Lisbon MSM Cohort




The Lisbon MSM Cohort is an observational study, designed as a prospective open cohort, started in April 2011 in a partnership with CheckpointLX/GAT and the Institute of Public Health of the University of Porto. The study has the following main objectives:


1) From the perspective of quantifying the burden of disease and prevention:


  • To know the dynamics of HIV infection among Men who have sex with Men (MSM) in Portugal by estimating its incidence;
  • To monitor primary and secondary prevention behaviors, including condom use, frequency and reasons for testing and the use of post- and pre-exposure prophylaxis;
  • To identify critical points for preventive interventions.


2) From the perspective of health care delivery:


  • To identify strategies to continuously improve the provision of testing;
  • To explore strategies to ensure timely linkage to care of those who have a reactive test.


The cohort recruits a consecutive sample of CheckpointLX clients – an anonymous/confidential, free service for rapid HIV testing for MSM delivered by peer counselors. Men who have a non-reactive test, aged 18 or older, who report having had sex with other men, are eligible to participate in the prospective study. Follow-up visits are scheduled according to their convenience, ideally at every six months.


At each visit a structured questionnaire about health-related behaviors is administered and a rapid HIV test is performed. Syphilis and Hepatitis C test are also offered according to predefined criteria.  Pre- and post-test counseling is offered and, in case of a reactive result, a referral is made for an HIV/infectious disease clinic. The study is compliant with the ethical principles of the Helsinki Declaration. All participants give their written informed consent prior to inclusion. The study protocol was approved by the Ethics Committee of São João Hospital and Medical School, University of Porto (ID 104/12).


At the national level the follow-up of this cohort of HIV-negative MSM is a valuable tool for the dynamic monitoring of HIV infection in a scenario where existing prospective information has been very limited. Within the international context it also allows for a more in-depth analytical approach on population time trends and individual changes in risk factors shaping the epidemic among MSM.


In 2020, the Lisbon Cohort of Men who have sex with men (MSM) performed 3404 interviews with adult MSM, of which 828 were entry interviews in the cohort.

49 reactive tests for the Human Immunodeficiency Virus (HIV) were identified.

111 reactive cases have also been identified for antibodies to syphilis and 8 for antibodies for hepatitis C virus.

No reactive case has been identified for surface of the hepatitis B virus.

The cohort results were published in 2020 in two scientific papers, two oral communications at international congresses, and at a national meeting dedicated to men's sexual health.

The study is conducted at CheckpointLX - a community-based center, directed to MSM, for fast, confidential and free screening for HIV and other sexually transmitted infections, counseling and referral to health care. Screenings and Interviews with participants are carried out by trained technicians, who are also MSM.