HUMAN immunodeficiency virus (HIV) infection is a potent risk factor for tuberculosis (TB). Not only does HIV increase the risk of reactivating latent Mycobacterium tuberculosis (MTB) infection,¹ it also increases the risk of rapid TB progression soon after infection or reinfection with MTB.^2,3 In persons infected with MTB only, the lifetime risk of developing TB ranges between 10% and 20%.^4,5 In persons coinfected with MTB and HIV, however, the annual risk can exceed 10%.^1,6,7 The TB burden in countries with a generalized HIV epidemic has therefore increased rapidly over the past decade, especially in the severely affected countries of eastern and southern Africa.^8-12 Tuberculosis is one of the most common causes of morbidity and the most common cause of death in HIV-positive adults living in less-developed countries,^13-26 yet it is a preventable and treatable disease.

Background: Respondent-driven sampling is a novel variant of link-tracing sampling for estimating the characteristics of hard-to-reach groups, such as HIV prevalence in sex workers. Despite its use by leading health organizations, the performance of this method in realistic situations is still largely unknown. We evaluated respondent-driven sampling by comparing estimates from a respondent-driven sampling survey with total population data. Methods: Total population data on age, tribe, religion, socioeconomic status, sexual activity, and HIV status were available on a population of 2402 male household heads from an open cohort in rural Uganda. A respondent-driven sampling (RDS) survey was carried out in this population, using current methods of sampling (RDS sample) and statistical inference (RDS estimates). Analyses were carried out for the full RDS sample and then repeated for the first 250 recruits (small sample). Results: We recruited 927 household heads. Full and small RDS samples were largely representative of the total population, but both samples underrepresented men who were younger, of higher socioeconomic status, and with unknown sexual activity and HIV status. Respondent-driven sampling statistical inference methods failed to reduce these biases. Only 31%–37% (depending on method and sample size) of RDS estimates were closer to the true population proportions than the RDS sample proportions. Only 50%–74% of respondent-driven sampling bootstrap 95% confidence intervals included the population proportion. Conclusions: Respondent-driven sampling produced a generally representative sample of this well-connected nonhidden population. However, current respondent-driven sampling inference methods failed to reduce bias when it occurred. Whether the data required to remove bias and measure precision can be collected in a respondent-driven sampling survey is unresolved. Respondent-driven sampling should be regarded as a (potentially superior) form of convenience sampling method, and caution is required when interpreting findings based on the sampling method.

Tuberculosis is a leading cause worldwide of morbidity and mortality among HIV-infected people. The HIV era has seen a dramatic increase of the tuberculosis case fatality rate (CFR) in high HIV prevalence populations. Providing care for HIV-infected people must include measures to tackle this high tuberculosis CFR. To analyse the extent of the increased tuberculosis CFR in high HIV prevalence populations in sub-Saharan Africa, the reasons for this increase and the causes of death, in order to identify possible ways of tackling this problem. References were obtained by searching the MEDLINE on ‘tuberculosis', ‘HIV infection', and ‘mortality’ (MesH or textword). In addition, available data from National Tuberculosis Programme reports were reviewed. Tuberculosis CFR is closely linked to HIV prevalence. Limited autopsy data suggest that death from HIV-related diseases other than tuberculosis is probably the main reason for the increased CFR in HIV-infected tuberculosis patients. Among HIV-infected tuberculosis patients, the higher tuberculosis CFR in sputum smear-negative and extrapulmonary than in sputum smear-positive tuberculosis cases can also be attributed to misdiagnosis of HIV-related diseases as tuberculosis. The adverse effect of the HIV/AIDS epidemic on general health service performance probably accounts for the higher tuberculosis CFR among HIV-negative tuberculosis patients in high prevalence populations than that in low HIV-prevalence populations. Tackling the problem of the increased tuberculosis CFR in high HIV prevalence populations requires collaboration between tuberculosis control and HIV/AIDS programmes in implementing measures such as improved health services, tuberculosis and HIV control services, preventive treatment for HIV-related diseases and anti-HIV treatment.

The General Population Cohort (GPC) was set up in 1989 to examine trends in HIV prevalence and incidence, and their determinants in rural south-western Uganda. Recently, the research questions have included the epidemiology and genetics of communicable and non-communicable diseases (NCDs) to address the limited data on the burden and risk factors for NCDs in sub-Saharan Africa. The cohort comprises all residents (52% aged ≥13years, men and women in equal proportions) within one-half of a rural sub-county, residing in scattered houses, and largely farmers of three major ethnic groups. Data collected through annual surveys include; mapping for spatial analysis and participant location; census for individual socio-demographic and household socioeconomic status assessment; and a medical survey for health, lifestyle and biophysical and blood measurements to ascertain disease outcomes and risk factors for selected participants. This cohort offers a rich platform to investigate the interplay between communicable diseases and NCDs. There is robust infrastructure for data management, sample processing and storage, and diverse expertise in epidemiology, social and basic sciences. For any data access enquiries you may contact the director, MRC/UVRI, Uganda Research Unit on AIDS by email to mrc@mrcuganda.org or the corresponding author.