Incident risk factors as predictors of HIV seroconversion in the Lisbon cohort of men who have sex with men: first results,

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1 Reserch rticles Incident risk fctors s predictors of HIV seroconversion in the Lisbon cohort of men who hve sex with men: first results, P Meireles (pul.meireles@ispup.up.pt) 1, R Lucs 1,2, C Crvlho 1,2, R Fuertes 3, J Brito 3, M J Cmpos 3, L Mendão 3, H Brros 1,3 1. EPIUnit, Institute of Public Helth, University of Porto, Porto, Portugl 2. Deprtment of Clinicl Epidemiology, Predictive Medicine nd Public Helth, University of Porto Medicl School, Porto, Portugl 3. Grupo Português de Activists sobre Trtmentos VIH/SIDA (GAT), Lisbo, Portugl Cittion style for this rticle: Meireles P, Lucs R, Crvlho C, Fuertes R, Brito J, Cmpos MJ, Mendão L, Brros H. Incident risk fctors s predictors of HIV seroconversion in the Lisbon cohort of men who hve sex with men: first results, Euro Surveill. 2015;20(14):pii= Avilble online: spx?articleid=21091 Article submitted on 31 August 2014 / published on 09 April 2015 HIV incidence in men who hve sex with men (MSM) is incresing in western countries, including Portugl. We imed to estimte HIV incidence nd to ssess how individul short-term chnges in exposures over time predict seroconversion. We evluted prticipnts of n open cohort of HIV-negtive MSM enrolled fter testing t community-bsed voluntry HIV counselling nd testing centre in Lisbon. At ech evlution structured questionnire ws completed nd HIV sttus ws scertined using rpid followed by confirmtory testing. Between April 2011 nd Februry 2014, 804 MSM were followed for totl of 893 person-yers. Predictors of HIV seroconversion were identified using Poisson generlised liner regression. The overll seroincidence ws 2.80/100 personyers (95% confidence intervl: ). Men who seroconverted hd higher men number of tests per yer. Seroconversions were significntly ssocited with prtner disclosure of HIV sttus during followup, newly-dopted unprotected nl intercourse (UAI) with stedy prtner nd being newly-dignosed with syphilis during follow-up. Likewise, sexul intercourse with HIV-positive men, hving n HIV-positive stedy prtner t lest once during follow-up nd persistent UAI with occsionl prtners were predictors of seroconversion. High HIV incidence in this cohort is likely driven by short-term contextul nd behviourl chnges during follow-up. Introduction A well-estblished body of potentil strtegies for the primry prevention of HIV infection stems from incresed understnding of disese pthogenesis nd trnsmission [1,2]. Still, there is evidence of growing HIV incidence mong men who hve sex with men (MSM) in western Europe, North Americ nd Austrli [3-8]. These trends re unlikely to be explined by chnges in surveillnce or testing prctices [3], rther reflecting the fct tht MSM remin t higher risk in most countries. This is pprent in the burden of newly-dignosed infections in the Europen Union nd Europen Economic Are: the lrgest frction of HIV dignoses reported in 2013 ws ttributble to sex between men (41.9%), followed by heterosexul trnsmission (32.4%), nd finlly by unsfe injection prctices (5.0%) [9]. This is lso the Portuguese pttern: fter severl yers of n HIV epidemic driven by unsfe drug injection, sex between men hs gined specil relevnce s trnsmission mode mking up 30.3% of ll reported cses in 2013 [10]. Two pioneering cross-sectionl studies [11,12] trgeting MSM living in Portugl collected extensive self-reported informtion, leding to the first lrming estimtes of the point prevlence of infection: 10.9% [13] nd 10.3% (personl communiction, A Gm, 2013). Monitoring defined cohorts of MSM provides timely estimtes of HIV incidence nd predictors beyond the limited informtion produced by cse reporting or cross-sectionl surveys. In previous prospective cohorts, the occurrence of new infections hs been modelled both s function of fctors tht directly increse infection risk (frequency of unprotected nl intercourse (UAI), virl lod of the index prtner, presence of sexully trnsmitted infections (STI)), s well s potentil mrkers of exposure, such s number of sex prtners, substnce use, nd dverse childhood circumstnces [14 19]. However, how individul exposures chnge over time nd how those chnges cn predict HIV seroconversion remins to be clrified. Innovtive community-bsed HIV testing nd counselling pproches hve been developed tht trget specific popultion groups t higher risk nd involve 1

2 community stkeholders s peer-counsellor nd key informnts [20]. As such, these re privileged settings for prospective reserch on the incidence nd drivers of the HIV epidemic mong MSM, with the ultimte gol of informing relistic preventive strtegies. The objectives of the present study were to estimte the incidence of HIV infection in cohort of MSM nd to ssess how individul short-term chnges in exposures predict seroconversion. Methods Cohort recruitment nd follow-up The Lisbon MSM cohort, estblished in April 2011, is n observtionl prospective study conducted t community-bsed voluntry HIV counselling nd testing centre in Lisbon, Portugl (CheckpointLX). It ws designed s n open cohort, nd inclusion criteri were: presenting for HIV testing t CheckpointLX, being mn ged 18 or more, reporting hving sex with other men nd hving negtive HIV test result t recruitment. All eligible individuls were invited to enter the cohort by CheckpointLX peer counsellors t their first visit. Follow-up ssessments were scheduled t intended intervls of 6 months, lthough the exct time between visits ws djusted ccording to the convenience of prticipnts. Since follow-up visits occurred whenever clients decided to pper for testing, this does not strictly constitute n intervl cohort nd it is likely tht smll proportion of MSM hd very short or long periods between visits: e.g. in our smple, 6.3% of men hd follow-ups shorter thn three months. This is problemtic for MSM who seroconvert between tests which re close in time (due to possible window period), which is why we opted to exclude five prticipnts with seroconversions tht occurred during follow-up periods of less thn three months. At ech visit structured questionnire ws dministered nd rpid HIV test ws performed by trined CheckpointLX peer counsellor. All prticipnts gve their written informed consent nd the study protocol ws pproved by the ethics committee of Hospitl de São João nd Medicl School, University of Porto (ID 104/12). Prticiption nd losses to follow-up Dt reported in this study refer to the period from April 2011 to Februry 2014, during which 3,301 potentil eligible individuls presented for testing, 195 (5.9%) of whom hd n HIV-rective test t entry nd therefore were not included in the cohort. The remining 3,106 (94.1%) were eligible to the cohort. Among those, 2,183 (70.3%) were enrolled, of whom 804 (36.8%) hd t lest one follow-up evlution ( person-yers of observtion) nd 923 (29.7%) choose not to prticipte. Those who choose not to prticipte were less self-identified s homosexul, less frequently born in Portugl, nd less educted thn those who chose to prticipte, but hd similr proportion of HIV testing before cohort entry. Opertionlly, prticipnts were clssified s lost to follow-up if they hd chosen to prticipte but ppered for testing only once (n=707). However, MSM who hd been recruited for the cohort recently (12 months or less before the end of the period considered in the present nlysis, i.e. from Februry 2013 to Februry 2014) were not considered lost to follow-up (n=672). Therefore, we ssumed n overll ttrition rte of 52%. MSM who were not followed-up were older thn those who were (31.2 vs 30.3 yers old, p=0.034), but both groups were similr regrding the remining bckground chrcteristics. Also, no significnt differences were found between MSM who ppered for followup nd those who did not regrding such behviourl chrcteristics s: sexul intercourse with HIV positive men (13.5% vs 12.9%, p = 0.955), hving n HIV-positive stedy prtner (5.8% vs 5.2%, p = 0.528), nd condom use with stedy prtner (27.7% vs 27.9%, p > 0.999) nd with n occsionl prtner in the previous 12 months (57.1% vs 51.7%, p = 0.069). Rpid HIV testing Rpid HIV-1 nd HIV-2 testing ws performed t ech visit. From April 2011 to April 2012 two commercil kits were used, the Retrocheck HIV (QUALPRO DIAGNOSTICS, Go, Indi) (mnufcturer-described sensitivity = % nd specificity = 99.75%) nd Hexgon HIV (Humn GmbH, Wiesbden, Germny) (sensitivity = % nd specificity = 99.50%) nd since tht time, only the Alere Determine HIV-1/2 (Alere Medicl Co., Ltd. Chib, Jpn) (sensitivity = % nd specificity = 99.75%) hs been used. In cse of rective test, n outptient ppointment ws scheduled t Snto António dos Cpuchos Hospitl s HIV/ Infectious diseses clinic in Lisbon where confirmtory test ws performed. Pre- nd post-test counselling ws offered t ech visit. Study instruments nd vribles Structured questionnires were dministered t entry nd t ech follow-up visit collecting dt on bckground nd behviourl chrcteristics, ccording to Europen Centre for Disese Prevention nd Control (ECDC) [21] nd the Joint United Ntions Progrmme on HIV/AIDS (UNAIDS) guidelines [22] for HIV surveillnce. For time-vrying informtion the recll period ws the previous 12 months (cohort entry questionnire) or the time since the previous ssessment (follow-up visits). Bckground chrcteristics included ge, sex, country of birth, eductionl level nd sexul identity. Behviourl indictors included informtion on the following topics: History of previous HIV testing nd resons for index test; Age t first nl intercourse, role t nl intercourse, chrcteristics of sexul prtners (bisexul 2

3 men, men with different sexul prtners, sex workers, HIV-positive men, people who inject drugs, women nd trios/group sex), stedy (number, sex nd HIV sttus) nd occsionl prtners, hving been pid for sex nd venues used to meet occsionl prtners; Frequency of condom use for nl intercourse with stedy nd occsionl prtners. Use of lcohol or recretionl drugs (cnnbis, lysergic cid diethylmide (LSD), poppers, heroin, ecstsy, mphetmines, mephedrone, gmmhydroxybutyric cid (GHB), ketmine nd cocine) before or during intercourse; Knowledge nd use of non-occuptionl postexposure prophylxis for HIV; History of other STI nd heptitis. We were interested in ssessing whether intrindividul chnges over time in well-documented determinnts of HIV incidence were predictive of seroconversion. Even though multiple chnges in those determinnts throughout follow-up were theoreticlly possible, we opted to use informtion collected t two time points for ech prticipnt: cohort entry nd either the visit of the first HIV positive test (for MSM who seroconverted) or the most recent visit (for the remining MSM). This choice ws bsed on two min rguments: i) the mjority (53.8%) of prticipnts hd only two visits, nd ii) for prticipnts with three or more visits, using multiple combintions of informtion from ll visits did not chnge the direction of ssocitions or the min conclusions, i.e. first nd lst visit were good surrogtes for exposure chnges during follow-up (dt not shown). For this purpose we creted new vribles for time-vrying informtion tht compiled responses from the first nd the most recent visit, ctegorised s Yes to No or No to Yes if the informtion hd chnged between those visits, nd No nd No or Yes nd Yes if nswers were persistent. In cse of 24 prticipnts with more thn two visits who preferred not to disclose one or more of the behviourl items t the most recent visit, we used the informtion obtined in the preceding visit. This option did not lter substntilly the mgnitude of ssocitions. Sttisticl nlysis Chrcteristics of prticipnts t cohort entry were described using bsolute frequencies nd proportions in the cse of ctegoricl vribles. Mens nd stndrd devition (SD) or medin nd percentiles 25 nd 75 (P25-P75) were used, s pproprite, to describe continuous vribles. In dt nlysis, the missing ctegory ws excluded from the denomintor for ech item. In time-vrying informtion relted to chrcteristics of sexul prtners, the options I do not know nd the No options were collpsed once the incidence rtes in both groups were similr. Unprotected nl intercourse (UAI) ws defined s not lwys hving used condom in receptive or insertive nl sex. Incidence rtes with 95% confidence intervls (95% CI) were estimted with time t risk defined s the period between recruitment nd the most recent follow-up visit. In MSM who seroconverted, hlf of the period between the lst HIV-negtive test nd the first HIV-positive test ws subtrcted. Tble 1A Chrcteristics t entry of prticipnts followed in the cohort of men who hve sex with men, Lisbon, Portugl, (n=804) Prticipnts followed-up 804 Bckground chrcteristics Age (yers), men (SD) 30.3 (8.9) Missing 0 Sexul identity, n (%) Homosexul 692 (86.1) Bisexul/heterosexul/other 109 (13.6) Prefer not to nswer 3 (0.4) Missing 0 Country of origin, n (%) Portugl 575 (75.0) Other country 190 (24.7) Prefer not to nswer 2 (0.3) Missing 37 Eductionl level (schooling yers), n (%) Less thn higher eduction ( 12 yers of school) 317 (39.5) Higher eduction (> 12 yers of school) 483 (60.1) Other/Prefer not to nswer 3 (0.3) Missing 1 HIV testing Previous HIV testing, n (%) No 115 (15.2) Yes 636 (84.1) Did not know 5 (0.7) Missing 48 Number of previous tests, medin (P25-P75) 4 (2 7) Missing 16 Resons for index test, n (%) To check helth sttus/routine 602 (77.9) Perception of HIV exposure more thn 3 months before 426 (54.0) Perception of HIV exposure in the previous 3 months 357 (44.8) Accident with condom use (rupture/left inside) 65 (8.4) Prtner dignosed HIV+ /Disclosed HIV+ sttus 59 (7.6) Possible window period by the time of the lst test 55 (7.2) To stop using condom with my prtner 38 (5.0) My prtner sked me to test for HIV 34 (4.4) Symptoms / Medicl indiction 20 (2.6) Among prticipnts who hd hd previous HIV test (n=636). b Among prticipnts who hd stedy prtner in the previous 12 months (n=501). c Among prticipnts who hd n occsionl prtner in the previous 12 months (n=713). d Among prticipnts who hd n HIV-positive stedy prtner (n=46). 3

4 Tble 1B Chrcteristics t entry of prticipnts followed in the cohort of men who hve sex with men, Lisbon, Portugl, (n=804) Prticipnts followed-up 804 Sexul life nd prtners Age t first nl intercourse, medin (P25-P75) 18.0 ( ) Missing 37 Role in nl intercourse, n (%) Only insertive 192 (24.1) Only receptive 72 (9.0) Verstile 525 (66.0) Prefer not to nswer 7 (0.9) Missing 8 Sex with t lest one of the following in the previous 12 months, n (%) Bisexul men No 420 (53.1) Yes 271 (34.3) Did not know 98 (12.4) Prefer not to nswer 2 (0.2) Missing 13 Men with different sex prtners No 148 (18.7) Yes 588 (74.2) Did not know 54 (6.8) Prefer not to nswer 2 (0.3) Missing 12 Sex workers (even if not pid) No 707 (89.4) Yes 51 (6.4) Did not know 31 (3.9) Prefer not to nswer 2 (0.3) Missing 13 HIV-positive men No 401 (50.7) Yes 107 (13.5) Did not know 281 (35.5) Prefer not to nswer 2 (0.3) Missing 13 People who inject drugs No 719 (90.9) Yes 4 (0.5) Did not know 65 (8.2) Prefer not to nswer 3 (0.4) Missing 13 Women No 690 (87.2) Yes 99 (12.5) Did not know 0 Prefer not to nswer 2 (0.3) Missing 13 Trios/group sex No 563 (71.2) Yes 224 (28.3) Prticipnts followed-up 804 Sexul life nd prtners Did not know 1 (0.1) Prefer not to nswer 3 (0.4) Missing 13 Stedy prtner in the previous 12 months, n (%) No 301 (37.4) One stedy prtner 449 (55.8) More thn one stedy prtner 52 (6.5) Prefer not to nswer 2 (0.2) Missing 0 HIV sttus of stedy prtner b, n (%) HIV negtive 310 (62.5) HIV positive 46 (9.3) Did not know 139 (28.0) Prefer not to nswer 1 (0.2) Missing 5 Occsionl prtners in the previous 12 months, n (%) No 89 (11.1) Yes 713 (88.7) Prefer not to nswer 2 (0.2) Missing 0 Number of occsionl prtners in the previous 12 months c, medin (P25-P75) 5 (2 10) Missing 19 Hving sex for money or drugs in the previous 12 months c, n (%) No 693 (97.3) Yes 19 (2.7) Missing 1 Venues used to meet occsionl prtners c, n (%) Internet 522 (73.9) Other venues (discos/gy brs, gym, outdoor cruising venues) 458 (57.6) Only sexul venues (suns, drk room, sex clubs) 166 (20.9) Among prticipnts who hd hd previous HIV test (n=636). b Among prticipnts who hd stedy prtner in the previous 12 months (n=501). c Among prticipnts who hd n occsionl prtner in the previous 12 months (n=713). d Among prticipnts who hd n HIV-positive stedy prtner (n=46). 4

5 Tble 1C Chrcteristics t entry of prticipnts followed in the cohort of men who hve sex with men, Lisbon, Portugl, (n=804) Prticipnts followed-up 804 Unprotected nl intercourse (UAI), n (%) UAI with stedy prtner in the previous 12 months b No 130 (27.4) Yes 344 (72.4) Prefer not to nswer 1 (0.2) Missing 26 UAI in the previous 12 months with n HIV-positive stedy prtner d No 26 (59.1) Yes 18 (40.9) Missing 2 UAI with occsionl prtners in the previous 12 months c No 375 (56.1) Yes 292 (43.7) Prefer not to nswer 1 (0.1) Missing 45 Recretionl drugs, n (%) Used recretionl drugs before or during sexul intercourse in the previous 12 months Never 552 (69.9) Alwys/often/occsionlly/rrely 238 (30.1) Missing 14 Post-exposure prophylxis (PEP), n (%) Does not know bout PEP 411 (54.7) Knows but never used 317 (42.2) Knows nd used 23 (3.1) Missing 53 Sexully trnsmitted infections, n (%) In the previous 12 months: Gonorrhe 20 (2.5) Syphilis 13 (1.6) Condylom or genitl wrts 10 (1.3) Chlmydi 7 (0.9) Genitl herpes 1 (0.1) Trichomons 1 (0.1) History of heptitis, n (%) Heptitis B 18 (2.3) Heptitis C 3 (0.4) Among prticipnts who hd hd previous HIV test (n=636). b Among prticipnts who hd stedy prtner in the previous 12 months (n=501). c Among prticipnts who hd n occsionl prtner in the previous 12 months (n=713). d Among prticipnts who hd n HIV-positive stedy prtner (n=46). Poisson generlised liner regression ws used to identify predictors of HIV seroconversion with the defult log link nd offset in the vrible follow-up time (t). To mesure the mgnitude of ssocitions, crude nd djusted incidence rte rtios (IRR nd IRR) nd respective 95% CI were computed. Vribles whose regression coefficient through the Wld test hd p < 0.10 in the univrite nlyses were further djusted for UAI with stedy prtner nd UAI with occsionl prtners to estimte their direct effects, even though we cknowledge tht UAI my be n intermedite step in the cusl mechnism. For the multivrite nlysis, significnce level ws set t p < All sttisticl nlyses were computed with Sttisticl Pckge for Socil Sciences (SPSS) for Windows, version 22.0 (SPSS Inc., Chicgo, Illinois, US). Results Chrcteristics of prticipnts t cohort entry Bckground nd behviourl chrcteristics t entry for the 804 prticipnts who cme for follow-up visit between April 2011 nd Februry 2014 re summrised in Tble 1. Briefly, men (SD) ge ws 30.3 (8.9) yers; 86.1% (692/804) of MSM self-identified s homosexul; 75.0% (575/767) were born in Portugl nd 60.1% (483/803) hd over 12 yers of schooling. HIV testing before cohort entry ws reported by 84.1% (636/756) of prticipnts. Slightly less thn two thirds (501/804) of prticipnts hd t lest one stedy prtner, of whom 9.3% (46/496) were in serodiscordnt couple. UAI with stedy prtner in the yer before cohort entry ws reported by 72.4% (344/475); in prticulr, 40.9% (18/44) of MSM who hd n HIV-positive prtner hd UAI in the sme period; UAI with one or more occsionl prtners ws reported by 43.7% (292/668) in the sme period. Almost one third (238/790) of men reported hving used recretionl drugs before or during sexul intercourse in the previous yer. Over 2% (20/804) of MSM hd dignosis of gonorrhoe during the previous 12 month, in the sme period little less thn 2% (13/804) of MSM hd dignosis of syphilis nd 0.4% (3/804) were heptitis C positive. HIV incidence Between April 2011 nd Februry 2014, 804 MSM were followed for totl of person-yers (rnging from six dys to 2.84 yers). During follow-up, 25 seroconversions were recorded, yielding n overll incidence of 2.80 per 100 person-yers (95% CI: ). From these 25 newly-identified cses, 19 (76.0%) were effectively linked to cre vi CheckpointLX. Of the remining six individuls who did not ccept referrl, three preferred to use their own mens to ccess helth services nd three did not provide informtion on clinicl follow-up. Prticipnts who seroconverted hd men ge of 31.2 (9.4) yers: not significntly different from those who did not (30.2 (8.9) yers, p = 0.598), nd significntly shorter verge followup time thn those who did not seroconvert (0.79 yers vs 1.12 yers, p = 0.018), but pproximtely the sme number of visits, resulting in higher men number of tests per yer (4.8 vs 3.9, p = 0.012) (Tble 2). 5

6 Tble 2 Comprison of follow-up time nd number of visits between prticipnts who seroconverted nd those who did not, cohort of men who hve sex with men, Lisbon, Portugl, (n=804) HIV-positive HIV-negtive p vlue N Minimum nd mximum of follow-up time 56 dys 1.91 yers 6 dys 2.84 yers n.. Men time of follow-up (SD) (yers) 0.79 (0.50) 1.12 (0.68) Men number of visits (SD) 2.76 (1.05) 2.85 (1.21) Men number of visits per yer (SD) 4.8 (3.0) 3.9 (5.6) n..: not pplicble; SD: stndrd devition. p vlue for independent smples, Mnn-Whitney test Predictors of HIV infection Being born before 1970 hd strong point estimte of ssocition, though non-significnt, with seroconversion, wheres the remining bckground indictors hd negligible ssocitions. Vribles tht were directly ssocited with HIV incidence even fter djustment for UAI were: reporting prtner disclosure of HIV positive sttus between first nd the most recent visit (IRR=5.25; 95% CI ; p=0.006); sexul intercourse with HIV-positive men whether only reported t first visit (IRR=3.79; 95%CI ; p=0.026), or only t the most recent visit (IRR=5.99; 95%CI ; p < 0.001); hving hd n HIV-positive stedy prtner t lest once during follow-up (IRR=3.28; 95%CI ; p=0.017); newly-dopted UAI with stedy prtner regrdless of their HIV sttus between cohort entry nd the most recent visit (IRR=3.85; 95%CI ; p=0.018); persistent UAI with occsionl prtners during follow-up (IRR=3.63; 95%CI ; p=0.009) nd hving been newly dignosed with syphilis between cohort entry nd HIV seroconversion (IRR=4.71; 95%CI ; p=0.040). Even though non-significnt, hving hd sex with sex workers t lest once during follow-up (IRR=2.60; 95%CI ; p=0.072) nd newly dopting UAI with occsionl prtners between cohort entry nd the most recent visit (IRR=2.79; 95%CI ; p=0.084) were ssocited with HIV incidence. Crude ssocitions with more generic mrkers of exposure (hving strted to hve sex with men four to eight yers before cohort entry, reporting recent sexul intercourse with bisexul men or women nd persistent use of recretionl drugs during follow-up) lost significnce fter djustments. Detiled results of HIV predictors re presented in Tble 3. We strtified the nlysis of the min determinnts of HIV incidence by HIV sttus of stedy prtner (Figure). Overll, we observed tht MSM who hd n HIV-positive stedy prtner during follow-up hd higher incidence rtes thn MSM who did not hve n HIV-positive prtner. The gretest increses in HIV incidence were found for MSM reporting newly-dopted UAI with stedy prtner (IRR = 17.29; 95% CI: ) nd MSM reporting persistent UAI with occsionl prtners during follow-up (IRR = 14.19; 95% CI: ). Discussion The Lisbon Cohort of MSM provides the first quntifiction of HIV incidence in Portuguese MSM. The overll estimte of 2.80 per 100 person-yers is higher thn those obtined in other Europen settings [4,6,8], nd shows worrying ongoing trnsmission of HIV mong MSM, consistent with routine surveillnce dt [23]. In this cohort, hving n HIV positive stedy prtner incresed the risk of seroconversion, prticulrly fter newly-dopted UAI with tht prtner nd regrdless of UAI with occsionl prtners. The role of serodiscordnt stedy reltionships in newly cquiring HIV infection is well-recognised [24]. Previous studies suggest tht men within stedy reltionship re more likely to engge in UAI nd hve lower rtes of HIV testing s result of lower risk perception nd incresed confidence of remining HIV-negtive [25]. As for the timing of trnsmission, mong MSM who seroconverted nd hd n HIV positive stedy prtner, pproximtely hlf reported their disclosure of HIV (whether previously dignosed or not) during follow-up. This suggests tht substntil frction of trnsmission to the index prtner might occur during the cute infection stge of the stedy prtner, when the risk of trnsmission is highest [26]. Nevertheless, we cnnot exclude the contribution of older infections. Indeed, 37.1% of HIVpositive MSM in Portugl presented to cre with CD4 count < 350/mm3 nd, nd 39.0% either hd detectble or unknown virl lod [27]. Persistent UAI with occsionl prtners ws ssocited with HIV seroconversion, s extensively described [28]. Our study dds tht being newly dignosed with 6

7 Tble 3 Predictors of HIV incidence, cohort of men who hve sex with men, Lisbon, Portugl, (n=804) HIV cses Men number of tests per yer during follow-up PY HIV incidence IRR (95% CI) p vlue IRR (95%CI) p vlue Less thn ( ) ( ) ( ) ( ) ( ) ( ) More thn ( ) ( ) < Bckground chrcteristics Birth cohort Before ( ) n.. n n ( ) n.. n or fter ( ) n.. n.. Country of birth Portugl n.. Other ( ) n.. n.. Eduction (schooling yers) Less thn higher eduction ( 12 yers) ( ) n.. n.. Higher eduction (> 12 yers) n.. Sexul identity Homosexul n.. Bisexul/heterosexul/other ( ) n.. n.. HIV testing Number of HIV previous tests t cohort entry n.. n.. n.. 1 to n.. More thn ( ) n.. n.. Resons for HIV test during follow-up Concerned with exposure to HIV throughout follow-up Never n.. At lest once ( ) n.. n.. Prtner ws dignosed with HIV/disclosed HIV sttus throughout follow-up Persistent No Chnged: Yes to No ( ) ( ) Chnged: No to Yes ( ) ( ) Persistent Yes n.. n.. n.. n.. Sexul life nd prtners Age t first nl intercourse More thn n.. 15 or less ( ) n.. n.. Time since the beginning of sexul life with other men 4 yers or less to 8 yers ( ) ( ) more thn 8 yers ( ) ( ) Role in nl sex Insertive only n.. Receptive/both ( ) n.. n.. IRR: djusted incidence rte rtio; CI: confidence intervl; IRR: incidence rte rtio; n..: not pplicble; PEP: post-exposure prophylxis; PY: person-yers; STI: sexully trnsmitted infection; UAI: unprotected nl intercourse. Adjusted for UAI with stedy prtner nd UAI with occsionl prtners during follow-up. 7

8 Tble 3b Predictors of HIV incidence, cohort of men who hve sex with men, Lisbon, Portugl, (n=804) HIV cses PY HIV incidence IRR (95% CI) p vlue IRR (95%CI) p vlue Sexul life nd prtners Sexul intercourse throughout follow-up with ny of the following: HIV-positive men Persistent No Chnged: Yes to No ( ) ( ) Chnged: No to Yes ( ) < ( ) < Persistent Yes n.. n.. Bisexul men Persistent No Chnged: Yes to No ( ) ( ) Chnged: No to Yes ( ) ( ) Persistent Yes ( ) ( ) Men with different sexul prtners Persistent No n.. Chnged: Yes to No ( ) n.. n.. Chnged: No to Yes ( ) n.. n.. Persistent Yes ( ) n.. n.. Sex workers (even if not pid) Never At lest once ( ) ( ) Women Persistent No Chnged: Yes to No ( ) ( ) Chnged: No to Yes n.. n.. n.. Persistent Yes ( ) ( ) Trios/group sex Persistent No n.. Chnged: Yes to No n.. n.. Chnged: No to Yes ( ) n.. n.. Persistent Yes ( ) n.. n.. Stedy prtner during follow-up Persistent No n.. Chnged: Yes to No ( ) n.. n.. Chnged: No to Yes ( ) n.. n.. Persistent Yes ( ) n.. n.. HIV-positive stedy prtner during follow-up Never At lest once ( ) ( ) Occsionl prtners during follow-up Persistent No n.. Chnged: Yes to No ( ) n.. n.. Chnged: No to Yes ( ) n.. n.. Persistent Yes ( ) n.. n.. Number of occsionl sexul prtners in the previous 12 months t cohort entry < = n.. 2 to ( ) n.. n.. > = ( ) n.. n.. Hving sex for money or drugs during follow-up Never n.. At lest once ( ) n.. n.. IRR: djusted incidence rte rtio; CI: confidence intervl; IRR: incidence rte rtio; n..: not pplicble; PEP: post-exposure prophylxis; PY: person-yers; STI: sexully trnsmitted infection; UAI: unprotected nl intercourse. Adjusted for UAI with stedy prtner nd UAI with occsionl prtners during follow-up. 8

9 Tble 3C Predictors of HIV incidence, cohort of men who hve sex with men, Lisbon, Portugl, (n=804) HIV cses PY HIV incidence IRR (95% CI) p vlue IRR (95%CI) p vlue UAI during follow-up UAI with stedy prtner Persistent No Chnged: Yes to No ( ) ( ) Chnged: No to Yes ( ) ( ) Persistent Yes ( ) ( ) UAI with occsionl prtners Persistent No Chnged: Yes to No n.. n.. Chnged: No to Yes ( ) ( ) Persistent Yes ( ) ( ) Venues used to meet occsionl prtners t cohort entry Only sexul venues (suns, drk rooms, sex clubs) No n.. Yes ( ) n.. n.. Other venues (discos/gy brs, gym nd outdoor cruising venues) No n.. Yes ( ) n.. n.. Internet No n.. Yes ( ) n.. n.. STIs nd heptitis Recent history of syphilis during follow-up Persistent No Chnged: Yes to No ( ) ( ) Chnged: No to Yes ( ) ( ) Persistent Yes Recent history of gonorrhoe during follow-up Persistent No n.. Chnged: Yes to No n.. n.. n.. Chnged: No to Yes ( ) n.. n.. Persistent Yes n.. n.. n.. n.. Lifetime history of heptitis C reported t cohort entry No/does not know n.. Yes n.. n.. Lifetime history of Heptitis B reported t cohort entry No/does not know n.. Yes ( ) n.. n.. Drug use before or during intercourse Use of recretionl drugs before or during intercourse during follow-up Persistent No Chnged: Yes to No ( ) ( ) Chnged: No to Yes ( ) ( ) Persistent Yes ( ) ( ) PEP t cohort entry Does not know bout n.. Knows bout but never used ( ) n.. n.. Knows nd used ( ) n.. n.. IRR: djusted incidence rte rtio; CI: confidence intervl; IRR: incidence rte rtio; n..: not pplicble; PEP: post-exposure prophylxis; PY: person-yers; STI: sexully trnsmitted infection; UAI: unprotected nl intercourse. Adjusted for UAI with stedy prtner nd UAI with occsionl prtners during follow-up. 9

10 Figure Strtified nlysis of the min determinnts of HIV incidence by HIV sttus of stedy prtner, cohort of men who hve sex with men, Lisbon, Portugl, (n=804) IRR (95%CI ) IRR: IRR: IRR: 8.33 IRR: 5.73 IRR: 2.36 IRR: IRR: 2.05 IRR: 2.13 IRR: 3.82 IRR: 1.31 IRR: ref ref Never hd UAI Chnged: Chnged: Yes to No No to Yes Persistent Never hd Chnged: Chnged: Yes UAI Yes to No No to Yes Persistent Never hd Chnged: Chnged: Yes UAI Yes to No No to Yes Persistent Never hd Chnged: Chnged: Persistent Yes UAI Yes to No No to Yes Yes HIV - or no stedy prtner HIV + stedy prtner HIV - or no stedy prtner HIV + stedy prtner UAI with stedy prtner during follow-up UAI with occsionl prtners during follow-up IRR: incidence rte rtio; 95% CI: 95% confidence intervl; UAI: unprotected nl intercourse; ref: reference ctegory. No seroconversions were observed in the ctegory syphilis during follow-up ws strong predictor of HIV incidence, independently of self-reported UAI. An dditionl red flg ws the observtion tht MSM who seroconverted hd shorter intervls between follow-up visits nd higher men number of tests per yer, which highlights the use of testing s risk mngement strtegy. Our findings suggest tht, in ddition to the pttern of service use itself, incident circumstnces (newlydopted UAI with stedy prtner, newly-disclosed HIV-positive prtner, nd newly-dignosed syphilis) my be useful mrkers of the short-term risk of infection. Yet, it is importnt to note tht we cnnot ssume tht ny incident circumstnce or chnge in the informtion provided between visits represents sustined behviourl chnge but rther indictes vrying behviourl options tht my influence seroconversion risk. Other behviourl fctors, such s time since the beginning of sexul life, intercourse with bisexul men or sex workers nd persistently using recretionl drugs, my be regrded s less specific predictors of incident HIV, even though such effects were probbly lrgely medited by UAI. The number of sexul prtners in the yer before cohort entry ws not ssocited with incresed HIV incidence. These findings highlight tht, rther thn extensively chrcterising the type or number of prtners, trgeted inquiries bout UAI in this context seem to be more ccurte for predicting HIV risk. So fr, none of the bckground vribles predicted HIV risk in this cohort of Portuguese MSM. However, higher HIV incidence ws found in MSM born before Older MSM were previously described t higher risk of cquiring HIV from stedy prtner [8] nd my underestimte vulnerbility since they hve remined uninfected up to the present [29]. In contrst with previous studies nd ntionl nd Europen surveillnce dt [5,30], younger MSM were not clerly identified s being t higher risk for HIV, but tht could be relted 10

11 to different ptterns of use of the CheckpointLX by younger genertions. Methodologicl options nd limittions of this study should be ddressed. First, this design option is unlikely to result in representtive smple of the source MSM popultion, which limits the generlisbility of our findings. When compred with dt from the 2007 Ntionl Helth nd Sexulity Survey (HSS) [31], MSM in our smple re younger, more self-identified s homosexul (86.1% vs 35.9% of men reporting some kind of sexul contct with men in the HSS) nd report more frequently history of HIV testing (84.1% vs 61.0% in HSS). Nevertheless, by setting up cohort study in community-bsed voluntry counselling nd testing service we expect to rech MSM on verge t higher risk of infection thn the generl MSM community. Thereby it seems resonble to dmit tht we re focusing our ttention on priority subset of the popultion in terms of HIV risk (even if potentilly more wre thn those not reched by the service). Additionlly, since CheckpointLX promotion strtegies remined similr during follow-up, we do not expect tht the extent of selection bis will chnge substntilly over time, which is prticulrly importnt for estimting seculr trends of infection nd behviours in the source popultion [32-34]. Finlly, the fct tht the recruitment site is service which ims to nticipte dignosis nd to provide evidence-bsed nd dpted informtion my itself modify the risk of cquiring HIV nd the consequent incidence estimtes. However, we expect tht newly-recruited clients reflect the overll incidence of infection in the community. Another importnt issue is prticiption bis: the fct tht round 30% of eligible MSM chose not to enter the cohort implies tht informtive dt my be missing on hrder-to-rech subset of the trget popultion. However, the frequency of prior testing ws similr between groups, suggesting tht both my hve similr perceived risk of cquiring HIV [35]. Moreover, the observed ttrition mens tht informtion bout possible seroconversions is missing in hlf of prticipnts, which is cler limittion. Follow-ups depend on the frequency of service uptke, which cn itself be influenced by perceived risk of infection. Efforts hve been mde to minimise dropout rtes, including ctive reminders of follow-up visits by peer counsellors. However, we still found differences in men ge between MSM who ppered for follow-up nd those who did not, lthough the bsolute difference ws smll. No differences were found in the frequency of behviours ssocited with higher probbility of seroconversion. This leds us to hypothesise tht our incidence rte might not be substntilly ffected by losses to follow-up. Self-reported informtion is lwys subject to limittions in vlidity nd relibility. However, we re confident tht relevnt strength comes from the involvement of community peer counsellors, since this strtegy increses prticiption nd improves vlidity nd completeness of informtion s well s disclosure of risk, s supported by previous reserch [34,36]. Despite the high incidence observed, the bsolute number of infections is still low, resulting in suboptiml sttisticl power for some comprisons. In the future, with lrger smple size nd longer follow-up periods, we expect incresed precision of estimtes. Nevertheless, these first estimtes re importnt for two min resons: i) they drw first picture of HIV incidence nd its drivers in Portuguese MSM bout whom little ws known; ii) they dd evidence on the role of chnges in individul circumstnces in newly cquiring HIV to the existing body of prospective evidence from vriety of settings. In conclusion, we found high HIV incidence in this cohort of Portuguese MSM likely to be driven by short-term contextul nd behviourl chnges, nmely newlydopted UAI with stedy prtner, newly-disclosed HIV-positive prtner nd newly-dignosed syphilis. History of serodiscordnt stedy reltionships nd persistently reporting UAI with occsionl prtners lso plyed mjor role in predicting HIV seroconversion. Acknowledgements The Lisbon Cohort of MSM tems thnks to ll prticipnts, to CheckpointLX tem of peer counsellors: Jesus Rojs, Miguel Roch, Fernndo Ferreir, Nuno Pinto nd Julio Esteves, nd to Din Cosme from ISPUP. Conflict of interest None declred Authors contributions PM drfted the mnuscript nd performed the dt nlysis. RL prticipted in the study design, helped drft the mnuscript, prticipted in nlysis nd interprettion of dt, nd reviewed the mnuscript for importnt intellectul content. CC reviewed the mnuscript for importnt intellectul content. 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