Diagnosing TB, One Test at a Time

By Alberto Gutierrez, Ph.D.

For centuries tuberculosis, or simply TB as it is commonly referred to today, was fatal for millions of people living around the world. Most people infected with the bacterium Mycobacterium tuberculosis, the most common cause of tuberculosis, show no symptoms of TB. However, approximately 10 percent of those infected, such as those with weakened immune systems, will develop active TB disease. With active disease, the bacteria generally attack a person’s lungs, but can also attack other parts of the body such as the kidney, spine, and brain. Tuberculosis is spread through the air when a person with active TB disease of the lungs or throat coughs, sneezes, or speaks. People who are close by may breathe in the bacteria and become infected.

The most common symptoms associated with active TB disease include: a persistent cough lasting for three weeks or longer, chest pain, weakness or fatigue, weight loss, night sweats, and fever. People infected with TB who also have weakened immune systems have a much higher risk for not containing the bacteria and developing active disease, which can be fatal if left untreated. Today, the disease is also a leading killer of people with HIV worldwide. 

Alberto Gutierrez, Ph.D.

Past and present experiences have taught us that the proper diagnosis of TB is critically important in order to prevent the spread of TB.

For our part, the agency recently announced plans to lower the risk classification for nucleic acid-based TB tests used to detect the presence of copies of tuberculosis bacterium genetic materials (RNA or DNA) in a mucus (sputum) sample obtained from the person. This type of test allows for the timely identification of TB disease.

These tests can diagnose active TB infections in one to two hours and when used in conjunction with other clinical tests, can result in earlier treatment, improved patient outcomes, and interrupt further spread of TB.

The FDA currently considers nucleic acid-based TB tests high-risk (Class III) medical devices that require the agency to conduct a rigorous review to verify the product’s safety and effectiveness before they are used with patients. Under the new proposal, these tests would be considered moderate-risk (Class II) devices.

While the pathway to market would be considerably shorter, given the importance of these tests, the agency has still provided guidance to the developers of these tests that identifies the risks associated with false positive and false negative test results, the risks to health care workers handling specimens, and makes recommendations on how to mitigate these risks.  

It is the FDA’s hope that this more streamlined and flexible regulatory approach will ultimately encourage the development of new and more innovative TB diagnostics that will aid us in our fight to prevent the spread and hopefully one day, eliminate the presence of TB.

Alberto Gutierrez, Ph.D., is the Director of the Office of In Vitro Diagnostic Device Evaluation and Safety in FDA’s Center for Devices and Radiological Health