A new test for tuberculosis (TB) developed by Oxford Immunotec Ltd “is set to supersede the skin test”, according to Ajit Lalvani (BBC News), author of a new study published in The Lancet. Peter Wrighton-Smith, CEO of Oxford Immunotec, said that the new test “will revolutionise TB control” by improving the detection of individuals with latent TB (ISIS).

TB causes more deaths per year than any other infectious disease and the number of cases is on the increase. In Britain, the number of reported cases in 2001 was up 6% on the previous year. According to the World Health Organisation, TB is “a global health emergency”, being the biggest killer of women aged 15–44 (BBC News).

Unlike the skin-prick test (given to 600,000 schoolchildren in the United Kingdom every year), which uses a crude extract of dead bacteria to induce an inflammatory reaction, the new test uses an ELISPOT technique to look for TB-specific T cells in the blood. Results are available overnight and do not require a follow-up visit. The test is less likely to give false positives than the skin-prick test, which includes proteins that are used in the BCG vaccine and is therefore confounded by TB vaccination. The test also works well in individuals with weak immune systems, such as children, the elderly and those with AIDS. As the test can monitor how the number of specific T cells changes with time, it might also be used to monitor treatment efficacy. Although the test is more expensive than the skin prick, it should save money in the long term by eliminating the unnecessary treatment of false positives. As Lalvani noted, “The old skin test is not as cheap as it first seems” (Reuters Health).