An evaluation of symptom and chest radiographic screening in tuberculosis prevalence surveys.

SETTING: A tuberculosis (TB) prevalence survey was performed in 2002 in two urban communities in Cape Town, South Africa. The population was 36,334 in 2001, and the TB notification rate was 341 per 100,000 population for new smear-positive TB in 2002. OBJECTIVE: To evaluate the relative contributions of symptom and chest radiographic (CXR) screening in the detection of subjects with smear- and/or culture-positive TB in prevalence surveys. DESIGN: Information on symptoms, CXR abnormalities, sputum smear and culture was gathered from a random cluster sample of 1170 adults (aged > or = 15 years). Smear and/or culture-positive TB was used as the gold standard. RESULTS: Of 1170 adults, 29 had bacteriologically positive TB (smear- and/or culture-positive). The presence of any abnormalities on CXR had the highest sensitivity for detecting subjects with bacteriologically positive TB (0.97, 95%CI 0.90-1.00). Specificity for any abnormalities on CXR was 0.67 (95%CI 0.64-0.70). The specificity of any of five TB-related symptoms was 0.68 (95%CI 0.65-0.71). Individual symptoms had low sensitivities, ranging from 0.10 for fever to 0.54 for cough of > or = 2 weeks. CONCLUSION: In this TB prevalence survey, CXR screening, but not symptom screening, was a sensitive alternative to sputum examination of all participants.

Association between smoking and tuberculosis infection: a population survey in a high tuberculosis incidence area.

BACKGROUND: Associations between smoking and tuberculosis disease including death from tuberculosis have been reported, but there are few reports on the influence of smoking on the risk of developing Mycobacterium tuberculosis infection. The aim of this study was to determine the association between smoking and M tuberculosis infection. METHODS: In a cross sectional population survey, data on smoking and tuberculin skin test (TST) results of 2401 adults aged > or =15 years were compared. RESULTS: A total of 1832 (76%) subjects had a positive TST (> or = 10 mm induration). Of 1309 current smokers or ex-smokers, 1070 (82%) had a positive TST. This was significantly higher than for never smokers (unadjusted OR 1.99, 95% confidence interval (CI) 1.62 to 2.45). A positive relationship with pack-years was observed, with those smoking more than 15 pack-years having the highest risk (adjusted OR 1.90, 95% CI 1.28 to 2.81). CONCLUSION: Smoking may increase the risk of M tuberculosis infection.

Incidence of acute lymphoblastic leukaemia in white and coloured children in the Western Cape.

UNLABELLED: Objectives. To record the age-specific incidence rate (ASIR) for diagnosed acute lymphoblastic leukaemia (ALL) in coloured and white children aged 0 - 12 years in the Western Cape (WC). DESIGN: A retrospective population-based study using the 1991 population census to calculate the mean annual childhood population and the ASIR for ALL in the 0 - 4, 5 - 9 and 10 - 12-year age groups in rural and Cape Town metropolitan areas for the period 1983 - 1999. Odds ratios were calculated using EpiInfo 2000. SETTING: Registry records of the paediatric cancer units at Tygerberg and Red Cross War Memorial Children's hospitals where all children with ALL in the WC were initially treated. SUBJECTS: All white and coloured children aged 0 - 12 years diagnosed as having ALL from 1983 - 1999. OUTCOME MEASURES: The ASIR by age and ethnic group in rural and metropolitan patients in the WC. RESULTS: The estimated annual childhood population in 1991 was 709 151 with 80.4% coloured and 19.6% white children, of whom 60% were resident in the Cape Town metropolitan area and 40% in the rural area of the WC. Of 246 children with ALL diagnosed in the period 1983 - 1999, 144 were male and 102 female. The ASIR in coloured children aged 0 - 4 years was 17.1/10(6) in the rural and 30.5/10(6) in the metropolitan area, compared with 55.7/10(6) and 56.2/10(6) respectively in white children. In the 5 - 9-year age group the ASIR in coloured children was 10.0/10(6) in the rural and 16.6/10(6) in the metropolitan area compared with 27.6/10(6) and 26.7/10(6) respectively in white children. The 10 - 12-year age group had comparable incidence rates in both populations and geographical areas. Only one case occurred within a 20 km radius of the Koeberg nuclear reactor. CONCLUSIONS: White children have an ASIR for ALL comparable to rates of diagnosis in the USA, while only half as many coloured children aged 0 - 9 years were diagnosed in both the rural and metropolitan areas. This contrast may indicate significant underdiagnosis of ALL in coloured children over the period in question. The change in health policy since 1994, which has improved access to primary health care, may improve the rate of diagnosis among coloured and black children.

Tuberculosis transmission patterns in a high-incidence area: a spatial analysis.

SETTING: In the Cape Town suburbs of Ravensmead and Uitsig, tuberculosis has reached epidemic levels, with notifications of 1340/100,000 in 1996. These suburbs are characterised by overcrowding, high unemployment and poverty. It is traditionally believed that tuberculosis transmission takes place mainly in households after close contact with an infectious person. Studies have recently linked tuberculosis transmission to locations outside the household, and have associated these places with a particular high-risk lifestyle. Anthropological studies in some suburbs of Cape Town, in which a very high number of local drinking places (shebeens) were identified (17 per km2), have suggested that social drinking is part of such a lifestyle. OBJECTIVE: To investigate various risk factors and places of transmission of tuberculosis using a geographical information system (GIS). RESULTS AND CONCLUSION: The 1128 bacteriologically-proven cases of tuberculosis studied over the period 1993-1998 were investigated using spatial epidemiological techniques of exploratory disease mapping. Point pattern analysis and spatial statistics indicated clustering of cases in the areas of high incidence. Significant associations of tuberculosis notifications were found with unemployment, overcrowding and number of shebeens per enumerator sub-district. High tuberculosis notifications with unemployment and its associated poverty emerged as the strongest association.

Historic and recent events contribute to the disease dynamics of Beijing-like Mycobacterium tuberculosis isolates in a high incidence region.

SETTING: A retrospective study in an urban setting with a high tuberculosis incidence. OBJECTIVE: To study the molecular epidemiology and disease dynamics of a prevalent Mycobacterium tuberculosis strain family, F29, a subset of the Beijing strains. DESIGN: Multi-locus DNA fingerprinting and genomic analysis was used to characterise F29 isolates. Demographic and molecular epidemiologic data were correlated with those of other isolates from the setting. The geographic locations of five F29 strain clusters were plotted using a geographic information system (GIS) and an index for geographic distribution was calculated. Their cumulative temporal occurrence was also plotted. RESULTS: The genomic similarity of F29 to the Beijing-strains was confirmed. A high degree of clustering predicted high disease transmission. Spatial distribution was mostly widespread except for one cluster. Smaller foci of transmission were observed. The temporal spread showed ongoing transmission. CONCLUSION: F29 belongs to the Beijing strain group. The prevalence and high degree of strain clustering, with limited geographic clustering, indicates that F29 strains are endemic in the study community. However, recent epidemiologic events also contributed to the disease spread. The combination of molecular epidemiologic, spatial and temporal data has enhanced our understanding of the disease dynamics of Beijing strains in our study community.