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Epidemiology of tuberculosis in a high HIV prevalence population provided with enhanced diagnosis of symptomatic disease.

Corbett EL, Bandason T, Cheung YB, Munyati S, Godfrey-Faussett P, Hayes R, Churchyard G, Butterworth A, Mason P - PLoS Med. (2007)

Bottom Line: HIV prevalence was 19%.Most patients with prevalent culture-positive TB had subclinical disease when first detected.This may translate into effective control of TB transmission despite high TB incidence rates and a period of subclinical infectiousness in some patients.

View Article: PubMed Central - PubMed

Affiliation: London School of Hygiene and Tropical Medicine, London, United Kingdom. elc1@mweb.co.zw

ABSTRACT

Background: Directly observed treatment short course (DOTS), the global control strategy aimed at controlling tuberculosis (TB) transmission through prompt diagnosis of symptomatic smear-positive disease, has failed to prevent rising tuberculosis incidence rates in Africa brought about by the HIV epidemic. However, rising incidence does not necessarily imply failure to control tuberculosis transmission, which is primarily driven by prevalent infectious disease. We investigated the epidemiology of prevalent and incident TB in a high HIV prevalence population provided with enhanced primary health care.

Methods and findings: Twenty-two businesses in Harare, Zimbabwe, were provided with free smear- and culture-based investigation of TB symptoms through occupational clinics. Anonymised HIV tests were requested from all employees. After 2 y of follow-up for incident TB, a culture-based survey for undiagnosed prevalent TB was conducted. A total of 6,440 of 7,478 eligible employees participated. HIV prevalence was 19%. For HIV-positive and -negative participants, the incidence of culture-positive tuberculosis was 25.3 and 1.3 per 1,000 person-years, respectively (adjusted incidence rate ratio = 18.8; 95% confidence interval [CI] = 10.3 to 34.5: population attributable fraction = 78%), and point prevalence after 2 y was 5.7 and 2.6 per 1,000 population (adjusted odds ratio = 1.7; 95% CI = 0.5 to 6.8: population attributable fraction = 14%). Most patients with prevalent culture-positive TB had subclinical disease when first detected.

Conclusions: Strategies based on prompt investigation of TB symptoms, such as DOTS, may be an effective way of controlling prevalent TB in high HIV prevalence populations. This may translate into effective control of TB transmission despite high TB incidence rates and a period of subclinical infectiousness in some patients.

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Related in: MedlinePlus

Point Prevalence and Annual Incidence Rates for Smear-Positive and Culture-Positive TB, According to HIV StatusColumns are divided into smear-positive (dark portion) and smear-negative culture-positive TB (light portion).
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pmed-0040022-g002: Point Prevalence and Annual Incidence Rates for Smear-Positive and Culture-Positive TB, According to HIV StatusColumns are divided into smear-positive (dark portion) and smear-negative culture-positive TB (light portion).

Mentions: A total of 106 patients with definite or probable TB occurred during cohort follow-up, of whom 61 (58%) were smear or culture positive. An additional 11 patients were treated for TB that did not meet case definitions. Overall TB incidence was 9.9 (95% CI = 7.8 to 12.9) per 1,000 person-years follow-up for all definite and probable disease. A breakdown of incidence rates by HIV status and smear and culture category is shown in Table 2 and Figure 2. Univariate- and multivariate-adjusted incidence rate ratios (IRRs) and PAFs for all TB cases and for culture-positive TB disease are shown in Table 3.


Epidemiology of tuberculosis in a high HIV prevalence population provided with enhanced diagnosis of symptomatic disease.

Corbett EL, Bandason T, Cheung YB, Munyati S, Godfrey-Faussett P, Hayes R, Churchyard G, Butterworth A, Mason P - PLoS Med. (2007)

Point Prevalence and Annual Incidence Rates for Smear-Positive and Culture-Positive TB, According to HIV StatusColumns are divided into smear-positive (dark portion) and smear-negative culture-positive TB (light portion).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC1761052&req=5

pmed-0040022-g002: Point Prevalence and Annual Incidence Rates for Smear-Positive and Culture-Positive TB, According to HIV StatusColumns are divided into smear-positive (dark portion) and smear-negative culture-positive TB (light portion).
Mentions: A total of 106 patients with definite or probable TB occurred during cohort follow-up, of whom 61 (58%) were smear or culture positive. An additional 11 patients were treated for TB that did not meet case definitions. Overall TB incidence was 9.9 (95% CI = 7.8 to 12.9) per 1,000 person-years follow-up for all definite and probable disease. A breakdown of incidence rates by HIV status and smear and culture category is shown in Table 2 and Figure 2. Univariate- and multivariate-adjusted incidence rate ratios (IRRs) and PAFs for all TB cases and for culture-positive TB disease are shown in Table 3.

Bottom Line: HIV prevalence was 19%.Most patients with prevalent culture-positive TB had subclinical disease when first detected.This may translate into effective control of TB transmission despite high TB incidence rates and a period of subclinical infectiousness in some patients.

View Article: PubMed Central - PubMed

Affiliation: London School of Hygiene and Tropical Medicine, London, United Kingdom. elc1@mweb.co.zw

ABSTRACT

Background: Directly observed treatment short course (DOTS), the global control strategy aimed at controlling tuberculosis (TB) transmission through prompt diagnosis of symptomatic smear-positive disease, has failed to prevent rising tuberculosis incidence rates in Africa brought about by the HIV epidemic. However, rising incidence does not necessarily imply failure to control tuberculosis transmission, which is primarily driven by prevalent infectious disease. We investigated the epidemiology of prevalent and incident TB in a high HIV prevalence population provided with enhanced primary health care.

Methods and findings: Twenty-two businesses in Harare, Zimbabwe, were provided with free smear- and culture-based investigation of TB symptoms through occupational clinics. Anonymised HIV tests were requested from all employees. After 2 y of follow-up for incident TB, a culture-based survey for undiagnosed prevalent TB was conducted. A total of 6,440 of 7,478 eligible employees participated. HIV prevalence was 19%. For HIV-positive and -negative participants, the incidence of culture-positive tuberculosis was 25.3 and 1.3 per 1,000 person-years, respectively (adjusted incidence rate ratio = 18.8; 95% confidence interval [CI] = 10.3 to 34.5: population attributable fraction = 78%), and point prevalence after 2 y was 5.7 and 2.6 per 1,000 population (adjusted odds ratio = 1.7; 95% CI = 0.5 to 6.8: population attributable fraction = 14%). Most patients with prevalent culture-positive TB had subclinical disease when first detected.

Conclusions: Strategies based on prompt investigation of TB symptoms, such as DOTS, may be an effective way of controlling prevalent TB in high HIV prevalence populations. This may translate into effective control of TB transmission despite high TB incidence rates and a period of subclinical infectiousness in some patients.

Show MeSH
Related in: MedlinePlus