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Biomarker validation of reports of recent sexual activity: results of a randomized controlled study in Zimbabwe
Global Health Sciences Literature Digest
Published March 18, 2010
Journal Article

Minnis AM, Steiner MJ, Gallo MF. Biomarker validation of reports of recent sexual activity: results of a randomized controlled study in Zimbabwe. Am J Epidemiol. 2009 Oct 1;170(7):918-24.

In Context

Accurate measures of sexual behaviors are necessary in the conduct of research regarding HIV and other sexually transmitted diseases. Study participants may report inaccurate information on their behaviors because of social desirability, poor recall, poorly worded questions, or concerns about being dropped from the study if their reported risk is low.(1) Audio computer-assisted self-interviewing (ACASI) has been used in an effort to improve the accuracy of reporting sexual behaviors. Comparisons of data collected from ACASI and face-to-face interviews (FTFI) have found higher and lower reported risk with ACASI compared to FTFI.(2)


To compare the validity of reported recent vaginal sex obtained with ACASI to the validity of reports obtained from FTFI using prostate-specific antigen (PSA) as a biomarker of semen exposure


Health clinics in Chitungwiza and Epworth, Zimbabwe

Study design

Cross-sectional, randomized study


Sexually active, HIV-negative women aged 18-49 years who were enrolled in a randomized clinical trial on the protective effects of diaphragms plus lubricant gel in decreasing susceptibility to HIV


The association among self-reported vaginal sex, condom use and biological marker of semen exposure (PSA) among women interviewed using ACASI and FTFI.


Women who participated in the clinical trial and who had not had a vaginal delivery or third-trimester stillbirth in the previous six weeks were invited to participate at the end of the clinical trial. Participants in this survey were randomized to ACASI or FTFI. Participants answered questions about their sexual activity and condom use, breakage, slippage, and spillage in the past seven days. Participants provided self-collected vaginal swabs that were air-dried and shipped to University of North Carolina, Chapel Hill, for PSA testing.

Chi-squared tests were used to compare the proportions of women who reported having vaginal sex and condom-protected vaginal sex in the past two days via ACASI with the proportions who reported those activities via FTFI. To compare self-reported behaviors with PSA test results, a 1-sided Fisher exact test was used, based on the hypothesis that ACASI would yield increased reporting of sensitive behaviors (i.e., no recent vaginal sex and vaginal sex unprotected by a condom) and thus lower the proportion of discrepant results between PSA test and FTFI.


There were 910 participants (450 ACASI and 460 FTFI). Thirty-four percent of the women reported having no vaginal sex in the past two days, and 36.4% reported using a condom for all vaginal sex acts during this period. The proportion of women who reported no vaginal sex did not vary significantly between interview modes, but the proportion who reported condom-protected sex only was lower in the ACASI group than in the FTFI group (32.7% vs. 40.0%; P=0.01).

Thirteen (12.5%) of the women interviewed with ACASI and 10 (10.9%) of the participants who tested positive for PSA reported having no vaginal sex in the previous two days (P=0.72). Seventy-one (36.2%) participants who tested positive for PSA reported condom-protected sex only, and no difference by interview mode was observed (33.7% ACASI vs. 39.1% FTFI; P=0.26). Five of these 71 participants experienced condom breakage, slippage, or semen spillage, and no difference between interview modes was observed. When these cases were removed from the analysis, the level of discordance was reduced from 48% to 45%. Among the PSA-positive participants, 7.7% (n=15) reported having no vaginal sex over the last seven days, but the small number did not permit meaningful comparisons between ACASI and FTFI.


Self-report was a poor predictor of recent sexual activity and condom use in this study, regardless of interview mode.

Quality rating

This was a good study because it included proper randomization. Although the study did not indicate if the assessor was blinded to the outcome, given the methods used, it is likely that blinding occurred. A limitation was use of a one-sided Fischer exact test.

Programmatic Implications

The high level of discrepant self-reporting in this study, regardless of interview mode, suggests a substantial degree of inaccurate reporting of sexual behavior. As such, the ability to conduct valid HIV prevention research may be limited given our current data collection methods. Discordance between self-report of sexual activity and biomarkers has been found in other studies, suggesting that this finding is real and widespread.(3, 4, 5, 6) To the extent possible, self-reported sexual behaviors should be validated using reliable bio-markers. In addition, on-going research to further understand the factors that contribute to and that may minimize inaccurate reporting of sexual behaviors should be pursued.


  1. Weinhardt LS, Forsyth AD, Carey MP, et al. Reliability and validity of self-report measures of HIV-related sexual behavior: progress since 1990 and recommendations for research and practice. Arch Sex Behav. 1998;27(2):155-80.
  2. Simoes AA, Bastos FI, Moreira RI, et al. A randomized trial of audio computer and in-person interview to assess HIV risk among drug and alcohol users in Rio De Janeiro, Brazil. J Subst Abuse Treat. 2006;30(3):237-43.
  3. 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):476-9.
  4. 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):33-8.
  5. Rose E, DiClemente RJ, Wingood GM, et al. The validity of teens' and young adults' self-reported condom use. Arch Pediatr Adolesc Med. 2009;163(1):61-4.
  6. Gopolang FP. A comparison between self-reported condom use and presence of spermatozoa using TV in pouch and wet mount, among women enrolled in the Phase III Carraguard-clinical trial in Cape Town. (Abstract 520). Presented at Microbicides 2008, New Delhi, India, February 24-27, 2008.