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Discordance Between Spermatozoa Detection and Self-Reported Semen Exposure

Gallo, Maria F. PhD*; Sobel, Jack D. MD; Rompalo, Anne M. MD, ScM; Cu-Uvin, Susan MD§; Schoenbaum, Ellie MD; Jamieson, Denise J. MD, MPH*

doi: 10.1097/OLQ.0b013e318223be4b

An analysis of data from a prospective study of 1257 high-risk women revealed 7 predictors of discordance between self-reported lack of recent exposure to semen and detection of spermatozoa on Gram stain, suggesting that inaccuracies in the reporting of sexual behaviors cannot be assumed to be distributed randomly.

Analysis of 1257 high-risk women found several predictors of discordance between self reports and an objective marker of semen exposure, suggesting inaccuracies in reporting sexual behaviors are not randomly distributed.

From the *Division of Reproductive Health, Centers for Disease Control and Prevention, Atlanta, GA; †Department of Medicine, Wayne State University School of Medicine, Detroit, MI; ‡Division of Infectious Diseases, Johns Hopkins University School of Medicine, Baltimore, MD; §Obstetrics and Gynecology and Medicine, the Miriam Hospital, Brown University, Providence, RI; and ¶Einstein-Montefiore Institute for Clinical & Translational Research, Albert Einstein College of Medicine, Bronx, NY

The HIV Epidemiology Research Study Group consists of the following: Robert S. Klein, MD, Ellie Schoenbaum, MD, Julia Arnsten, MD, MPH, Robert D. Burk, MD, Chee Jen Chang, PhD, Penelope Demas, PhD, and Andrea Howard, MD, MSc, from Montefiore Medical Center and the Albert Einstein College of Medicine; Paula Schuman, MD, and Jack Sobel, MD, from the Wayne State University School of Medicine; Anne Rompalo, MD, David Vlahov, PhD, and David Celentano, PhD, from The Johns Hopkins University School of Medicine; Charles Carpenter, MD, and Kenneth Mayer, MD, from the Brown University School of Medicine; Ann Duerr, MD, Lytt I. Gardner, PhD, Scott Holmberg, MD, Denise Jamieson, MD, MPH, Jan Moore, PhD, Ruby Phelps, Dawn Smith, MD, and Dora Warren, PhD, from the Centers for Disease Control and Prevention; and Katherine Davenny, PhD, from the National Institute of Drug Abuse.

Supported by Centers for Disease Control and Prevention cooperative agreement numbers U64/CCU106795, U64/CCU206798, U64/CCU306802, and U64/CCU506831.

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, Division of Reproductive Health, Centers for Disease Control and Prevention, 4770 Buford Highway, Mail Stop K-34, Atlanta, GA 30341. E-mail:

Received for publication December 2, 2010, and accepted April 25, 2011.

Evaluations of behavioral interventions to prevent the transmission of human immunodeficiency virus (HIV)/sexually transmitted infections have largely relied on self-reported data.1–6 However, self-reported data on sexual behaviors could have poor validity for several reasons, namely, social desirability bias, recall bias, lack of awareness of exposure (e.g., undetected condom breakage), and poor comprehension or misinterpretations of the survey questions. Studies have found semen biomarkers in vaginal fluid specimens from women who reported either a lack of recent coitus or engaging only in recent coitus protected by a condom.7–12 Another study, also involving the detection of a semen biomarker in vaginal fluid, suggests that women's reports of condom problems could be unreliable.13

Historically, forensic science has employed Gram staining to detect spermatozoa in investigations of sexual assault cases.14 Spermatozoa have been detected by microscopic examination of vaginal fluid specimens for up to 10 days after exposure to semen, although they generally clear by 12 to 36 hours.15,16 More sensitive markers of semen, including prostate-specific antigen (PSA) and Y chromosome have since been developed.17–20 Identification of spermatozoa, though, is specific for semen exposure; it is unlikely to be a false-positive measure.14 Furthermore, the ability to detect spermatozoa and its clearance time are unlikely to differ with most participant characteristics and behaviors.

Using data from the HIV Epidemiology Research Study, we compared the detection of spermatozoa in women's reporting of lack of exposure to semen in order to identify predictors of discordance between the 2 measures of exposure. HIV Epidemiology Research Study, a prospective cohort study of HIV infection in women, enrolled 871 HIV-infected women and 439 HIV-uninfected women between 1993 and 1995 in 4 US sites.21 Participants had to be 16 to 55 years of age, without AIDS-defining clinical diagnosis, either be injection drug users or have high-risk sexual behaviors, and give informed consent for participation. Ethical review boards at the study sites and the Centers for Disease Control and Prevention approved the research. Participants were to complete follow-up visits at 6-month intervals after the enrollment visit. At all visits, participants were interviewed for demographical, health and behavioral information, and underwent a physical (including pelvic) examination.

Spermatozoa were detected morphologically during routine Gram stain evaluation of vaginal secretions for Nugent scoring to diagnose bacterial vaginosis.22 For Gram staining, swabs were obtained by direct scraping of vaginal walls in the middle third of the vagina and by sampling the pooled secretions visible in the lower blade of speculum. A single, certified technician read all of the slides. Trichomoniasis was diagnosed by wet mount microscopy, and vaginal cultures for Candida species were performed. Cervicovaginal lavage fluid was aliquoted and frozen for later testing by polymerase chain reaction for HPV.23

Discordance between participant reports and biologic evidence of exposure to semen was defined as reporting no unprotected sex in the past 6 months and yet having spermatozoa detected. We assessed both time-independent and time-dependent variables measured at baseline and follow-up visits, using logistic regression with generalized estimating equations to control for correlation between multiple study visits from individual women. For the multivariable analysis, we fit a full model with all potential predictors and then performed manual backward elimination of variables that were not associated on the basis of a P value of 0.05.24

We excluded 12 participants who seroconverted to HIV during the study and only included the first 10 visits from each participant. Additional visits were excluded for missing data on spermatozoa (N = 566; 5.9%) or self-reported semen exposure data (N = 36; 0.4%). Consequently, the analysis is based on 9008 study visits from 1257 women. Spermatozoa were detected in 9.3% (N = 841) of the visits and 461 women had at least one visit in which the spermatozoa were detected. Among the visits with spermatozoa identified, 29.3% and 5.0% were accompanied by reports of consistent condom use or no sexual activity, respectively (Table 1). Overall, 3.2% (288/9008) of the visits had discordant biomarker and self-reported data. About 16.3% (205/1257) of the women had discordant results at one or more visits. Among these women, most had discordant results at only one visit (N = 150), whereas the remainder had discordant results at 2 (N = 38), 3 (N = 12), 5 (N = 4), or 6 (N = 1) visits.



We found 7 predictors of discordance in the multivariable analysis between self-reported lack of self-reported exposure to semen within the past 6 months and an objective biologic measure of semen exposure (Table 2). First, frequency of discordance differed by study site which could have resulted from unmeasured differences in study populations between sites or from disparities in the ability of the interviewers between the sites to elicit accurate reports from participants. Young age was associated with more discordance, and black or Hispanic race/ethnicity women had about twice the odds of discordance compared to white race. These participant factors also could have influenced interviewers' ability to build the rapport necessary to obtain valid self-reported data. Positivity for HIV at baseline visit (aOR, 2.8; 95% CI, 1.7–4.6) and visits in which women were positive for bacterial vaginosis (aOR, 1.9; 95% CI, 1.5–2.5) or HIV (aOR, 1.3; 95% CI, 1.0–1.8) were also more likely to have discordant results than visits without these conditions. Finally, reporting current injection drug use was associated with less discordance. Although substance use during coitus could impair a participant's ability to recall behaviors accurately later, women who are willing to admit to injection drug use might also be more willing to report engaging in unprotected coitus than women who do not admit to be using drugs.





Study findings have unknown generalizability to other populations. Also, spermatozoa is not a sensitive measure of recent exposure to semen; for example, Culhane et al. found spermatozoa in only 36% of vaginal specimens that were positive for PSA.18 Furthermore, the recall period for the self-reported exposure in this study is much longer than the clearance time for spermatozoa. Thus, the identification of spermatozoa is inadequate for measuring the true frequency of either semen exposure or its discordance with participant reporting of exposure. On the other hand, the ability to detect spermatozoa and its clearance time is unlikely to differ by most participant attributes and behaviors. Consequently, spermatozoa detection is appropriate for assessing factors associated with discordant self reporting of semen exposure.

Prior research has called into question the validity of self-reported data related to sexual behaviors. Studies involving the detection of PSA7,8,10,11 or Y chromosome9,12 in vaginal fluid as evidence of recent exposure to a partner's semen suggest that self reports of unprotected coitus could be underestimations. A trial of the candidate microbicide PRO 2000 found that although 52% to 67% of participants reported consistent condom use in the past week, biologic evidence of unprotected coitus (i.e., pregnancy or acquisition of HIV/sexually transmitted infections) suggested that consistent condom use during the previous year was <25%.25 Similarly, a trial of the candidate microbicide, Carraguard, found substantial difference between the proportion of participants who reported gel use at last sex act (96%) and the proportion of gel applicators that, based on an objective staining assay, appeared to have been inserted vaginally (42%).26

Social desirability bias generally is assumed to be the main threat to the validity of participant reports of sexual behavior with efforts often directed toward improving the interview methodology as a means of reducing intentional misreporting.27 The validity of this assumption, though, has not been empirically demonstrated. If self reports instead are inaccurate because of faulty recall (e.g., from substance use or complicated or varying patterns of exposure) or unknown exposure (e.g., unawareness of partner's failure to put on a condom or undetected condom malfunctions), then efforts to improve the wording of questionnaires or the mode of administration may be unsuccessful. For example, a systematic review of studies comparing questionnaire delivery modes for collecting data on sexual behavior concluded that the use of audio computer-assisted survey instruments can reduce reporting bias.28 However, none of the trials included in the review used a biologic marker of semen exposure to assess the accuracy of the different modes of reporting under comparison. In contrast, the sole trial conducted to date that used a biologic marker of semen exposure to compare the validity of interview modes did not find a difference in the validity of self-reported data on semen exposure when collected with audio computer-assisted survey instruments versus face-to-face interviews.7

Employing a randomized study design to compare interventions would not necessarily circumvent potential problems with using self-reported data as a surrogate. For example, studies have been concluded on the efficacy of abstinence-only interventions29–31 and interventions to promote condom use32–34 based only on self-reported behavioral outcomes. However, bias in the participant reporting of abstinence or condom use could have been differential between study groups; women in the intervention arm could be expected to have more motivation to alter their responses as a result of social desirability bias or to please the interviewer. Interviewers might even contribute unconsciously to this difference between groups if they are cognizant of the study arm assignments and if they fail to remain completely neutral during data collection. Thus, differences in self-reported surrogate end points between study arms can be attributed to differential bias rather than the intervention under study.

In summary, we found several predictors of having discordant measures of recent semen exposure when assessed with both spermatozoa detected in Gram-stained vaginal specimens and participant reporting of coitus and condom use. Given the number and range of predictors identified, researchers should not assume that inaccuracies in the reporting of sexual behaviors are distributed randomly across a study population. Future research should include biologic markers of exposure whenever feasible rather than rely exclusively on self reports of semen exposure for the evaluation of HIV/STI interventions.

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