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The association between household socioeconomic position and prevalent tuberculosis in Zambia: a case-control study.

Boccia D, Hargreaves J, De Stavola BL, Fielding K, Schaap A, Godfrey-Faussett P, Ayles H - PLoS ONE (2011)

Bottom Line: Prevalent TB was significantly associated with lower household SEP [aOR = 6.2, 95%CI: 2.0-19.2 and aOR = 3.4, 95%CI: 1.8-7.6 respectively for low and medium household SEP compared to high].These associations were not confounded by household SEP.While the fight against HIV remains central for TB control, interventions addressing low household SEP and, especially food availability, may contribute to strengthen our control efforts.

View Article: PubMed Central - PubMed

Affiliation: Faculty of Epidemiology and Population Health, Department of Infectious Disease Epidemiology, London School of Hygiene and Tropical Medicine, London, United Kingdom. Delia.Boccia@lshtm.ac.uk

ABSTRACT

Background: Although historically tuberculosis (TB) has been associated with poverty, few analytical studies from developing countries have tried to: 1. assess the relative impact of poverty on TB after the emergence of HIV; 2. explore the causal mechanism underlying this association; and 3. estimate how many cases of TB could be prevented by improving household socioeconomic position (SEP).

Methods and findings: We undertook a case-control study nested within a population-based TB and HIV prevalence survey conducted in 2005-2006 in two Zambian communities. Cases were defined as persons (15+ years of age) culture positive for M. tuberculosis. Controls were randomly drawn from the TB-free participants enrolled in the prevalence survey. We developed a composite index of household SEP combining variables accounting for four different domains of household SEP. The analysis of the mediation pathway between household SEP and TB was driven by a pre-defined conceptual framework. Adjusted Population Attributable Fractions (aPAF) were estimated. Prevalent TB was significantly associated with lower household SEP [aOR = 6.2, 95%CI: 2.0-19.2 and aOR = 3.4, 95%CI: 1.8-7.6 respectively for low and medium household SEP compared to high]. Other risk factors for prevalent TB included having a diet poor in proteins [aOR = 3.1, 95%CI: 1.1-8.7], being HIV positive [aOR = 3.1, 95%CI: 1.7-5.8], not BCG vaccinated [aOR = 7.7, 95%CI: 2.8-20.8], and having a history of migration [aOR = 5.2, 95%CI: 2.7-10.2]. These associations were not confounded by household SEP. The association between household SEP and TB appeared to be mediated by inadequate consumption of protein food. Approximately the same proportion of cases could be attributed to this variable and HIV infection (aPAF = 42% and 36%, respectively).

Conclusions: While the fight against HIV remains central for TB control, interventions addressing low household SEP and, especially food availability, may contribute to strengthen our control efforts.

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Related in: MedlinePlus

Study design and flowchart of study participants.Grey boxes show the cases of TB that have been not included in the case-control study. *HAIN Life Science, based on acid nucleic amplification technology. † Samples were re-tested after data on the initial 106 cases and 318 controls had been already collected. ** Overall 79 cases were eventually detected in the prevalence survey. Of them only 52 were included in the present case control study. The remaining 27 were not included because identified after the fieldwork was completed. §The 54 cases excluded were classified as follows: M. intracellulare (N. 21), Non Mycobacteria Type 1 (N. 9), M. scrofulaceum (N. 3), M. asiaticum (N. 2), M. goodie (N. 1), M. gordonae (N. 1), M. parafinicum (N. 1), M. peregrinum (N. 1), M. terrae II (N. 1). The remaining 14 strains were classified as unidentified Mycobacteria species.
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pone-0020824-g001: Study design and flowchart of study participants.Grey boxes show the cases of TB that have been not included in the case-control study. *HAIN Life Science, based on acid nucleic amplification technology. † Samples were re-tested after data on the initial 106 cases and 318 controls had been already collected. ** Overall 79 cases were eventually detected in the prevalence survey. Of them only 52 were included in the present case control study. The remaining 27 were not included because identified after the fieldwork was completed. §The 54 cases excluded were classified as follows: M. intracellulare (N. 21), Non Mycobacteria Type 1 (N. 9), M. scrofulaceum (N. 3), M. asiaticum (N. 2), M. goodie (N. 1), M. gordonae (N. 1), M. parafinicum (N. 1), M. peregrinum (N. 1), M. terrae II (N. 1). The remaining 14 strains were classified as unidentified Mycobacteria species.

Mentions: Initially 106 out of the 403 cultures showing evidence of growth were identified as M. tuberculosis positive through the niacin accumulation test and/or identified by spoligotyping. Based on the study protocol, all these cases were included in the case-control study together with 318 controls (Figure 1). Two months after the completion of data collection, all the 403 cultures were re-tested with the Genotype Mycobacteria CM Assay (HAIN test. Life Science), a nucleic acid amplification-based technology known to be highly specific for M. tuberculosis [25]. Only 52 of the 106 cases initially identified were confirmed to be M. tuberculosis (Figure 1).


The association between household socioeconomic position and prevalent tuberculosis in Zambia: a case-control study.

Boccia D, Hargreaves J, De Stavola BL, Fielding K, Schaap A, Godfrey-Faussett P, Ayles H - PLoS ONE (2011)

Study design and flowchart of study participants.Grey boxes show the cases of TB that have been not included in the case-control study. *HAIN Life Science, based on acid nucleic amplification technology. † Samples were re-tested after data on the initial 106 cases and 318 controls had been already collected. ** Overall 79 cases were eventually detected in the prevalence survey. Of them only 52 were included in the present case control study. The remaining 27 were not included because identified after the fieldwork was completed. §The 54 cases excluded were classified as follows: M. intracellulare (N. 21), Non Mycobacteria Type 1 (N. 9), M. scrofulaceum (N. 3), M. asiaticum (N. 2), M. goodie (N. 1), M. gordonae (N. 1), M. parafinicum (N. 1), M. peregrinum (N. 1), M. terrae II (N. 1). The remaining 14 strains were classified as unidentified Mycobacteria species.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3117783&req=5

pone-0020824-g001: Study design and flowchart of study participants.Grey boxes show the cases of TB that have been not included in the case-control study. *HAIN Life Science, based on acid nucleic amplification technology. † Samples were re-tested after data on the initial 106 cases and 318 controls had been already collected. ** Overall 79 cases were eventually detected in the prevalence survey. Of them only 52 were included in the present case control study. The remaining 27 were not included because identified after the fieldwork was completed. §The 54 cases excluded were classified as follows: M. intracellulare (N. 21), Non Mycobacteria Type 1 (N. 9), M. scrofulaceum (N. 3), M. asiaticum (N. 2), M. goodie (N. 1), M. gordonae (N. 1), M. parafinicum (N. 1), M. peregrinum (N. 1), M. terrae II (N. 1). The remaining 14 strains were classified as unidentified Mycobacteria species.
Mentions: Initially 106 out of the 403 cultures showing evidence of growth were identified as M. tuberculosis positive through the niacin accumulation test and/or identified by spoligotyping. Based on the study protocol, all these cases were included in the case-control study together with 318 controls (Figure 1). Two months after the completion of data collection, all the 403 cultures were re-tested with the Genotype Mycobacteria CM Assay (HAIN test. Life Science), a nucleic acid amplification-based technology known to be highly specific for M. tuberculosis [25]. Only 52 of the 106 cases initially identified were confirmed to be M. tuberculosis (Figure 1).

Bottom Line: Prevalent TB was significantly associated with lower household SEP [aOR = 6.2, 95%CI: 2.0-19.2 and aOR = 3.4, 95%CI: 1.8-7.6 respectively for low and medium household SEP compared to high].These associations were not confounded by household SEP.While the fight against HIV remains central for TB control, interventions addressing low household SEP and, especially food availability, may contribute to strengthen our control efforts.

View Article: PubMed Central - PubMed

Affiliation: Faculty of Epidemiology and Population Health, Department of Infectious Disease Epidemiology, London School of Hygiene and Tropical Medicine, London, United Kingdom. Delia.Boccia@lshtm.ac.uk

ABSTRACT

Background: Although historically tuberculosis (TB) has been associated with poverty, few analytical studies from developing countries have tried to: 1. assess the relative impact of poverty on TB after the emergence of HIV; 2. explore the causal mechanism underlying this association; and 3. estimate how many cases of TB could be prevented by improving household socioeconomic position (SEP).

Methods and findings: We undertook a case-control study nested within a population-based TB and HIV prevalence survey conducted in 2005-2006 in two Zambian communities. Cases were defined as persons (15+ years of age) culture positive for M. tuberculosis. Controls were randomly drawn from the TB-free participants enrolled in the prevalence survey. We developed a composite index of household SEP combining variables accounting for four different domains of household SEP. The analysis of the mediation pathway between household SEP and TB was driven by a pre-defined conceptual framework. Adjusted Population Attributable Fractions (aPAF) were estimated. Prevalent TB was significantly associated with lower household SEP [aOR = 6.2, 95%CI: 2.0-19.2 and aOR = 3.4, 95%CI: 1.8-7.6 respectively for low and medium household SEP compared to high]. Other risk factors for prevalent TB included having a diet poor in proteins [aOR = 3.1, 95%CI: 1.1-8.7], being HIV positive [aOR = 3.1, 95%CI: 1.7-5.8], not BCG vaccinated [aOR = 7.7, 95%CI: 2.8-20.8], and having a history of migration [aOR = 5.2, 95%CI: 2.7-10.2]. These associations were not confounded by household SEP. The association between household SEP and TB appeared to be mediated by inadequate consumption of protein food. Approximately the same proportion of cases could be attributed to this variable and HIV infection (aPAF = 42% and 36%, respectively).

Conclusions: While the fight against HIV remains central for TB control, interventions addressing low household SEP and, especially food availability, may contribute to strengthen our control efforts.

Show MeSH
Related in: MedlinePlus