TAHOD is a collaborative observational cohort study involving 17 participating clinical sites in the Asia and Pacific

region (see Acknowledgements). Detailed methods are published elsewhere [8]; briefly, each site recruited approximately 200 patients, both treated and untreated with antiretroviral therapy; recruitment was based on a consecutive series of patients regularly attending a given clinical site from a particular start-up time; Ethics Committee approval for the study was obtained from the University of New South Wales Human Research Ethics Committee and from a local ethics committee for each participating TAHOD site. The following data were collected: (i) patient demographics and baseline data: date of the clinical visit, age, sex, ethnicity, exposure find more category, date of first positive HIV test, HIV-1 subtype, and date and result of hepatitis B, hepatitis C and syphilis serology; (ii) stage of disease: CD4 and CD8 cell count, HIV viral load, prior and new AIDS-defining illnesses, and date and cause of death; (iii) treatment history:

prior MG-132 concentration and current prescribed antiretroviral treatments, reason for treatment changes and prophylactic treatments for opportunistic infections. The reasons for treatment change were coded as treatment failure, clinical progression or hospitalization, patient decision or request, compliance difficulties, drug interaction, adverse events and other reasons. TAHOD patients were included in the analysis if they were naïve to antiretroviral treatment, and had initiated treatment with triple or more combination therapy since 1996. Treatment failure was defined using WHO guidelines for antiretroviral therapy for adults and adolescents [3]. The guidelines include definitions according to immunological, virological and clinical status to guide modification of treatment: CD4 cell count: after 6 months of therapy, a CD4 cell count below the pretreatment level, or a 50% decline

from the on-treatment peak CD4 cell count, or three consecutive CD4 counts below 100 cells/μL; The date of treatment failure was identified from the database according to the HAS1 WHO guidelines. The earliest failure was included for patients with more than one type of failure during treatment. TAHOD sites were grouped into low (low and lower-middle) and high (upper-middle and upper) income categories according to the gross national income per capita from The World Bank [9]. Modification of antiretroviral treatment following treatment failure was defined as a change to (adding, stopping or substituting) at least one drug in the treatment combination received at the time at which treatment failure was identified. A treatment modification with a duration of 14 days or less was ignored.