Routine testing to detect HIV infection is an important measure for a combined HIV prevention strategy  since it entails three levels of intervention. First, a biomedical level, since technology is used to detect the virus, and is the gateway to antiretroviral treatment, breaking the chain of transmission . Second, a behavioral and cultural level, embedding individual and group decisions to test in a psycho-social matrix of sex, risk and prevention . Finally, successful testing depends not only on the availability of the test, but also on overcoming barriers such as stigma and discrimination when accessing testing services [4, 5].
Unawareness of HIV status impacts on access to antiretroviral treatment (ARV) and consequently on higher viral loads, a potential factor for HIV transmission . In many countries, men who have sex with men (MSM) are disproportionately affected as they face much higher rates of HIV and AIDS than the general population . In the United States of America (USA), the number of people living with HIV (PLWH) who do not have suppressed viral loads is higher among MSM compared to male and female heterosexuals .
In Latin America, there are 1.9 million PLWH and 80% of these knew their status in 2018 . It has been estimated that in Brazil there are 900,000 PLHIV and that approximately 135,000 PLHIV are unaware of their serostatus. This corresponds to 85% of the 90% target of the initial target of the 90-90-90 UNAIDS goals for PLHIV  .
A survey using RDS among MSM in 12 state capitals in 2016 indicated that Brazilian MSM knowledge of HIV serostatus is low. Among those who tested for HIV in the study, 44% had not been aware of their positive status . A similar RDS study, conducted in 2009 in 10 cities around the country demonstrated that almost half (48%) of MSM had never previously tested for HIV . In a comparison between the 2009 and 2016 surveys, there was a drop in the proportion of MSM who had never tested, from 49.8% in 2009 to 33.8% in 2016, and an increase in the proportion of those who tested during the previous 12 months, from 21.2% to 43.3% . In Salvador, a capital city in the country’s most impoverished region (Northeast), in the 2009 survey, 62.8% of MSM reported they had never tested for HIV . In Curitiba, a city in a high-income region (South), in another survey among MSM in 2015, the proportion never tested was much smaller: 24.3% , demonstrating important geographical disparities in rates of HIV testing among MSM in Brazil.
In Brazil, free access to HIV test occurs mainly in specialized services (e.g. testing and counseling centers, clinics and hospitals). Recently, HIV test is available in Primary Health Care (PHC) clinics of the Brazilian National Health System (SUS) . However, the benefit of this program is mainly for pregnant women , and the coverage among sexual minorities remains low [18, 19]. Stigma and discrimination towards MSM in Brazil are high and one of the barrier to access health care services and HIV test especially at PHC [20–22]. Therefore, it is necessary to expand novel ways of HIV testing among MSM. One way is HIV self-testing (HIVST). It has been introduced in many countries, including Brazil, following a recommendation from the World Health Organization in 2016 . HIVST is simple, easy to use, allows the individual to carry out the test, can use oral fluid or blood sample, and the interpretation of results may be undertaken with or without help from a trained individual . This test procedure should be largely available as complementary to other available options .
HIVST guarantee confidentiality and privacy [25, 26]. By enabling testing outside the health services, for example, in the homes, in social venues, and sex work situations, HIVST decentralizes testing and strengthens people’s autonomy [23, 27]. Furthermore, it may facilitate an increase in testing frequency among individuals at high risk of HIV infection and in populations groups with less frequency of testing in traditional services . A meta-analysis showed that HIVST doubled uptake of testing among men, frequency of testing among MSM, and the likelihood of an HIV-positive diagnosis . HIVST also could have positive impacts on HIV care as it allows for rapid detection and enables early treatment initiation, which can reduce the number of HIV-related clinical visits  and can potentially reduce the spread of HIV infection through test and treat [2, 30, 31], and increased HIV risk perception .
There are few studies on the acceptability of HIVST in middle-income countries . In Latin America, an RDS survey in Argentina have showed that 74% of the MSM was likely to buy an HIVST at a pharmacy for use at home  In Brazil, a cross-sectional online survey in 2011 among MSM previously tested HIV negative estimated that 47% reported a preference for an HIVST at home , and more recently two cross-sectional online surveys carried out on a sample of MSM users of hookup apps from five Brazilian regions, estimated that HIVST awareness ranged from 26.0% in 2016 to 33.0% in 2017, and willingness to use from 50.0% to 42.0%, respectively . Although these studies have accessed HIVST acceptability by MSM, few have explored how previous testing experiences differs in its associated factors with acceptability, especially among those who were never tested as compared to those who had a previous HIV negative result. Both groups could potentially benefit from access to additional testing services . Moreover, there are no studies of HIVST acceptability among a large population sample of Brazilian MSM. Therefore, this article aims to estimate the acceptability of HIVST among MSM from 12 Brazilian cities and to investigate factors associated with acceptability among those who had never been tested or had a previous HIV negative result.