Mortality in smear-negative tuberculosis patients in Phalombe

In two hospitals in Malawi, where HIV prevalence among tuberculosis patients is 80-90%, the treatment outcome in patients registered with smear-negative pulmonary tuberculosis was determined in relation to chest x-ray (CXR) findings and certain laboratory parameters. Of 70 patients who were registered and treated, 32 (46%) were known to have died. Mortality was particularly high in those with a normal / minimally abnormal CXR (62%) and in those with a white cell count of less than 3.5 × 109 /l (77%). The reasons for this high mortality among patients with smear-negative PTB are not known and requires more research.

Informed patient consent for defaulter tracing: should we obtain it?

Active default tracing is an integral part of tuberculosis (TB) programmatic control. It can be differentiated into the tracing of defaulters (patients not seen at the clinic for > or =2 months) and 'late patients' (late for their scheduled appointments). Tracing is carried out to obtain reliable information about who has truly died, transferred out or stopped treatment, and, if possible, to persuade those who have stopped treatment to resume. This is important because, unlike routine care for non-communicable diseases, TB has the potential for transmission to other members of the community, and therefore presents the issue of the rights of the individual over the rights of the community. For this reason, default or 'late patient' tracing (defined together as default tracing in this article) has been incorporated into standard practice in most TB programmes and, in many industrialised countries, it is also a part of public health legislation. In resource-poor countries with limited access to phones or e-mails, default tracing involves active home visits. In this Unresolved Issues article, we discuss the need for patient consent within both the programmatic and the research context; we describe how this subject arose during operational research training at the Research Institute of Tuberculosis in Japan; we provide comments from individuals who are experienced and skilled at international and national TB control; and finally we offer some conclusions about the way forward. This is not an easy subject, and we welcome open debate on the issue.

HIV-related tuberculosis: how well are we doing with current control efforts?

SETTING

The top 25 human immunodeficiency virus (HIV) prevalence countries.

OBJECTIVE

To review the current status of implementation of interventions to control HIV-related tuberculosis (TB).

DESIGN

Using data on national TB and HIV programme activities from the most recent national survey results published by international public health agencies, we reviewed the status of implementation of selected key interventions to control HIV-related TB.

RESULTS

Regarding implementation of the DOTS strategy for TB control, only four of the top 25 HIV prevalence countries reported achieving the target for treatment outcomes. Nearly all countries reported low levels of national programme performance in implementing key HIV prevention and care measures.

CONCLUSIONS

The generally low performance of national TB and HIV programmes in the top 25 HIV prevalence countries is unlikely to make a significant impact on control of HIV-related TB. Controlling HIV-related tuberculosis requires increased investment in full implementation of the DOTS strategy and the key HIV prevention measures. In settings fully implementing these basic interventions, collaboration between TB and HIV programmes is necessary to scale up implementation of additional prioritised interventions to control HIV-related TB (e.g., antiretroviral therapy, intensified TB case finding and isoniazid and cotrimoxazole preventive therapies) that are of demonstrated feasibility, effectiveness and cost-effectiveness.

Seventy percent of the Mycobacterium tuberculosis isolates in Hong Kong represent the Beijing genotype

We used spoligotyping to study 500 randomly selected pretreatment Mycobacterium tuberculosis (MTB) strains isolated in Hong Kong during the 2 year period 1998-9. It was found that amongst all MTB strains studied, the 'Beijing' genotype strains were highly prevalent in our geographic area, representing about 70% of the isolates. Unlike previous observations in Vietnam, no significant associations were found either between 'Beijing' genotype strains and all other anti-tuberculosis drug resistance phenotypes, or with particular patients' age groups, except for a weak association with isoniazid susceptibility. Eighteen of these strains exhibited spoligotype patterns that were similar but not identical to the 'Beijing' specific pattern. This is the first geographical area where genetic diversity among 'Beijing' genotype of MTB strains has been observed on this scale.

Estimating treatment effects in randomized clinical trials in the presence of non-compliance

In clinical trials where patients are randomized between two treatment arms, not all patients comply with the treatment they were randomly assigned to. The reasons for (non)compliance may be associated with the outcome variable and thereby act as confounders. The standard way of analysing such trials is by the 'intention-to-treat' principle, which allows the use of permutation tests. Conclusions drawn from such tests do not depend on untested assumptions such as absence of confounding. However, this approach may yield biased estimators for the causal effects of treatments. We consider the estimation of such effects for clinical trials where non-compliers can be considered to have switched to the other trial arm. The most important example of this is the placebo-controlled clinical trial where no substantial placebo effects are anticipated. We consider the situation where the relationship between compliance, and thus treatment received, and outcome is influenced by unobserved confounders. The residual of the regression of the actual treatment indicator variable on the randomization arm indicator variable is shown to 'intercept' the effect of such confounders. Inclusion of this residual in a multivariate analysis, in conjunction with the treatment indicator variable, should thus adjust for confounding. Examples are given. In those examples, the results are similar to those obtained by more complex methods.

Estimating treatment effects in randomized clinical trials in the presence of non-compliance

In clinical trials where patients are randomized between two treatment arms, not all patients comply with the treatment they were randomly assigned to. The reasons for (non)compliance may be associated with the outcome variable and thereby act as confounders. The standard way of analysing such trials is by the 'intention-to-treat' principle, which allows the use of permutation tests. Conclusions drawn from such tests do not depend on untested assumptions such as absence of confounding. However, this approach may yield biased estimators for the causal effects of treatments. We consider the estimation of such effects for clinical trials where non-compliers can be considered to have switched to the other trial arm. The most important example of this is the placebo-controlled clinical trial where no substantial placebo effects are anticipated. We consider the situation where the relationship between compliance, and thus treatment received, and outcome is influenced by unobserved confounders. The residual of the regression of the actual treatment indicator variable on the randomization arm indicator variable is shown to 'intercept' the effect of such confounders. Inclusion of this residual in a multivariate analysis, in conjunction with the treatment indicator variable, should thus adjust for confounding. Examples are given. In those examples, the results are similar to those obtained by more complex methods.

Semi-parametric estimation of age-time specific infection incidence from serial prevalence data

Many infections cause lasting detectable immune responses, whose prevalence can be estimated from cross-sectional surveys. However, such surveys do not provide direct information on the incidence of infection. We address the issue of estimating age and time specific incidence from a series of prevalence surveys under the assumption that incidence changes exponentially with time, but make no assumption about the age specific incidence. We show that these assumptions lead to a proportional hazards model and estimate its parameters using semi-parametric maximum likelihood methods. The method is applied to tuberculin surveys in The Netherlands to explore age dependence of the risk of tuberculous infection in the presence of a strong secular decline in this risk.

A population-based study of syphilis and sexually transmitted disease syndromes in north-western Tanzania. 1. Prevalence and incidence

OBJECTIVE

To determine the prevalence of syphilis and the prevalence and incidence of self-reported STD syndromes in the population of Mwanza Region, North-Western Tanzania.

METHODS

A population-based random cluster sample survey, stratified by rural, roadside or urban residence, of 4173 individuals aged 15-54 years was performed in 1990-91. The seroprevalence of syphilis (using TPHA and RPR) and the prevalence and incidence of self-reported genital ulcer syndrome (GUS) and genital discharge syndrome (GDS) were determined.

RESULTS

Active syphilis was detected in 9% of the adult population, while 15% had serological evidence of past or current infection. Seroprevalence was significantly lower in the rural than in the roadside and urban populations, but there was little difference between men and women. Amongst men, a history of GDS was reported by 28%, and a history of GUS by 14%, with point prevalences of 2.3% and 1.3% respectively. Annual incidence among men were 6.8% for GDS and 3.6% for GUS. Women reported these conditions less frequently. There was little difference between the strata in the prevalence or incidence of reported STD syndromes.

CONCLUSION

Sexually transmitted diseases represent a major public health problem in both the rural and urban populations of Mwanza Region.

A population-based study of syphilis and sexually transmitted disease syndromes in north-western Tanzania. 2. Risk factors and health seeking behaviour

OBJECTIVE

To determine risk factors for syphilis and sexually transmitted disease (STD) syndromes, and to study health seeking behaviour among those with STD syndromes, in the population of Mwanza Region, North-Western Tanzania.

METHODS

A population-based random cluster sample survey, stratified by rural, roadside or urban residence, of 4173 individuals aged 15-54 years was performed in 1990-91. The seroprevalence of syphilis and the prevalence and incidence of self-reported genital ulcer syndrome (GUS) and genital discharge syndrome (GDS) are reported in the accompanying paper. This paper reports on risk factors for these conditions and on health seeking behaviour among those reporting them.

RESULTS

In both sexes, the risk of STDs increased with the reported number of sexual partners in the previous five years. Men who were separated, divorced or widowed were at increased risk of STDs, but this was not the case among women. Higher educational status was associated with an increased risk of urethral discharge in males but with a decreased prevalence of syphilis in females. Male circumcision was associated with an increased risk of urethral discharge but a reduced prevalence of syphilis. Nearly all men, and 90% of women, reporting symptoms of genital discharge or ulceration had sought treatment. Of these, approximately 70% of males and 60% of females had sought treatment in the official health sector.

CONCLUSIONS

Targetted health education concerning risk reduction for HIV infection and other STDs should be a high priority in this population. Improved case management of STDs in health centres and dispensaries may have a substantial impact on the incidence of these infections.

Sentinel surveillance for HIV-1 among pregnant women in a developing country: 3 years' experience and comparison with a population serosurvey

OBJECTIVES

To establish unlinked, anonymous sentinel surveillance for HIV-1 among pregnant women attending an antenatal clinic, to determine age-specific seroprevalences, to monitor trends and to compare seroprevalence with that detected by a population serosurvey. To establish the sustainability and costs of surveillance.

DESIGN

Sentinel surveillance for HIV through serial collection of unlinked, anonymous seroprevalence data from antenatal care; comparison of sentinel data with those from a population serosurvey; financial and general audit of the sentinel surveillance.

SETTING

A community antenatal clinic in a large urban centre, Mwanza Municipality, Tanzania, eastern Africa, between October 1988 and September 1991.

PATIENTS

Pregnant women attending for antenatal care.

MAIN OUTCOME MEASURE

Age-specific HIV-1 seroprevalences, trends over time, difference from age-specific population seroprevalences, sustainability and costs.

RESULTS

Overall HIV-1 seroprevalence was 11.5% (95% confidence interval, 10.5-12.4); differences in age-specific prevalences were not significant. There was no clear evidence of change in seroprevalence over the study period in any age group, although there was some indication of a rise in some age groups in 1988-1989. Sentinel surveillance among pregnant women may have significantly underestimated population HIV-1 seroprevalence for women under the age of 35 years. HIV-1 surveillance proved feasible and sustainable. Additional recurrent costs were US$1.7 per specimen for unlinked anonymous testing and US$0.57 per woman for syphilis screening.

CONCLUSIONS

HIV-1 seroprevalence did not change significantly over 3 years, probably implying a substantial incidence of HIV-1 infection. In this setting seroprevalence in pregnant women may have underestimated population seroprevalence in women aged under 35 years. With modest inputs and good organization unlinked anonymous HIV-1 sentinel surveillance of pregnant women can be introduced and sustained in an African setting. This may usefully be carried out in conjunction with syphilis screening.

Sentinel surveillance for HIV-1 infection: how representative are blood donors, outpatients with fever, anaemia, or sexually transmitted diseases, and antenatal clinic attenders in Mwanza Region, Tanzania?

OBJECTIVE

To assess the validity of extrapolation from sentinel data by comparing the HIV-1 prevalence of various sentinel groups with that of the general population in Mwanza Region, Tanzania.

METHODS

In a population survey, 4161 individuals were selected in a stratified random cluster sample. Sentinel groups (all in the age group 15-54 years) included blood donors (n = 1090); patients examined at district hospitals for the presence of malaria parasites (n = 1488), anaemia (n = 1339), or syphilis (n = 33); and antenatal clinic attenders (n = 1193). The HIV-1 serostatus of individuals selected from the population survey was tested using enzyme-linked immunosorbent assay (ELISA) and Western blot; 51% of the blood donors were tested using HIVCHEK, and all others using ELISA. HIV-1 prevalence was standardized for age, sex, and urban/non-urban location.

RESULTS

HIV-1 prevalence (standardized by age, sex, and residence) in Mwanza Region was 4.0% (3.0% in non-urban areas and 11.3% in town). The standardized HIV-1 prevalences in the sentinel groups were: blood donors, 4.5%; patients with fever, 11.6%; patients with anaemia, 8.9%; urban sexually transmitted disease patients, 27.1%; urban antenatal clinic attenders, 11.8%. The crude prevalence in blood donors was 6.0%.

CONCLUSION

Blood donors who are related to blood recipients appear to be a representative sentinel group in this region, provided that data are standardized for age, sex, and urban/non-urban location. Patients with fever and antenatal clinic attenders may reflect trends, but data from patients with fever markedly overestimate, and data from antenatal clinic attenders underestimate, population HIV-1 prevalence. Because self-selection of blood donors may become more pronounced, this comparison should be repeated later or elsewhere, should the opportunity arise.