To determine whether the process of informing research participants that they would be tested for the presence of a biological marker of semen exposure would reduce bias in their reports of unprotected sex

Gallo, M. F

Hawken, M.

Hobbs, M. M

Janowitz, B.

Ombidi, W.

Omungo, Z.

Thomsen, S. C

Tucker, H.

Wong, E. L

Carolina Digital Repository

IN PRACTICERandomised controlled trial on whether advance knowledgeof prostate-specific antigen testing improves participantreporting of unprotected sexSarah C Thomsen, Maria F Gallo, Wilkister Ombidi, Zablon Omungo, Barbara Janowitz, MarkHawken, Heidi Tucker, Emelita L Wong, Marcia M Hobbs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Sex Transm Infect 2007;83:419–420. doi: 10.1136/sti.2006.022772Objectives: To determine whether the process of informingresearch participants that they would be tested for the presenceof a biological marker of semen exposure would reduce bias intheir reports of unprotected sex.Methods: A randomised trial of 210 female sex workers fromMombasa, Kenya, was conducted, where half the group hadadvance knowledge (via the request for informed consent) thatthey would be tested for prostate-specific antigen (PSA) in theirvaginal fluid before they reported on sex and condom use forthe past 48 h. The other half were invited to participate (viaadditional informed consent) in the test for PSA after they hadalready consented to be questioned and reported on thesesexual behaviours. A trained nurse instructed participants toself-swab to collect vaginal fluid specimens, which were testedfor PSA using ELISA.Results: Reporting of unprotected sex did not differ betweenthose with advance knowledge of the test for PSA and thosewithout this knowledge (14.3% v 11.4%, respectively; p = 0.27).Surprisingly, more women with advance knowledge (15.8%)had discrepant self reports and PSA results than women withoutadvance knowledge (9.1%); however, the difference was notstatistically significant (OR 1.9; 95% CI 0.8 to 4.5).Conclusions: Knowing that one’s answers to a questionnairecould be verified with a biological marker of semen exposuredid not make respondents more likely to report unprotected sex.Evaluations of behavioural interventions designed to pre-vent transmission of HIV/sexually transmitted infectionsfrequently rely on self-reported condom use data tomeasure success, yet such data are often acknowledged to bepotentially inaccurate, either owing to faulty recall or socialdesirability bias.1 2 Although research techniques to improve thevalidity of self-reported data on sexual behaviour have beenrecommended,3 their ability to reduce information bias has notbeen shown. Until recently, the objective assessment ofresearch methods designed to improve the validity of self-reports of sex and condom use has not been possible. However,verifying recent unprotected sex is now feasible by testingwomen for prostate-specific antigen (PSA), a protein found inhigh concentrations in semen and detectable in vaginalsecretions from women up to 48 h after unprotected sex.4–8We conducted a randomised controlled trial to determinewhether the process of informing participants about PSAtesting would reduce reporting bias. We compared womenwho knew that their vaginal specimens were to be tested forPSA before they completed the questionnaire on sex andcondom use with women who did not have this knowledge inadvance. We hypothesised that those with advance knowledgeof the PSA testing would report more unprotected sex andwould have better agreement between the PSA test results andtheir self-reported data than those without advance testknowledge.METHODSThe population consisted of 210 female sex workers associatedwith a peer education programme designed to reduce transmis-sion of HIV/sexually transmitted infections in Mombasa,Kenya. The trial took place during the baseline measurementof a larger study examining the effects of introducing thefemale condom in a peer education programme with sexworkers.9 The institutional review boards of the sponsoringinstitution and Kenyatta National Hospital, Nairobi, Kenya,approved the study.Sex workers who fulfilled the eligibility criteria wererandomised into two groups of equal sizes using a previouslycreated randomisation list. Both the randomisation process andthe group assignments were unblinded. The first groupprovided written informed consent for both the questionnaireand the PSA test before we administered the sex and condomuse questionnaire and took vaginal specimens for PSA testing.By contrast, the second group was first asked for informedconsent for the questionnaire and were told that they would beasked to participate in a second study only after they hadcompleted the questionnaire. At that point, we requestedinformed consent for the PSA test. The informed consent forthe PSA testing advised participants that if they had sexwithout a male or female condom or if they used the condomincorrectly, semen could be detected for 1–2 days afterwards.Although we informed participants that we would test for this,we did not assess the participants’ comprehension of the studyprocedures or objectives. For both groups, a trained nurse usedpictures to instruct participants on sample collection and thenleft the women to self-swab in private. Specimens were airdried and sent by air to a laboratory in the US for analysis. Weidentified PSA using a microparticle enzyme immunoassay(IMx, Abbott Laboratories, Abbott Park, Illinois, USA).We examined two hypotheses: (1) whether the group withadvance knowledge of the PSA test would report moreunprotected sex for the past 48 h than the group withoutadvance knowledge and (2) whether the group with advanceknowledge would have less disagreement between their PSAresults and self-reports of unprotected sex. We measured onlyone type of disagreement: reporting no sex or protected sex forthe past 48 h, yet testing positive for PSA. We did not assessdisagreement resulting from reporting exposure yet testingnegative for PSA because other factors could explain theabsence of PSA, such as the effect of practices such as douchingAbbreviations: PSA, prostate-specific antigen419www.stijournal.comor the marker’s short clearance time. Although PSA can bedetected with high sensitivity (98–100%) immediately aftersemen exposure, the antigen clears rapidly from the vagina.4 5Macaluso et al4 found PSA in only 29% of specimens collectedfrom women 24 h after clinical insemination with 1 ml of theirpartner’s semen and in 3% of specimens at 48 h. We tested thehypotheses with one-sided x2 tests.RESULTSAll of the 210 eligible women who were recruited to the studyagreed to participate. Two participants in the group without theadvance knowledge of PSA testing declined to self-swab atbaseline; however, both contributed a swab for PSA testing atthe follow-up visit. Owing to missing test results, we have PSAdata for 194 participants.We found no difference between the advance knowledge(n = 105) and no advance knowledge groups (n = 105) in theproportion of women who reported exposure to unprotected sexfor the past 48 h (14.3% and 11.4%, respectively; p = 0.27). Agreater proportion of those who knew about the PSA test inadvance (15.8%; n = 15) reported no exposure for the past 48 hand yet tested positive for PSA than those without the advanceknowledge (9.1%; n = 9). However, the odds of having this typeof discordant self-reported and PSA data did not differ byrandomisation group (p = 0.08; OR 1.9; 95% CI 0.8 to 4.5).DISCUSSIONWomen who knew about the PSA test in advance did not reportmore exposure than those without advance knowledge.Surprisingly, more women with the advance test knowledgehad discordant self-report and PSA results than the comparisongroup; however, this difference was not statistically significant.Whether respondents who know that their responses can beverified would be less likely to misrepresent their sex andcondom use to researchers is unknown. However, these resultsdo not support the assumption that such information necessa-rily would motivate individuals to provide more accurateresponses. Other psychosocial and cultural factors—besidesthe desire to present oneself in a positive light—could motivatea person to respond inaccurately. For example, participantscould become confused while answering questionnaires aboutwhat they are ‘‘supposed to do’’,10 or they could lie on purposeto ‘‘test’’ the system. Owing to the small sample size, werecommend that similar studies using PSA be conducted todetermine the directionality of the effects (if any) on accuracyof self-report of sex and condom use derived from usingresearch methods (eg, advance knowledge of biological testingor audio computer-assisted self-interviewing) that are believedto reduce social desirability bias.ACKNOWLEDGEMENTSWe thank Jane Parker and Kimberly Rich for performing the assays forPSA. This study was funded by the United States Agency forInternational Development (cooperative agreement #AID/CCP-3079-A-00-5022-00) and supported by the Microbiology Core Laboratory ofthe North Carolina Sexually Transmitted Infections and TopicalMicrobicide Cooperative Research Center (NIH grant #U19-AI031496). The views expressed in this document, however, do notnecessarily reflect those of the funding agencies.Authors’ affiliations. . . . . . . . . . . . . . . . . . . . . . .Sarah C Thomsen, Maria F Gallo, Barbara Janowitz, Heidi Tucker,Emelita L Wong, Family Health International, Research Triangle Park,North Carolina, USAWilkister Ombidi, Mark Hawken, International Centre for ReproductiveHealth, Mombasa, KenyaZablon Omungo, Family Health International, Nairobi, KenyaMarcia M Hobbs, University of North Carolina at Chapel Hill, Chapel Hill,North Carolina, USACompeting interests: None.Contributors: The idea for the study came from BJ, who also reviewedanalyses and the text. SCT designed and oversaw the conduct of the studyand, along with, MFG, who coordinated the PSA portion of the study,wrote the bulk of the text. MH was the principal investigator and WO wasthe research coordinator. ZO conducted training and monitored the study.ELW designed and approved all statistical analyses, which were carried outby HT. MMH oversaw all laboratory procedures. All authors contributed tothe writing of the manuscript and have reviewed and approved its content.Correspondence to: Dr M F Gallo, Centers for Disease Control andPrevention, Division of Reproductive Health, 4770 Buford Highway, NE,MS K-34, Atlanta, GA 30341, USA; mgallo@cdc.govAccepted 16 November 2006Published Online First 29 November 2006REFERENCES1 Catania JA, Gibson DR, Chitwood DD, et al. Methodological problems in AIDSbehavioral research: influences on measurement error and participation bias instudies of sexual behavior. Psychol Bull 1990;108:339–62.2 Zenilman JM, Weisman CS, Rompalo AM, et al. Condom use to prevent incidentSTDs: the validity of self-reported condom use. Sex Transm Dis 1995;22:15–21.3 Pequegnat W, Fishbein M, Celentano D, et al. NIMH/APPC workgroup onbehavioural and biological outcomes in HIV/STD prevention studies: a positionstatement. Sex Transm Dis 2000;27:127–32.4 Macaluso M, Lawson L, Akers R, et al. Prostate-specific antigen in vaginal fluid asa biologic marker of condom failure. Contraception 1999;59:195–201.5 Lawson ML, Maculuso M, Bloom A, et al. Objective markers of condom failure.Sex Transm Dis 1998;25:427–32.6 Steiner MJ, Feldblum, PJ, Padian, N. Invited commentary: condomeffectiveness—will prostate-specific antigen shed new light on this perplexingproblem? Am J Epidemiol 2003;157:298–300.7 Gallo MF, Behets FM, Steiner MJ, et al. Prostate-specific antigen to ascertainreliability of self-reported coital exposure to semen. Sex Transm Dis2006;33:476–9.8 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,2006. In press.9 Thomsen SC, Ombidi W, Toroitich-Ruto C, et al. A prospective study as sessingthe effects of introducing the female condom in a sex worker population inMombasa, Kenya. Sex Transm Infect 2006;82:397–402.10 Arkin RM. Self-presentational styles. In: JT Tedeschi, eds. Impressionmanagement theory and social psychological research. San Diego, CA:Academic, 1981.Key MessagesN Women who knew that their questionnaire answers couldbe verified with a biological marker of semen exposurewere not more likely to report unprotected sex or havebetter agreement between self-reports and prostate-specific antigen (PSA) test results than women withoutthis advance knowledge.N Future studies should use PSA to evaluate the effect ofresearch methods designed to improve the accuracy ofself-reported sex and condom use data.420 Thomsen, Gallo, Ombidi, et alwww.stijournal.com

Randomised controlled trial on whether advance knowledge of prostate-specific antigen testing improves participant reporting of unprotected sex

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Randomised controlled trial on whether advance knowledge of prostate-specific antigen testing improves participant reporting of unprotected sex

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