BMC Public Health 2008, 8:180 http://www.biomedcentral.com/1471-2458/8/180 due to repeat visits in the same episode. The main reasons for true non-response were language barriers and low lit- eracy, in particular in migrants from non-European coun- tries, e.g., South America. To overcome this deficit, survey versions in a number of languages have already been developed and are now being administered computer- based with the option to get support from staff. Finally, we were not able to identify survey responses of clients re- attending with new episodes, if any. While this fraction is considered to be negligible given the short observational period, a client tracking system for matching survey responses of the same individual will be implemented in future evaluations. Checkpoint Zurich as a model of comprehensive care for MSM has already been reproduced in other European cit- ies in 2007, e.g., in Munich. Checkpoint Munich is run by the Munich AIDS foundation and offers similar services. Other metropolitan areas, in particular in Germany, are currently adopting the Checkpoint concept to their needs (cities of Cologne, Dresden) or have already reproduced parts of it. For example, the concept of Checkpoint mobile has already been transferred to Berlin. The advantage of this model in comparison to traditional VCT projects is the opportunity to offer diagnosis, therapy and follow-up at the same location through the same team with a consid- erably lower rate of positive tested patients that do not obtain treatment. Our data also provide further evidence that substance use, in particular alcohol consumption, is common amongst MSM. It represents a major threat to MSM health and is likely to play an important role in HIV and STI risk-taking behaviour. These data are confirmed by other national and international studies [16,28,29]. For example, Wang et al. report from a survey study amongst gay men living in the French part of Switzerland that one out of ten gay men reported consuming high daily quantities of alcohol (≥ 60 g/day) in the past 4 weeks and gay men had a more than(threefold adjusted odds ratio of any drug use within the past 12 months compared to the general male popu- lation [12]. Nearly half of the respondents fulfilled the cri- teria for at least one of five DSM-IV disorders (12 month prevalence: major depression (19.2%), specific phobia (12.6%), social phobia (13.5%), alcohol dependence (11.4%), drug dependence (7.3%)) [13]. These data are deeply worrying. Hence, concepts for psychosocial screen- ing and counselling are currently being developed to counteract substance abuse in the MSM community. Conclusion In contrast to common concepts of "testing clinics", the Checkpoint service also provides post-exposure prophy- laxis, HIV and STI treatment, psychological support and counselling and general medical care. It thus follows a holistic approach to health in the MSM community with the particular aim to serve as a "door opener" between the established system of care and those men that have no access to, or for any reason hesitate to utilize, traditional health care. Mobile testing services and interventions for issues other than HIV and STI are consequently expanded to reach high-risk populations and target other health concerns and high prevalence of mental disorders amongst MSM. Competing interests The authors declare that they have no competing interests. Authors' contributions DLBS and PB conceived of the study and participated in its design. PB coordinated the study group. DLBS performed the statistical analysis. 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