April 4, 2003
The study, "Comparison of T-cell-based Assay with Tuberculin Skin Test for Diagnosis of Mycobacterium tuberculosis Infection in a School Tuberculosis Outbreak," is published in the Lancet (2003;361(9364):1168-1173) and indicates that the new tests detected latent infections more accurately than the standard skin-prick test used for a century.
The tuberculin skin-prick test is the cornerstone of TB control in developed countries, but it has many drawbacks. It involves injecting a substance under the skin on the arm and a technician reading the resulting bump a few days later. The test can give false positive readings in people who have had the BCG TB vaccine because antibodies are made in both cases.
The new test, developed by scientists at Oxford University in England, is a blood test using a different substance to stimulate a reaction. Instead of looking for antibodies, it detects the activation of immune system T-cells.
Dr. Mark Perkins, a TB specialist at the World Health Organization, said about 95 percent of TB cases occur in the developing world, where a new diagnostic test for active TB is crucial because the current technology detects less than one-third of cases.
04.03.03; Emma Ross