Ti et al. BMC Public Health 2012, 12:189 http://www.biomedcentral.com/1471-2458/12/189 In addition to being enrolled in voluntary drug treat- ment, being enrolled in the tenofovir trial was also posi- tively associated with HIV testing among IDU. The tenofovir trial in Thailand, sponsored by the US CDC, was launched in 2005 in an attempt to examine the safety and efficacy of this antiretroviral drug. Currently, tenofovir (alone) is being provided to approximately 2,400 HIV-negative IDU and 17 drug treatment clinics across Bangkok [30]. Results of the US CDC-sponsored pre-exposure prophylaxis trial in Thailand are to be revealed in early 2012 [31]. The increased odds of HIV testing among IDU in the tenofovir trial could be attrib- uted to the fact that all participants in the trial receive free rapid HIV testing on an ongoing basis. Although our findings show a positive association between being enrolled in the tenofovir trial and HIV testing, concerns have been expressed over the fact that the trial sites in Thailand failed to provide sterile syringes and needles to IDU participants [32,33]. Efforts to engage and consult with IDU community groups at an earlier stage of the trial design process may have helped alleviate these con- cerns and should be considered for future HIV preven- tion trials as a means of ensuring appropriate access to HIV prevention technologies among trial participants. Internationally, peer outreach and peer-run initiatives have been shown to be successful in extending the reach and effectiveness of conventional public health programs, including those focused on preventing and treating HIV/AIDS among IDU [14,34,35]. Since the launch of Thailand’s 2003 “War on Drugs” campaign, the government has continued to rely on repressive approaches to drugs, including arbitrary arrests, black- listing, drug planting by police, extrajudicial executions and other human rights violations of people involved with drugs [11,36,37]. In this context, severe stigma and discrimination persist against Thai IDU, prompting many to avoid public health programs [37]. Additionally, problems related to stigmatizing attitudes of health care providers focused on IDU have been reported among Thai health professionals, including nursing students, which in turn likely adversely affects the willingness of IDU to access health care [38]. Given these problems, the noted effectiveness of various peer-based methods for IDU, and the high willingness to access HIV testing at the MSHRC, peer-based HIV testing interventions for IDU may have high potential for success in this setting. In the present study, having been to the MSHRC pre- viously was significantly and positively associated with willingness to get HIV testing at the centre. In an earlier study conducted on the MSHRC, results showed that the main reason IDU did not access the centre was the lack of knowledge of its existence [16]. Therefore, future efforts should focus on increasing awareness of and Page 7 of 9 improving access to the MSHRC and other drop-in cen- tres like it. Since the focus of this paper was on willing- ness to get HIV testing at the MSHRC without specifying whether the testing was peer-delivered, future research efforts should seek to determine whether IDU would be willing to be tested by a peer either in the context of a drug-user-run harm reduction program or in other conventional health care settings. Enrolment in voluntary drug treatment was also asso- ciated with willingness to get HIV testing at the MSHRC. As mentioned above, there was an interaction effect involving enrolment in voluntary treatment and gender, and willingness to get tested at the MSHRC. Among participants who were not enrolled in voluntary treatment, males were significantly more willing than females to get tested at the MSHRC, although this asso- ciation did not reach conventional significance. Among female IDU, those engaged in treatment were signifi- cantly more willing to get tested at the MSHRC com- pared to those out of treatment. In light of these findings, future research should seek to unpack the gen- der dynamics surrounding addiction treatment enrol- ment and HIV testing behaviour within this setting. This study has several limitations. First, because of the cross-sectional nature of the study, there is an inability to determine a temporal relationship between exposure and outcome, and therefore causation cannot be inferred. Second, the data collected were self-reported and may be subject to reporting biases. Socially desirable reporting as well as recall bias may affect reports of both risk behaviour and testing behaviour. Third, since the study sample was small and not randomly selected, the study may not be representative of Thai IDU. As well, our findings may not be generalizable to other popula- tions of IDU. Lastly, because of the small sample size, there were wide intervals around some of the estimates reported. Conclusions In the present study, we found high rates of HIV testing among Thai IDU. However, we found that among parti- cipants who were not tested for HIV, a high proportion had recently engaged in some form of HIV risk beha- viour. We also observed a high rate of willingness to get free HIV testing at the MSHRC. Willingness to be tested was independently associated with having been to MSHRC, and among women, having been enrolled in voluntary drug treatment was also associated with will- ingness to be tested at the MSHRC. These findings highlight the need for ongoing educational efforts related to HIV transmission, as well opportunities to expand harm reduction strategies to include peer-led HIV testing for IDU in Thailand.