Tuberculosis (TB) is the main opportunistic infection and the main cause of death in people living with HIV (PLHIV). Brazil is among the 30 countries with the highest TB/HIV burden worldwide and the disease is responsible for about 1 3 % of all deaths in PLHIV in the country. Brazil is committed to the goals stated by international organisations and launched The National Plan to end TB , highlighting some of the main challenges that need to be overcome in the next 18 years . These include the expansion of gene Xpert for the diagnosis of TB, the introduction of new technologies for TB diagnosis and treatment and the strengthening of policies for TB control in PLHIV. The aim of the present study was to evaluate the cost - effectiveness of a protocol for TB diagnosis in PLHIV in Brazil. Four specific objectives were identified in order to achieve this aim: (1) to perform a review of the literature to evaluate gaps in costing studies and economic evaluations addressing TB/HIV co - infection; (2) to estimate the costs of PLHIV , with or without active or latent TB, from the symptomatic phase until the first year of treatment from the perspective of the Brazilian public health system; (3) to estimate direct and indirect costs of TB/HIV and latent TB/HIV co - infection ( LTBI /HIV) from the patient perspective during the pre - diagnosis and treatment period; and (4) to perform an interim analysis of the cost - effectiveness of a protocol for TB diagnosis in PLHIV as part of a pragmatic clinical trial in Brazil . The literature review shows a gap in the scientific evidence on cost and cost - effectiveness of TB diagnosis in PLHIV, with a concentration of studies in African countries. The cost study from the health system perspective shows that TB/HIV co - infected patients incurred in higher costs when compared with HIV/AIDS and LTBI /HIV patients for the whole pathway of care. The total mean cost for the TB/HIV category was almost 6 times higher than the HIV or AIDS category (US$ 6, 210 vs US$ 1, 612). The cost study from the patient perspective indicates that TB/HIV co - infected patient s can face catastrophic costs during the diagnosis and treatment period, with indirect costs representing a higher proportion of total costs , at 52.4%. The modelling study suggests that the protocol for TB diagnosis in PLHIV, including screening by clinical algorithm and complementary tests, such as gene Xpert is a cost saving intervention when compared with routine hospital referral. The findings from this study can contribute to supporting strategies to improve TB diagnosis in PLHIV, reducing costs from the health system perspective and preventing catastrophic costs faced by TB/HIV patients