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 Biofilm discovery suggests new way to prevent dangerous infections
23.05.2017 | University of Texas at Austin

nachricht Another reason to exercise: Burning bone fat -- a key to better bone health
19.05.2017 | University of North Carolina Health Care

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: A quantum walk of photons

Physicists from the University of Würzburg are capable of generating identical looking single light particles at the push of a button. Two new studies now demonstrate the potential this method holds.

The quantum computer has fuelled the imagination of scientists for decades: It is based on fundamentally different phenomena than a conventional computer....

Im Focus: Turmoil in sluggish electrons’ existence

An international team of physicists has monitored the scattering behaviour of electrons in a non-conducting material in real-time. Their insights could be beneficial for radiotherapy.

We can refer to electrons in non-conducting materials as ‘sluggish’. Typically, they remain fixed in a location, deep inside an atomic composite. It is hence...

Im Focus: Wafer-thin Magnetic Materials Developed for Future Quantum Technologies

Two-dimensional magnetic structures are regarded as a promising material for new types of data storage, since the magnetic properties of individual molecular building blocks can be investigated and modified. For the first time, researchers have now produced a wafer-thin ferrimagnet, in which molecules with different magnetic centers arrange themselves on a gold surface to form a checkerboard pattern. Scientists at the Swiss Nanoscience Institute at the University of Basel and the Paul Scherrer Institute published their findings in the journal Nature Communications.

Ferrimagnets are composed of two centers which are magnetized at different strengths and point in opposing directions. Two-dimensional, quasi-flat ferrimagnets...

Im Focus: World's thinnest hologram paves path to new 3-D world

Nano-hologram paves way for integration of 3-D holography into everyday electronics

An Australian-Chinese research team has created the world's thinnest hologram, paving the way towards the integration of 3D holography into everyday...

Im Focus: Using graphene to create quantum bits

In the race to produce a quantum computer, a number of projects are seeking a way to create quantum bits -- or qubits -- that are stable, meaning they are not much affected by changes in their environment. This normally needs highly nonlinear non-dissipative elements capable of functioning at very low temperatures.

In pursuit of this goal, researchers at EPFL's Laboratory of Photonics and Quantum Measurements LPQM (STI/SB), have investigated a nonlinear graphene-based...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Marine Conservation: IASS Contributes to UN Ocean Conference in New York on 5-9 June

24.05.2017 | Event News

AWK Aachen Machine Tool Colloquium 2017: Internet of Production for Agile Enterprises

23.05.2017 | Event News

Dortmund MST Conference presents Individualized Healthcare Solutions with micro and nanotechnology

22.05.2017 | Event News

 
Latest News

Physicists discover mechanism behind granular capillary effect

24.05.2017 | Physics and Astronomy

Measured for the first time: Direction of light waves changed by quantum effect

24.05.2017 | Physics and Astronomy

Marine Conservation: IASS Contributes to UN Ocean Conference in New York on 5-9 June

24.05.2017 | Event News

VideoLinks
B2B-VideoLinks
More VideoLinks >>>