HIV is a widespread pathogen with more than 5000 daily infections worldwide [1]. Transgendered women (TGW) are particularly vulnerable. They are a diverse group of people who were assigned male sex at birth but mostly identify as women, trans women, and/or transfeminine. They are estimated to be more than 48 times more likely to be infected with HIV than cis women (those whose gender identity matches that assigned at birth) of reproductive age ^{[2][3][4][5][6][7][8][9][10]}[2,3,4,5,6,7,8,9,10]. Transgender women of color in particular face high rates of infection and low use of important HIV prevention tools ^[10][11][10,11]. A randomized study conducted by Mujugira et al. that included a group of high-risk HIV-infected sex workers including TGW found that more than 80% of respondents feared HIV infection [12]. The number of youths living with HIV in the United States (US) is increasing, and the epidemic is growing among racial, ethnic, and sexual minorities. Reports show that 69% of new infections occur in young men who have sex with men (MSM) and young TGW, and the epidemic is more severe among black and Hispanic youth ^{[13][14][15][16][17][18][19]}[13,14,15,16,17,18,19]. HIV prevalence among TGW is estimated to be approximately 14.2%, which is higher compared to other vulnerable populations such as gay, bisexual, and other men who have sex with men (10.6%) ^[19][20][21][19,20,21]. Additionally, a similar trend is observed for TGW in the Middle East and North Africa, where infection rates continue to rise ^[5][9][5,9]. However, results from a study in São Paulo, Brazil, indicate an even higher prevalence of HIV among TGW compared to data from around the world ^[2][22][2,22]. The estimated prevalence of HIV infection in TGW worldwide is approximately 19.1% [2].

Attempts are made around the world to combat the HIV epidemic through increased emphasis on the prevalence of HIV testing, especially among high-risk populations [23]. U.S. Centers for Disease Control and Prevention and WHO guidelines recommend that people at increased risk for AIDS be tested for HIV infection at least once a year, and in some situations every three to six months ^{[12][24][25][26]}[12,24,25,26]. There are several ways to test for HIV infection, such as traditional testing performed at a clinic, self-testing without visiting a physician or clinic, and HIV testing and counseling for couples [27]. HIV self-testing (HIVST) involves a person being able to take a rapid diagnostic test in private, without a third party, which makes it convenient and can provide discretion. Rapid tests are made from a patient’s saliva and, because of their high sensitivity and specificity, have been approved for individual use by the U.S. Food and Drug Administration (FDA) due to their potential to diagnose new cases of HIV ^[23][28][23,28]. A screening test should be sensitive and specific and, above all, easy to perform. It is important to promote such testing among vulnerable groups to raise awareness and ensure their safety. This is the aim of UNAIDS 95-95-95, where 95% of people living with HIV should be aware of it, 95% of these people should take antiretroviral therapy, and even 95% with this therapy should achieve virological suppression by 2030 [29]. For example, in one of the studies it was observed that a small number of participants in a study conducted in Bangkok who tested HIV-positive were aware of their HIV infection. This finding highlights the need for greater access and more frequent HIV testing, especially in key populations such as TGW [24]. However, a global review of the latest literature shows that there is still a lack of European evidence on transgender people and their HIVST [29].

2. Definition and Types of Tests

HIV self-testing (HIVST) has emerged in recent years as a promising risk reduction strategy. It aims to reduce the HIV epidemic [30]. In particular, it aims to show that HIVST is an easy, convenient, and highly acceptable testing alternative for a variety of key populations around the world ^[30][31][30,31]. This includes populations that may not have access to safe and affordable testing services, including TGW who do not consistently use protection during intercourse ^{[30][32][33][34][35][36][37][38][39]}[30,32,33,34,35,36,37,38,39]. For such TGW, HIVST kits can be used as an active form of risk reduction. A quick, home-based HIV test involves collecting oral fluid to detect the presence of HIV antibodies. Individuals swab their gums with the testing device and place the secretion-soaked tip into the prepared solution. After waiting about 20 min, the result can be read [40]. The research findings suggest that the oral fluid-based HIVST test is preferred over blood-based tests ^[34][41][42][34,41,42]. One of the testing systems developed is HemaSpot-HF. It contains a small plastic device, and you may use it yourself at home to perform the test. After collecting blood (3–5 drops) with a disposable safety puncture device, the HemaSpot-HF can be closed and sent immediately as the desiccant dries the sample inside the cartridge. Study participants sent completed kits directly to the research laboratory using a prepaid return envelope. HemaSpot-HF was developed to solve the technical problems associated with using traditional filter cards to collect a dry blood spot [43]. Studies have shown that men living with HIV are willing and able to collect their own blood samples using HemaSpot-HF and may prefer this option over collecting blood during clinic visits because it provides convenience and privacy ^[43][44][45][43,44,45]. The availability of HIVST kits has been shown to contribute to more frequent partner testing ^{[30][33][35][46][47]}[30,33,35,46,47]. Currently, little is known about the ways in which TGWs communicate with potential sexual partners about HIVST. Research suggests that offering HIVST to sexual partners may be more effective when kits are introduced in the context of dual or couples testing ^{[30][33][38][47][48][49]}[30,33,38,47,48,49]. Tests that already need to be carried out in the laboratory include ribonucleic acid (RNA) tests in blood plasma starting on day 7, p24 antigen (Ag) after 10 days, and antibody-based tests (Ab) about 28 days after infection [50]. Using tests that can detect both Ab and p24 reduced the time required. Most RTs are as effective as fourth generation ELISAs ^[50][51][50,51]. A Polish study shows that the only available option for HIV diagnosis in diagnostic laboratories is generally available for the detection of HIV-1 and HIV-2 antibodies, based on the ELISA method, which is currently being carried out in the laboratory [52].

3. Does TGW Know and Apply HIV Tests?

Despite the large problem of HIV infection, the frequency of HIV testing in the trans population is unsatisfactory [53]. Many TGW postpone medical consultation and come in only with very serious medical conditions [50]. The low rate of HIV testing in TGW ^[50][54][50,54] indicates the need to find new strategies for testing this population. Outreach programs where health services reach out to communities for HIV screening have proven to be an effective service in reaching at-risk populations, including persons providing sexual services ^[50][55][50,55]. TGW who were reached by community-based HIV services and received HIV education were more likely to undergo a recent HIV test [8]. One study found that TGWs who stated they were unlikely to be HIV positive and who always used condoms with non-commercial male partners were less likely to take the test. Theis study did not capture how or why these characteristics are associated with not testing for HIV. Other studies have found that fear of HIV test results, the associated stigma ^[8][56][8,56], and the tendency among transgender communities to believe that they are not at risk for HIV infection were responsible for non-testing [8]. One of the few studies of European residents found that transgender people face significant barriers to HIV testing services, which may be due to the limited dissemination of HIVST information [29]. In the United Kingdom, nearly 50% of the 500 trans participants admitted that they had never had such a test in their lives [57]. Similar results were found in a study conducted in Thailand, where 53.4% of TGW had never had an HIV test ^[8][58][8,58]. Nonprofit facilities were the most common location to obtain HIV testing and counseling services. This preference confirms previous research in Cambodia, which indicates that community-based services are preferred by TGW and other key groups such as sex workers and MSM ^{[8][59][60][61]}[8,59,60,61]. Despite the wide availablity of free HIV testing services, one in five TGWs in the nationwide survey had never taken an HIV test in their lives, and about half had not been tested in the past six months [8]. Similar results were found in a nationwide survey conducted in the United States where 22.8% of respondents had never had an HIV test, with no significant differences between trans male and trans women ^[8][53][8,53].

4. Motivating and Demotivating Factors for Self-Testing

From the study conducted using web-based information, it was shown that reaching young black TGW with adapted information regarding optimal HIV testing options had a significant impact on HIV testing rates. Once such information was provided, testing rates increased among the study population. These results confirm that interventions are required that actually require minimal effort to inform potential infected persons about testing to disseminate HIV testing [27]. Shresta et al. (2020) studied factors influencing the willingness to undergo HIV self-testing among Malaysian TGWs. Almost half of the participants (47.6%) expressed a willingness to selftest. This willingness, in a multivariate analysis, was positively associated with having experienced sexual assault in childhood, having ever used a cell phone or app to find sex clients, and having had intercourse without condoms in the past six months. Interestingly, it was noted that a willingness to selftest was negatively associated with the presence of depressive symptoms or having more daily clients [62]. The motivation for taking an HIV test is having anal sex without a condom or condom failure. Another motivation is not remembering the details of the last sexual episode, lack of confidence in the partner’s health status, and also having sex without condoms. More frequent willingness to test was observed when there was a large number of sexual partners or frequent sex without condoms. Testing both partners before intercourse without a condom is also a noticeable trend [63]. The above-mentioned motivations for HIVST may apply to both transgender and cisgender people, women and men to the same extent. The paper by Iribarren et al. describes TGWs’ experiences with HIV self-testing. Participants gave reasons for refraining from HIV testing in the past. The most commonly reported were availability of testing (men lack of knowledge of where and how to get it) and cost. One-fifth of the respondents had never thought about testing for HIV before. The same number of participants stated that they prefer to take the test at a clinic. Other reasons included fear of a positive result, willingness to test with blood, uncertainty of their partner’s reaction to the test result, or a positive test result in their partner [64].

5. Advantages of Self-Testing

HIVST has been shown to be safe and effective in increasing HIV testing rates without affecting condom use, social protection, or treatment inclusion ^[65][66][65,66]. Home testing provides easy access for high-risk individuals who rarely get tested [13]. Global studies have also shown that no serious side effects associated with HIVST have been reported ^[41][67][68][41,67,68]. One obstacle to HIV testing is stigma, but the convenience and confidentiality provided by HIST may make it an attractive option for TGW. In addition, individuals who test negative may be associated to other HIV prevention methods, such as pre-exposure prophylaxis [69]. One study found that among those who had sought testing in the past, 47% preferred home testing over testing in a clinical setting. Acceptability of home testing was 90% among those who rarely tested, underscoring the importance of home testing, especially in at-risk populations who may not have access to clinic testing for a variety of reasons ^[13][70][13,70]. There is evidence that HIV testing at higher frequency is related to a lower risk of HIV infection and is an effective regimen for reducing HIV infection rates ^[71][72][73][71,72,73]. Other studies have found that getting tested before sexual intercourse reinforces sexual decision making, by forgoing or limiting sexual acts or insisting on condom use with HIV-positive people ^[74][75][74,75]. Some studies have shown that strengthening the position is a benefit of HIVST use ^{[74][76][77][78][79]}[74,76,77,78,79]. A large, randomized trial did not show that HIVST use results in better adherence to pre-exposure prophylaxis, yet HIVST was well tolerated and used as a part of prophylaxis for self-testing and testing with sexual partners [12]. A TGW study in New York City and San Juan, Puerto Rico found that of 368 individuals, only 6 (<2%) did not test themselves or their partners. This shows that ST acceptability was extremely high in the study population of interest. Furthermore, study participants showed high motivation to use self-testing, given that not only did 78% of those in the intervention group (they had access to free self-testing) use self-testing kits, but also 13% of participants in the control group (they did not receive self-testing from the organizers) found a way to obtain self-testing. Furthermore, 76% of participants in the intervention group were able to get a potential sexual partner to selftest. This indicates that the dissemination of selftests through networks has important potential to complement and potentially increase the reach of formal outreach programs. Findings suggest that participants’ willingness to use HIVST is highly dependent on predictors of their partners’ reactions to the test proposal ^[30][80][30,80]. Another advantage of sexual partner self-testing was the detection of HIV in individuals who, despite awareness of HIV infection, engaged in unsafe intercourse without first informing their partner about HIV. Sexual partner self-testing also carried with it support in case of a positive result and an attempt to maintain further contact [75]. MSM and TGW participated in a qualitative study conducted in the Philippines and most of them reported that HIST was convenient and time saving. In addition, some informants described HIST as “discreet” and “very confidential” [81]. TGW in particular may associate clinical testing with stigma and lack of privacy ^[74][76][82][74,76,82], and having HIVST may increase their sense of control over the testing process ^[74][83][74,83].