Latent tuberculosis among pregnant mothers in a resource poor setting in Northern Tanzania: a cross-sectional study

Document Type

Article

Department

Imaging and Diagnostic Radiology (East Africa)

Abstract

It is estimated that TB infection is present in one-third of the world's population, or 2 billion people. Eight million new cases of active disease have been estimated to occur worldwide annually[1]. The prevalence of LTBI in Sub-Saharan Africa is 31%[2], while that of HIV is 5%-35% of the adult population; one-third to one-half of HIV-infected individuals are co-infected with Mycobacterium tuberculosis[1].

The incidence of tuberculosis among women in South Africa (mean age 33.4 years) increased from 154/100,000 to 413/100,000 between 1991 and 1995; 44% of this increase was attributable to HIV-1 infection [3]. Similar increases in notification in women were reported in Tanzania between 1985 and 1991 [4] in keeping with the global increase in tuberculosis.

In a South African study, TB was the third leading cause of maternal mortality, mostly in combination with HIV-infection[5]. Neonatal mortality and extreme prematurity have also increased significantly due to the problem[6]. Tanzania has not been spared.

Women between the ages of 15 and 49 years carry the greatest risk of converting from tuberculosis infection to disease[7]. It is expected that the incidence of latent tuberculosis among pregnant women would be as high as in general population, although no studies have been conducted to substantiate this fact. The rate of active TB in pregnant women ranges from 0.1% to 1.9% [8]. Furthermore, the risk of mother-to-child-transmission for active disease is 15% within 3 weeks of delivery [9].

The usefulness of the Tuberculin Skin Test (TST) in diagnosing LTBI has always been debated, especially since the introduction of more sensitive interferon gamma (IFN gamma) assays. While research has shown that pregnancy does not alter tuberculin reactivity and that this test is entirely safe and reliable for pregnant women [10], the same has not been substantiated for IFN-gamma assays. Skin testing is also cheaper and more readily available in resource poor settings.

Despite the amount of research conducted on screening for active TB there has been scanty work done on latent tuberculosis among pregnant women in developing countries. Hence the need for a study aimed at evaluating the prevalence of LTBI in pregnancy and the association between various socio-demographic/obstetric parameters and latent TB infection is evident. Chest radiography was included as part of the work up of TST positive pregnant women, especially since it is vital to rule out active TB before initiation of Isoniazid Prophylactic Therapy (IPT).

Comments

 This work was published before the author joined Aga Khan University.

Publication (Name of Journal)

BMC infectious diseases

DOI

https://doi.org/10.1186/1471-2334-10-52

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