Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

A new more effective tuberculosis screening test for HIV victims

06.03.2008
World Health Organization (WHO) figures show that each year an estimated 9 million new cases of tuberculosis (TB) arise in the world.

The growth of this disease remains particularly strong in Africa owing to a high proportion of HIV patients (nearly 13% compared with less than 1% in Asian countries for example). This region of the world is experiencing accelerating advance of a deadly combination of AIDS and TB, developed because the virus weakens the immune system of TB-infected individuals.

A person infected by HIV who is also contaminated with Koch’s bacillus bears a greater risk of developing active TB than a non HIV-infected individual. Latent TB infection diagnosis has for several decades been founded on a positive response to the tuberculin skin test (TST). However, TST’s reliability is limited in highly TB-endemic geographical settings because the presence in the environment of mycobacteria similar to that which causes TB plus the BCG vaccination people receive in early infancy can skew the results.

Moreover, in HIV-carrying patients, the sensitivity of the test is drastically reduced owing to their inability to develop an allergic reaction, the very basis of the skin test. TB is a strong contributing factor to HIV mortality, therefore it is of crucial importance to be able to diagnosis latent infection early in order to adopt an appropriate treatment and prevent the development of the full disease.

The development of new IGRA3 tests is based on in vitro measurement of T-cells secretion of interferon-? when challenged with antigens specific to Mycobacterium tuberculosis, the bacterium causing tuberculosis. Such assays now provide a means of getting round the drawbacks of the tuberculin skin test (TST). Yet, although these new screening methods are more effective than TST in a situation of low TB endemicity, their validity in populations subject to high risk of latent TB infection still has to be clearly established.

Results recently published of an investigation conducted in Senegal, coordinated by IRD in conjunction with other scientific institutions,1 yield important information on the comparative efficiency of the immunological method and the standard TST. The research team set up two cohorts of patients living in the Dakar area: the first one made up of HIV-infected individuals but with no detected TB; the second consisting of TB patients and people from the treatment centre who had been in contact with them during a given period.

For the first cohort, 285 adults newly infected by HIV and showing no clinical or radiological sign of TB were selected at the Fann National University Hospital Centre (Dakar) between 2003 and 2004. An ELISPOT test and a TST were performed for each patient at the beginning of the study. The TST indicated that 21% (53/247) of them had a TB infection at the moment of the test. However, this proportion reached 51% (125/247) with the ELISPOT test. It appears therefore that the latter is more sensitive than the TST whatever the stage of development of the disease. Nevertheless the ability to respond to the ELISPOT test decreases with the decrease in CD4 lymphocyte count, which appears to indicate the limits of this type of test in severely immunosuppressed individuals, as advanced-stage HIV infected patients can be.

In parallel, a cohort of 243 TB patients was followed up for 2 years. The objective this time was to determine the ability of the ELISPOT test to predict, among people living in contact with these individuals, those who run the greatest risk of developing the disease. Between January 2004 and March 2005, 3072 contacts were identified for the whole set of TB patients. Preliminary results showed the sensitivity of the two tests to be comparable with this cohort, although ELISPOT is doted with a better specificity since it is not influenced by recent BCG vaccination.

The data gathered from the studies must now be analysed in greater detail in order to determine if the new tests based on measurement of the immune response to M. tuberculosis-specific antigens can serve as a reliable diagnostic method for TB infection in geographical areas where the disease is endemic and BCG coverage is strong. Such investigations should also found out if in the future these tests could be used as markers of the development of the disease within a given population.

Grégory Fléchet - DIC

Grégory Fléchet | alfa
Further information:
http://www.ird.fr/us/actualites/fiches/2008/fas287.pdf

More articles from Health and Medicine:

nachricht Organ-on-a-chip mimics heart's biomechanical properties
23.02.2017 | Vanderbilt University

nachricht Researchers identify cause of hereditary skeletal muscle disorder
22.02.2017 | Klinikum der Universität München

All articles from Health and Medicine >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Breakthrough with a chain of gold atoms

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

Im Focus: DNA repair: a new letter in the cell alphabet

Results reveal how discoveries may be hidden in scientific “blind spots”

Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...

Im Focus: Dresdner scientists print tomorrow’s world

The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.

The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...

Im Focus: Mimicking nature's cellular architectures via 3-D printing

Research offers new level of control over the structure of 3-D printed materials

Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...

Im Focus: Three Magnetic States for Each Hole

Nanometer-scale magnetic perforated grids could create new possibilities for computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".

Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Booth and panel discussion – The Lindau Nobel Laureate Meetings at the AAAS 2017 Annual Meeting

13.02.2017 | Event News

Complex Loading versus Hidden Reserves

10.02.2017 | Event News

International Conference on Crystal Growth in Freiburg

09.02.2017 | Event News

 
Latest News

From rocks in Colorado, evidence of a 'chaotic solar system'

23.02.2017 | Physics and Astronomy

'Quartz' crystals at the Earth's core power its magnetic field

23.02.2017 | Earth Sciences

Antimicrobial substances identified in Komodo dragon blood

23.02.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>