Radford: Now is the Time for Heightened Focus on the TB Threat

While most people living in the United States might think tuberculosis (TB) is a disease that no longer affects this country, in reality, between nine and 14 million Americans are infected with the bacteria that cause TB.

Consider the number of people you come in contact with every day – at the office, home, airports, trains, buses, restaurants, schools, hospitals, and shopping centers – it takes just one person with TB disease in any of these settings to pose a risk to all those around them.

A contagious disease, TB is spread through the air when a person with TB disease of the lungs or throat coughs, sneezes, speaks, or sings, which may cause people in close proximity to become infected. TB usually attacks the lungs, but it often affects other organs, and if not treated properly, it can be fatal. Around one in every 10 TB-infected people will, without treatment, go on to develop potentially deadly TB disease.

So why is TB still prevalent in the U.S.?

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Doctor holding test tube

A key reason has to do with the very things that are supposed to help protect us from TB: the Bacille Calmette-Guérin (BCG) vaccine and the main method of TB testing traditionally used, the 110+-year-old tuberculin skin test (TST).

The BCG vaccine is widely-adopted globally and its use engrained in TB control policies around the world.

However, it is recognized by many around the world that the BCG vaccine confounds the TST and leads to false-positive test results.

This means that for the many foreign-born Americans who have been BCG-vaccinated, the usual method of TB testing will often indicate that they are positive for TB infection. With migration to the US (approximately one million per year, many from countries where TB is endemic), TB rates have been steadily growing in foreign-born individuals - in 2009 immigrants were nearly 11 times more likely than U.S.-born citizens to have TB.

Certain communities are also at higher risk: people with autoimmune conditions and those taking immunosuppressive therapies, the elderly, the homeless, and corrections facility inmates. As a consequence of frequent contact with high-risk individuals, doctors, nurses, and staff at hospitals and other group facilities are all at significant risk of TB.

The major challenge for the U.S. is to modernize TB control.

The first hurdle will be for the nation to adopt new strategies for TB control and diagnosis. The U.S. Centers for Disease Control and Prevention (CDC) istaking steps to pave the way for change.

In a landmark Public Health release issued last week, CDC is now championing the use of modern TB testing strategies. The CDC advises that IGRAs, simple blood tests known as interferon-gamma release assays, are now preferred over the TST for diagnosing TB infection in many groups of individuals. Further, the CDC in conjunction with the U.S. Department of Health and Human Services (Division of Global Migration and Quarantine) recently published new instructions for immigrant TB testing, which allow the blood tests to be used instead of the TST in certain immigration populations.

Using these tests for immigration TB screening will prevent the large number of false-positive TST results in BCG-vaccinated immigrants and stem unnecessary (and expensive) evaluation and treatment.

The distinct advantages of these blood tests, such as QuantiFERON®-TB Gold (QFT®),are greater accuracy over TST and not being confounded by BCG vaccination.

These blood tests frequently show that fewer than a third of those previously thought TST-positive truly have TB and can provide more valuable information for physicians to diagnose TB infection. Economic studies show that, when staff time and evaluation of TST false-positives are included in cost comparisons, QFT reduces testing program costs by seven percent while providing superior medical outcomes.

Public health and TB control programs across the U.S. are also successfully beginning to implement change.

At the forefront is the San Francisco Department of Public Health’s TB Control Health Program. The program’s switch from TST to QFT resulted in a more than 60 percent decline in the number of people testing positive for TB last year and, thus, a reduced number of follow-up visit costs. Despite this lower number of positive results, no cases of TB have been reported as missed in more than 45,000 people screened for TB in San Francisco since QFT was adopted.

Switching for healthcare worker screening alone saved the program $101,648 in the course of one year.

The CDC’s announcement is a great move in the direction of tackling how TB is tested. Success will eventually be measured by local government and other groups’ adoption of these guidelines. Although TB is not on most Americans’ radar, it remains a significant public health threat in the U.S., with still much more to be done.

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Dr Tony Radford is the founding CEO of Cellestis Limited, a biotechnology company formed in 2000 in Melbourne, Australia, and listed on the Australian Stock Exchange (ASX). Dr. Radford was a senior member of Australia’s Commonwealth Scientific and Industrial Research Organization (CSIRO) team that invented the patented QuantiFERON® technology, which is used world-wide for testing for diseases such as tuberculosis. Cellestis develops and manufactures the QuantiFERON®-TB Gold (QFT) test, a breakthrough blood test for the detection and control of tuberculosis.