Showing posts with label TST. Show all posts
Showing posts with label TST. Show all posts

Tuesday, 12 April 2011

TUBERCULOSIS: Community-based cross-sectional survey of latent tuberculosis infection in Afar pastoralists, Ethiopia, using QuantiFERON-TB Gold In-Tube and tuberculin skin test


Author: Mengistu LegesseGobena AmeniGezahegne MamoGirmay MedhinGunnar BjuneFekadu Abebe

Credits/Source: BMC Infectious Diseases 2011, 11:89

There is little information concerning community-based prevalence of latent tuberculosis infection (LTBI) using T-cell based interferon-gamma (IFN-gamma) release assays (IGRAs), particularly in TB endemic settings. In this study, the prevalence of LTBI in the Afar pastoral community was assessed using QuantiFERON-TB Gold In-Tube (QFTGIT) and tuberculin skin tests (TST).

Methods:
A community-based cross-sectional survey of LTBI involving 652 apparently healthy adult pastoralists was undertaken in the pastoral community of Amibara District of the Afar Region between April and June 2010.

Results:
The prevalence of LTBI was estimated as 63.7% (363/570) using QFTGIT at the cut-off point recommended by the manufacturer ([greater than or equal to] 0.35 IU/ml IFN-gamma), while it was 74.9% (427/570) using a cut-off point [greater than or equal to] 0.1 IU/ml IFN-gamma.
The QFTGIT-based prevalence of LTBI was not significantly associated with the gender or age of the study participants. However, the prevalence of LTBI was 31.2% (183/587) using TST at a cut-off point [greater than or equal to] 10 mm of skin indurations, and it was higher in males than females (36.8% vs.
23.5%, X2 =11.76; p <0.001). There was poor agreement between the results of the tests (k= 0.098, 95% CI, 0.08 - 0.13).
However, there was a positive trend between QFTGIT and TST positivity (X2 = 96.76, P<0.001). Furthermore, individuals with skin indurations [greater than or equal to] 10 mm were 13.6 times more likely to have positive results using QFTGIT than individuals with skin indurations of 0 mm (adjusted OR = 13.6; 95%CI, 7.5 to 24.7, p <0.001).

Conclusions:
There is currently no agreed gold standard for diagnosis of LTBI.
However, the higher prevalence of LTBI detected using QFTGIT rather than TST suggests that QFTGIT could be used for epidemiological studies concerning LTBI at the community level, even in a population unreactive to TST. Further studies of adults and children will be required to assess the effects of factors such as malnutrition, non-tuberculosis mycobacterial infections, HIV and parasitic infections on the performance of QFTGIT.
http://7thspace.com/headlines/378533/community_based_cross_sectional_survey_of_latent_tuberculosis_infection_in_afar_pastoralists_ethiopia_using_quantiferon_tb_gold_in_tube_and_tuberculin_skin_test_.htm

Saturday, 18 December 2010

TUBERCULOSIS: Tuberculosis: threatening Australia’s borders

Tony Radford, CEO of Cellestis. (Cellestis offers a solution to curb influx of tuberculosis brought in by immigrants and refugees.)

Tuberculosis (TB) is regarded by many as a disease of the past, but as a recent tuberculosis outbreak in Australian’s customs offices shows, there is a case for modernising testing for TB in developed nations, and Melbourne-based company Cellestis offers a way to do so.
The recent scare involving six Australian customs officials who appear to have contracted a latent tuberculosis infection has called into question the current protection and testing measures. The episode also highlights that while TB infection rates in Australia are relatively low – around 1000 new cases are reported per year – we remain exposed to real risks.
Additionally, a study released last year, following a review of Victorian health department data from 1998 to 2007, found there was an increase in the number of people who were diagnosed with MDR-TB, a mutant strain that is resistant to two of the most effective antibiotics used to treat TB. Even more dangerously, resistant strains of TB exist and are becoming more common around the world, and it can’t be ignored that this disease kills one person every 17 seconds worldwide.
This recent scare focuses our attention on TB in immigrants, and rightly so. In Australia, the chances of contracting TB from an Australian-born person are very low. The infection is mostly imported – because we make no effort to stop anything but the most developed cases from entering the country.
We allow people to enter the community carrying TB infection, possibly drug-resistant, in a manner that we would never consider allowable for any animal crossing our borders. Not even considering the rising number of boats arriving on our shores – 173 illegal boats since 2008 – even legal immigrants aren’t receiving the necessary TB testing to prevent a further outbreak of the highly infectious respiratory disease.
Tools which far more accurately detect TB infection and indicate who will develop TB are now available, rendering the old-fashioned mind-set that finding TB and treating it is too hard is simply that – old and out of date. This, coupled with the rising number of immigrants coming in from countries with a high rate of TB (Asia accounts for 55 per cent and Africa accounts for 30 per cent of all TB cases), are good reasons for Australian authorities to reconsider TB control. Demands need to be made for an overhaul and upgrade in the country’s testing and protection against the infectious disease.
Australia needs to step up its action plan against TB to match the global standard of disease management. The world-wide strategy is being led by the US, which this year released new guidelines recommending that the modern IGRAs (simple blood tests known as interferon-gamma release assays, like Cellestis’ QuantiFERON) are used to test for TB, and similarly endorsed their use in screening immigrants.
Other countries that have realised they need to take a tougher stance against TB include Ireland, which recently experienced an outbreak of TB in a primary school. With a usually low rate of TB – around 480 cases a year – the outbreak has caused the country to urgently review its testing and protection methods for the disease to prevent a reoccurrence. The clearly acknowledged fact is that some countries with low rates took their eye off the ball, and now, with rising TB rates they are paying the price. Australia is in a unique position with its geographical separation, and needs to develop and enact modernised TB control guidelines in immigration to prevent a similar situation occurring on our shores.
This is to the benefit of all. Latent TB carriers will be detected and will be treated before progressing to TB disease, it is clearly to their benefit. It is not expensive to diagnose or treat latent TB infection – it is expensive to wait and treat TB disease. The current immigrant testing protocol simply does not allow for testing and treating TB infection, but relies only on chest X-ray, which can only and inefficiently detect advanced disease, not latent infection.
Why is it so? X-ray can largely avoid the embarrassment of an immigrant immediately infecting others straight after arrival, but does little to stop importing the disease. But until Australians invented interferon testing, first for cattle TB, the only method to find TB infection was the tuberculin skin test, the TST or Mantoux test.
The TST is over 100 years old, extremely subjective to measure, and very frequently produces false positives. Such an unreliable test causes undue stress, and adds extra and unnecessary pressure on the health system and economy. Doctors are often uncomfortable prescribing treatment based on such a test, and this ‘do nothing’ mindset has permeated immigration testing. Customs workers are exposed on a daily basis to possible infection, and deserve better.
Cellestis’ QuanitFERON test (QFT) is scientifically proven to be six times more accurate than the TST – that is, six times fewer people need to be treated to stop the same amount of TB – and has demonstrated that the new test offered economic advantages of time saving through the elimination of producing false positives as with the TST tests.
It is clear that despite having the possibility of virtually eliminating TB in this country, saving money while showing a shining light to the world that a country can achieve this goal with a comparative modicum of effort and thought, Australia is lagging behind other nations. We have little control over TB infection coming into the country, and little to no guideline on interferon testing for TB infection.
The federal government in fact facilitates and subsidises the import and use of the TST reagents from the USA – where the US Centers for Disease Control and Prevention recommends use of QFT as beneficial in BCG (Bacillus Calmette-GuĂ©rin) vaccinated people, which is in fact common in immigrants and those most likely to have TB infection – to compete with this Australian product.
Cellestis’ has a declared an emphatic strategy to make latent TB diagnosis and treatment the paradigm in all countries. It makes solid health and economic sense. Current world TB-control strategies have had only limited success, and it’s clear that killing latent infection before it becomes a serious disease stops further spread – and if a test with high predictive capacity for future TB such as QuantiFERON is used, this will be achieved very economically.
The World Health Organisation has published reports clearly showing that only treatment of latent TB can make any significant impact on TB disease. The outcome of effective TB control is not only to save existing carriers but to cut the chain of transmission before the situation worsens.
The Stop TB Partnership, which gathered in early October to discuss a global plan to tackle TB, predicted that up to ten million people will die of the respiratory disease in the next five years. There is little cause to think it will go away in the world, and a lot of reason to worry about antibiotic resistant strains. Although only 1000 cases are reported in Australia each year, this number is set to rise if our borders are not protected with sufficient testing, and disease protection, for immigrants.

http://www.lifescientist.com.au/article/367368/opinion_tuberculosis_threatening_australia_borders/

Saturday, 10 July 2010

TUBERCULOSIS: New CDC Guidelines Prefer Use of Blood Tests, Including QuantiFERON®-TB, to Diagnose Tuberculosis Infection in Certain Populations

TB Remains a Major Public Health Threat in Both Developing and Developed Countries
June 24 -- Today the United States (U.S.) Centers for Disease Control and Prevention (CDC) issued new and important guidelines on the detection of Mycobacterium tuberculosis infections, the causative agent of tuberculosis (TB). In these landmark guidelines, CDC advises that Interferon Gamma Release Assay (IGRA) blood tests are now preferred over the 100+-year-old tuberculin skin test (TST) for diagnosing TB infection in certain populations, including people who typically do not return for the necessary reading of TST results, and those who have received Bacille Calmette-Guerin (BCG) as a vaccine or for cancer therapy. Typically the TST or IGRAs, such as QuantiFERON®-TB Gold (QFT), manufactured by Cellestis Limited, should be used as aids to diagnose infection with M. tuberculosis.
"In the U.S., up to 14 million Americans may be infected with TB bacteria and are at risk of developing full-blown, highly contagious TB. With these sobering numbers, complacency about TB's public health impact is not an option," said Antonino Catanzaro, M.D., professor of medicine, University of California San Diego, and Non-Executive Independent Director, Cellestis Limited. "These guidelines encapsulate the enormous body of clinical evidence on the performance of the QFT test and reflect the significant benefits this test is bringing to TB control worldwide."
The CDC report, "Updated Guidelines for Using Interferon Gamma Release Assays to Detect Mycobacterium tuberculosis Infection — United States, 2010" along with a companion implementation guide, appears in the June 25, 2010, Volume 59, No. RR-5 issue of the CDC's Morbidity & Mortality Weekly Report (MMWR). TST's drawbacks – which include a higher risk for false positives, especially in people who have been BCG-vaccinated; irritating TB-extract that must be injected under the skin; and the need for a second doctor's visit – were evaluated by the CDC and factored into their recommendations.
Approximately one person dies of TB every 17 seconds. Each infected person represents a potential yet preventable future outbreak. Convenient and trustworthy testing for TB infection is vital in order to efficiently identify the appropriate persons for treatment and thereby prevent its spread.
The populations specified by CDC in these guidelines, represent a majority of those being screened for TB infection. "With a specificity of more than 99 percent, QFT virtually eliminates false positive results and is simple to administer," said Tony Radford, chief executive officer, Cellestis Limited. "With more than 400 peer-reviewed, published clinical studies, QFT is a modern, scientifically–validated solution for reliable diagnosis of TB infection, and offers significant economic and public health advantages."
Specific highlights from the recommendations with regards to IGRAs include:
IGRAs are preferred over the TST for testing persons who have received BCG (as a vaccine or for cancer therapy).
IGRAs are preferred over the TST for diagnosing TB infection for persons from groups that historically have low rates of returning to have TSTs read.
IGRAs may be used in place of (not in addition to) TST in all situations in which CDC recommends testing, and is considered acceptable medical and public health practice.
IGRAs may be used in place of TST (without preference) to test recent contacts of persons with infectious tuberculosis.
IGRAs may be used in place of TST (without preference) for periodic screening to address occupational exposure to TB.
A TST is preferred for testing children aged <5 years. Use of an IGRA in conjunction with TST has been advocated by some experts to increase diagnostic sensitivity in this age group. Recommendations regarding use of IGRAs in children have also been published by the American Academy of Pediatrics.
About Tuberculosis
Tuberculosis (TB) is a contagious disease caused by a bacterium called Mycobacterium tuberculosis. TB bacteria usually attack the lungs, but can affect any part of the body such as the kidney, spine, and brain. If not treated properly, TB can be fatal. TB bacteria is spread through the air when a person with TB disease of the lungs or throat coughs, sneezes, speaks, or sings, which may lead people in close proximity to become infected.
According to the World Health Organization, about one person dies of TB every 17 seconds, causing nearly 2 million deaths annually. TB continues to be a contagious scourge in developing countries, and with the world shrinking rapidly due to global migration, it is a major public health threat in developed nations as well, including the United States. Each infected person represents a potential yet preventable future outbreak. Convenient and trustworthy testing for TB infection is necessary in order to quickly identify the appropriate persons for treatment and thereby prevent its spread.
About QuantiFERON®-TB Gold (QFT)
QuantiFERON®-TB Gold (QFT) is a simple blood test that accurately identifies people infected with Mycobacterium tuberculosis, the causative agent of Tuberculosis (TB). As a modern alternative to the 110 year old Tuberculin Skin Test (TST), also known as the Mantoux, QFT offers unmatched specificity, high sensitivity and simplicity. QFT enables focused TB therapy by providing clinicians with an accurate, reliable and convenient TB diagnostic tool. QFT is unaffected by previous BCG vaccination and most other environmental mycobacteria. Unlike the TST, it requires only one patient visit, is a controlled laboratory test and provides an objective, reproducible result that is unaffected by subjective interpretation. Results can be available within 24 hours.
QFT is available for use in all clinical settings in which TST is commonly used. Examples include contact tracing, regular employee testing, for example for health care workers, as well as screening programs for prisoners and immigrants. QFT's application in the screening of immunosuppressed patients prior to anti-TNF-alpha therapy initiation and in patients with HIV, cancer or organ transplants offers distinct advantages over the TST.
QFT® is sold directly in the U.S. by Cellestis Inc. and through Quest Diagnostics, Inc. and other commercial laboratories. In Europe QFT is provided by Cellestis GmbH (Germany); and in Australia/New Zealand by Cellestis International Pty. Ltd. (Australia). QFT is also available through Cellestis Commercial Partners in Japan, Europe, the Middle East, Africa, South America and Asia.
About Cellestis Limited
Cellestis Limited, a listed Australian biotechnology company founded in 2000 in Melbourne, Australia, develops and manufactures the QuantiFERON-TB Gold In-Tube (QFT) test, a breakthrough blood test for the detection and control of tuberculosis. The QuantiFERON technology is a patented method for detecting cell mediated immune (CMI) responses of T-cell lymphocytes using whole blood samples. In comparison to existing methods of measuring CMI, this unique technology provides accuracy and sensitivity along with major savings in operator time, labor and reagents. Using its patented QuantiFERON technology, Cellestis develops diagnostics tests that measure immune function for diseases with an unmet medical need.
Cellestis is proud to be exploring opportunities to enhance the global effort to eliminate TB. Cellestis is an industry partner of FIND (the Foundation for Innovative New Diagnostics) and the Stop-TB Partnership.
For more information, please visit
www.cellestis.com.
http://www.prnewswire.com/news-releases/new-cdc-guidelines-prefer-use-of-blood-tests-including-quantiferon-tb-to-diagnose-tuberculosis-infection-in-certain-populations-97100554.html