title: Who is omitted from repeated offline HIV behavioural surveillance among MSM? Implications for interpreting trends.
abstract: Repeated behavioural surveillance should sample all epidemiologically relevant subgroups to provide a complete picture of trends in HIV risk behaviours. Web-based recruitment has been mooted but little empirical data exist on country experiences. We describe who is omitted from three rounds of a conventional offline-only surveillance programme among men who have sex with men (MSM) 2006-2011, but recruited subsequently on Internet dating sites, and the implications of this for understanding trends. The latter were younger, less gay identified and less gay community attached. Importantly, they reported different partnering patterns, lower condom use with casual and fuckbuddy-type male partners, and lower rates of HIV testing, compared to MSM routinely captured in offline surveillance. The replacement of offline socio-sexual activity by the Internet among many MSM means that current venue-based surveillance systems may underestimate risk behaviours, overlook trends among unsampled online MSM, and misinterpret trends observed in sampled MSM due to "sample drift" of most-at-risk MSM.
authors.affiliation: AIDS Epidemiology Group, Department of Preventive and Social Medicine, University of Otago, PO Box 913, Dunedin, New Zealand, peter.saxton@otago.ac.nz.
authors.forename: Peter
authors.initials: P
authors.lastname: Saxton
authors.forename: Nigel
authors.initials: N
authors.lastname: Dickson
authors.forename: Anthony
authors.initials: A
authors.lastname: Hughes
mesh_terms: D000293:Adolescent; D000328:Adult; D003430:Cross-Sectional Studies; D015658:HIV Infections / Q000453:epidemiology* / Q000517:prevention & control; D018451:Homosexuality, Male / Q000706:statistics & numerical data; D006801:Humans; D020407:Internet; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D009520:New Zealand / Q000453:epidemiology; D018579:Patient Selection; D011159:Population Surveillance / Q000379:methods; D012307:Risk Factors; D012725:Sexual Behavior / Q000706:statistics & numerical data*; D012747:Sexual Partners; D060756:Social Networking; D011795:Surveys and Questionnaires