Unprotected Anal Intercourse, Risk Reduction Behaviours, and Subsequent HIV Infection in a Cohort of Homosexual Men

Fengyi Jin; June Crawford; Garrett P Prestage; Iryna Zablotska; John Imrie; Susan C Kippax; John M Kaldor; Andrew E Grulich

Disclosures

AIDS. 2009;23(2):243-252. 

In This Article

Methods

Participants were recruited from a wide range of community-based settings in Sydney between June 2001 and December 2004, as described in detail elsewhere.[21] Men were eligible if they met the following criteria: reported having sex with other men within the previous 5 years; lived in Sydney or participated regularly in its gay community; and tested HIV negative at baseline. Signed informed consent was obtained. Participants were followed to the end of June 2007. Ethics approval was granted by the Ethics Committee at the University of New South Wales.

All eligible men willing to participate underwent annual face-to-face interviews, with 6-monthly telephone interviews between these visits. At each interview, detailed quantitative data on the number of episodes of UAI in the 6 months prior were collected. Participants reported the number of episodes of UAI separately for regular and for casual partners (defined by the participants), for the insertive and receptive positions, by HIV status of these partners (negative, positive or unknown). In addition, for UAI-R, they reported episodes separately by whether or not ejaculation occurred inside their rectum.

Methods of ascertainment of HIV seroconversion and estimation of the date of HIV infection have been described in detail elsewhere.[22] Briefly, incident HIV infections were identified through two sources. First, HIV diagnoses at the annual study visit were identified (n = 31). Second, identifiers were matched against the national HIV register to identify infections in people who tested outside the study (n = 22). The final match and the final study interviews occurred in June 2007.

In 36 HIV seroconverters who had no data on seroconversion symptoms, the midpoint between the last negative and first positive HIV tests was used to estimate the date of infection. Data on the completeness of the western blot and the occurrence of seroconversion symptoms were available from another study in 17 HIV seroconverters.[23,24] In these participants, if the western blot was incomplete, the later of the midpoint or 2 weeks prior to symptom onset was used as the estimated infection date (n = 9). If the western blot was complete, the earlier of the two was used (n = 8).

Risk reduction behaviours were derived from participants' reports about modes of UAI. With the exception of negotiated safety, intent to engage in such behaviours was not assessed. The terms 'serosorting', 'negotiated safety' and 'strategic positioning' were not used in the study questionnaire.

Serosorting. Serosorting between interviews was defined as reporting UAI in that period and reporting that all this UAI was with partners who were reported by study participants to be HIV negative. This was regardless of whether the UAI was with regular or casual partners, or was insertive or receptive. Negotiated safety was defined as a form of serosorting with regular partners in which the following seven criteria were met, as previously defined in Australian community-based research:[15,16] they identified a primary regular partner; the relationship was of more than 6 months duration; the result of the primary regular partner's last HIV test was HIV negative; there was a clear spoken agreement that UAI was allowed within the relationship; there was a clear spoken agreement that there was to be no UAI outside the relationship; the participant and his partner had mutually disclosed their most recent HIV test result; and UAI was reported exclusively with the primary regular partner.

Strategic Positioning (Insertive Only Unprotected Anal Intercourse). Strategic positioning was defined as reporting UAI in a study period and reporting that all this UAI was insertive. This was regardless of whether the UAI was with regular or casual partners and the HIV status of partners.

Withdrawal. Withdrawal was defined as reporting UAI-R in a study period, and that none of the UAI-R had involved ejaculation inside the rectum. This was regardless of whether UAI-R was with regular or casual partners, and the HIV status of partners.

Statistical analyses were performed using STATA 10.0 (STATA Corporation, College Station, Texas, USA). The HIV incidence was calculated as the number of seroconversions divided by the person-years followed. Total person-years were calculated from study entry to the time of HIV infection, to the last study interview, or to the end of June 2007 for those who remained HIV negative. The exact binomial method was used to calculate 95% confidence intervals (CIs).

In 13 participants whose seroconversions were identified through matching, the estimated date of infection was later than their last interview due to loss to follow-up. In these individuals, there were no behavioural data available at the time of estimated infection. Information obtained from the last interview was carried forward for risk factor analysis in seven participants in whom the estimated date of infection was less than 12 months after the last interview. Six participants whose estimated dates of infection were more than 12 months later were excluded from risk factor analysis.

Univariate and multivariate Cox regression models were developed to examine the number of episodes of different modes of UAI as risk factors and hazard ratios were calculated. The association between UAI and HIV seroconversion was examined according to three categories of sexual position (insertive, receptive with withdrawal and receptive with ejaculation), three categories of partner type (regular, casual, and combined regular and casual), and three categories of partners' reported HIV status (negative, positive and unknown). This led to the creation of 27 separate risk behaviours (e.g. insertive UAI with HIV-negative regular partners). In each of these analyses, we examined the effect of number of episodes of that type of UAI in the last 6 months, grouped as 0, one to five, and more than five episodes. Modes of UAI with regular and casual partners combined that were significantly related with HIV infection were entered into a multivariate model using forward stepwise regression.

For risk reduction behaviours, mutually exclusive categories were created for serosorting, strategic positioning and withdrawal. Negotiated safety was examined as a type of serosorting for those who reported a regular partner. Associations between reporting serosorting and each of the other risk reduction behaviours on each study visit occasion were examined using logistic regression, after adjustment for interparticipant correlation,[25] and graphically displayed using pie diagrams. To assess confounding between behaviours, stratified analyses of HIV risk were performed among men who reported UAI with HIV-positive partners, and among those who reported UAI only with HIV-negative partners.

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