Do women with tuberculosis have a lower likelihood of getting diagnosed?: Prevalence and case detection of sputum smear positive pulmonary TB, a population-based study from Vietnam

doi:10.1016/j.jclinepi.2002.11.001

Journal of Clinical Epidemiology

Volume 57, Issue 4, April 2004, Pages 398-402

https://doi.org/10.1016/j.jclinepi.2002.11.001 Get rights and content

Abstract

Objective

The aim was to estimate the gender-specific prevalence of tuberculosis (TB) through screening. A further aim was to calculate case detection within the Vietnamese National TB program.

Study design and setting

A population-based survey of 35,832 adults was performed within an existing sociodemographic longitudinal study in Bavi district, northern Vietnam. Cases were identified by a screening question about prolonged cough and further diagnosed with sputum examination and a chest X-ray.

Results

The estimated prevalence of pulmonary TB among men was 90/100,000 (95% CI 45–135/100,000) and among women 110/100,000 (95% CI 63–157/100,000). Case detection in the district was estimated to 39% (95% CI 20–76%) among men and 12% (95% CI 6–26%) among women.

Conclusion

TB prevalence was similar among men and women. Case detection among men and women was significantly lower than the reported national case detection of 80%, and there was a significant underdetection of female cases. These findings warrant actions, and emphasize the need to perform similar studies in different contexts.

Introduction

In 1998, 3.6 million cases of tuberculosis (TB) were reported to the World Health Organisation (WHO). The notified cases represent only about 45% of the estimated number of TB cases world-wide [1]. The TB control strategy recommended by the WHO is based on self-referral to health services together with other measures to ensure adequate diagnosing and compliance to treatment. According to the WHO to influence the incidence of TB, at least 70% of all smear-positive cases should be detected and 85% of these successfully treated [1]. So far, the strategy has not succeeded in creating major changes in the course of the epidemic, and TB is still one of the most important causes of mortality in low-income countries, despite the effective and relatively cheap chemotherapy [1], [2]. Individuals with TB without adequate access to the health care system are not reported in global statistics and run the greatest risk of failing to get effective treatment [1]. Apart from causing individual morbidity, inadequately treated TB cases create a large public health risk by enhancing disease transmission and increasing the risk of drug resistance [3].

About two-thirds of notified TB cases world-wide during 1998 were men and one-third women [1]. This difference in notification rates has been explained both by sociocultural factors, that is, men have more social contacts and thus run a greater risk of exposure to contagious cases, and by immunologic differences between men and women [4]. In both cases TB infection, potentially leading to TB disease, is considered more common among men. These hypotheses are now questioned and an undernotification of female TB cases is currently discussed [5], [6], [7].

Population-based research studies of TB prevalence or incidence using screening are very rare. A study from Nepal in 1980 exists, and shows an under notification of female cases when self-referral is compared to screening [8].

During 1999, in Vietnam 54,873 new smear positive pulmonary TB cases were reported to the Vietnamese National Tuberculosis Programme (NTP). Sixty-six percent of these cases were men and 33% women [9]. The Vietnamese NTP reports 80% case detection and a 92% cure rate, which makes Vietnam one of only two high-burden countries that reach the WHO set targets for TB control [1].

In this study we aimed at estimating the “true” TB prevalence through screening of men and women in a population-based survey. A further aim was to calculate case detection rate ratios of the National TB Programme in Bavi district, Vietnam.

Section snippets

Methods

The study was carried out during April–June 2000, in the Bavi District, Ha Tay province in north-west Vietnam, where a population-based sociodemographic survey (hereafter called FilaBavi) has been set up. The population of Bavi district is 241,812. In the study base, 67 clusters out of 352 were selected by randomized stratified cluster sampling. Eleven thousand four hundres seventy-three households with 49,710 individuals were thus included in the Filabavi (Fig. 1). This study included all

Smear-positive pulmonary TB cases identified

In the study population of 35,832 adults 259 (1.5%) men and 300 (1.6%) women (potential TB cases) reported a cough with a duration of 3 weeks or longer at the time of interview.

Among the potential cases we detected 25 individuals with a sputum smear showing presence of acid fast bacilli. All these TB cases supplied three sputum samples. Chest x-rays for 22 of the cases were considered suggestive of TB; two men and one woman did not go for a chest x-ray (see Fig. 1). Twenty-four of the cases

Discussion

To our knowledge, this is the first population-based study using a screening instrument to identify TB cases in Vietnam, and one of only very few research studies carried out world-wide [11]. The study provides a point of departure for a discussion of case detection within the WHO recommended model for national TB programs in general, and specifically a possible undernotification of female TB cases.

The estimated “true” prevalence of smear-positive pulmonary TB in our study population was found

Acknowledgements

This study was carried out within the sociodemographic survey project in the Bavi district, Vietnam (FilaBavi), and thanks are due to the individuals living in the district and taking part in the studies. Financial support was given by Sida/SAREC.

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Original ArticlesDo women with tuberculosis have a lower likelihood of getting diagnosed?: Prevalence and case detection of sputum smear positive pulmonary TB, a population-based study from Vietnam

Abstract

Objective

Study design and setting

Results

Conclusion

Introduction

Section snippets

Methods

Smear-positive pulmonary TB cases identified

Discussion

Acknowledgements

Health Policy

Lancet

Health Policy

J Clin Epidemiol

Hlth Policy

World Health Organization global tuberculosis control WHO Report

World Health report, 1999: Making a difference

Adult tuberculosis in the 21st century: pathogenesis, clinical features and management

Curr Opin Pulmon Med

Original Articles
Do women with tuberculosis have a lower likelihood of getting diagnosed?: Prevalence and case detection of sputum smear positive pulmonary TB, a population-based study from Vietnam

Adult tuberculosis in the 21^st century: pathogenesis, clinical features and management