A new policy recommendation released on 20 July by the World Health Organization (WHO) warns against the use of serological (blood) tests to diagnose active tuberculosis (TB). Serological tests measure antibodies to TB in serum and are different to QuantiFERON, which measures responses of white blood cells to TB specific proteins.
Active tuberculosis occurs when the TB organism has overcome the body's immune defences and proliferates to cause clinical symptoms. According to WHO, TB takes one life every 17 seconds globally. People with active disease often shed live TB bacteria and infect others. A person who is infected with the bacteria that causes TB, but who shows no symptoms and is not sick with the disease, is said to have latent TB infection (LTBI). People with LTBI are at risk of developing active TB, particularly if their immune system becomes depressed.
QFT is intended as an aid to the diagnosis of TB infection, both active and latent, and does not discriminate between the two conditions. Cellestis Limited, manufacturer of QuantiFERON®-TB Gold (QFT), has become aware that some media reports have caused confusion around the WHO announcement. The press release from WHO clearly notes that it refers to serological (antibody-based) blood tests for active TB, and their comments do not apply to Interferon-Gamma Release Assays (IGRAs) for diagnosing latent TB. This has been confirmed by direct correspondence by WHO to Cellestis.
"QuantiFERON-TB was developed in response to the poor quality of previous tests such as those referred by WHO. We thoroughly agree with the comments of WHO regarding serological tests for active TB," said Dr Jim Rothel, Chief Scientific Officer of Cellestis. "It is imperative to recognize that TB is still one of the world's deadliest diseases. We are confident that QFT has the ability to help reduce the future healthcare burden of TB, and potentially help to lower healthcare costs related to TB and reduce the risk of epidemics."
QFT is well-regarded by the public health and infectious disease communities, and evidence of its clinical effectiveness and utility in tuberculosis management has been supported over the years in more than 600 peer-reviewed studies published in prestigious medical journals throughout the world.