Tuberculosis blood test gains EU approval

During this period, the number of TB cases in London doubled and it has been suggested that the capital is on the brink of an epidemic. Paul Sommerfeld, Chairperson of TB Alert said: ‘The importance of having access to accurate and reliable diagnosis cannot be overstated. Accurate testing is vital for effective disease control, especially with the threat of multi-drug resistant TB and the recent increase in incidence of the disease hanging over us.’

Up to now, a century-old skin test (the oldest diagnostic test still in use today) has been used, but this can produce both false-positive and false-negative results and previous BCG vaccination makes it inconsistent, according to a report from the firm Oxford Immunotec, the international clinical diagnostics company headquartered near Oxford, UK. ‘It is also inconvenient, taking 3-7 days before it can be read, and it can cause painful blistering and scarring of the skin,’ the firm added.

Now a new blood test has been approved for use in Europe. Named T SPOT-TB, and made Oxford Immunotec, this promises to replace the old TB skin test. Dr Ajit Lalvani of Oxford University, who led the development of this test over the past decade, said: ‘The tools we use to diagnose TB are 50-100 years old; this disease has been neglected for decades. I am pleased that we have finally brought the benefits of modern scientific research to the front-line to fight this age-old disease. In contrast to the crude and inaccurate skin test, the new blood test is fast, accurate and convenient. It is a 100-year upgrade for diagnosing TB and I believe it will significantly improve the way we manage tuberculosis.’

The SPOT test works in a unique way, the firm pointed out. ‘Whereas conventional diagnostic tests rely on detecting antibodies induced by an infection, such antibodies are not generated by TB infection. However, TB infection induces a strong response by immune cells in the blood called T-cells. It is these T-cells, in a small blood sample, that are detected by T SPOT-TB, which literally counts them as spots on a test plate.

The T SPOT-TB test has been tested in 16 clinical studies, involving over 4,000 patients in 11 different countries, in both the developed and developing world. 99.9% specificity was shown in healthy unexposed controls, in five separate studies of low-risk subjects. Sensitivity of the test has been shown to be over 96%.

SPOT will be used to screen people who have been in contact with a TB sufferer, so that, if infected, they could be identified and treated long before they actually develop the disease and infect others. ‘Crucially, it is the first test that reliably detects infection in people with weak immune systems, including new-born babies, people with HIV and transplant patients - precisely the people who are most vulnerable to developing full-blown TB,’ the firm added.

T SPOT-TB is Oxford Immunotec’s first product, which is based on its patented T SPOT technology, a novel platform that opens up new ways of diagnosing and monitoring infections by providing a simple and extremely accurate method of studying a person’s cellular immune response to an infection. T-SPOT technology can be applied to diagnose and monitor any major disease driven by a T-cell response, the firm pointed out.

TB - the disease and its treatment
The TB bacteria may infect most a third of the world’s population, and an estimated eight million people develop the active disease annually.
TB is passed from person to person through the air, but a person exposed to TB does not necessarily develop the disease. Some people are able to clear it from the system through their natural immune response, but most only control it and do not clear it completely, so it remains dormant in their systems. This latent infection can reactivate at any time, to cause the active disease.
TB is usually curable with effective antibiotic treatment. Typically a long course of a combination of four antibiotics is recommended for initial treatment of the active disease. If caught in its latent state, only one drug is usually needed to manage the disease.
Due to poor compliance to therapy over the long period required to completely cure TB and because there have been few new drugs to treat TB over the last 30 years, there has been a substantial increase in the number of strains of TB resistant to current treatments.
The rise and spread of multi-drug resistant (MDR) TB is a cause of great concern.

TB charity
TB Alert, registered in 1998 and launched in London’s Houses of Parliament on World TB Day in  1999, was set up by people who believe there should be a greater response to the resurgent threat of TB - already declared a global emergency by the World Health Organisation (WHO) in 1993. TB Alert is the first TB-specific charity in Britain since the 1960s, when earlier organisations, assuming too soon that the disease had been vanquished, faded away or shifted to other interests. TB Alert aims to:
• Raise awareness of TB as a global threat and as a disease resurgent in Britain
• Advocate for greater global spending on TB
• Support TB control programmes overseas, focusing on increasing access to treatment especially for poor and marginalised groups
• Complement the work of the NHS in the UK, supporting public and patient education and information

01.07.2004

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