TUBERCULOSIS: Portugal: Screening for tuberculosis and prediction of disease in healthcare workers

Author: Jose Torres CostaRui SilvaFelix RingshausenAlbert Nienhaus
Credits/Source: Journal of Occupational Medicine and Toxicology 2011, 6:19

Introduction
Results of systematic screening of healthcare workers (HCWs) for tuberculosis (TB) with the tuberculin skin test (TST) and interferon-gamma release assays (IGRA) in a Portuguese hospital from 2007 to 2010 are reported.

Methods: All HCWs are offered screening for TB. Screening is repeated depending on risk assessment.
TST and QuantiFERON Gold In-Tube (QFT) are used simultaneously. X-ray is performed when TST is >10 mm, IGRA is positive or typical symptoms exist.

Results: The cohort comprises 2,889 HCWs. TST and IGRA were positive in 29.5%, TST-positive but IGRA-negative results were apparent in 43.4%. Active TB was diagnosed in twelve HCWs - eight cases were detected during screening and four cases were predicted by IGRA as well as by TST.
However, the progression rate in IGRA-positive was higher than in TST-positive HCWs (0.4% vs. 0.2%, p-value 0.06).

Conclusions: The TB burden in this cohort was high (129.8 per 100,000 HCWs).
However, the progression to active TB after a positive TST or positive IGRA was considerably lower than that reported in literature for close contacts in low-incidence countries. This might indicate that old LTBI prevails in these HCWs.
http://7thspace.com/headlines/385581/screening_for_tuberculosis_and_prediction_of_disease_in_portuguese_healthcare_workers.html

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

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