiteULike 
Connotea 
Del.icio.us What's this?
TOP
References