"A new skin test for tuberculosis infection has proven safe easy to administer and accurate in two Phase III clinical trials according to research presented at the ATS  International Conference. The test known as CTb combines the field friendliness of the PPDbased tuberculin skin test with the high specificity of interferon gamma release assays or IGRAs said lead researcher Morten Ruhwald MD PhD head of human immunology at Statens Serum Institut in Denmark which developed the test. The new test measures the bodys immune response to two TB antigens EAST and CFP. The test is administered like a tuberculin skin test TST and results are interpreted by measuring the size of the skin induration two or three days later.  The TST is the most commonly used test to detect TB infection with about  million tests worldwide each year according to the World Health Organization. The test is easy to administer but produces too many false positives to achieve the WHOs goal of reducing TB deaths by  percent and new cases by  percent by  Dr. Ruhwald said. Introduced a decade ago IGRAs have high specificity producing few false positives but require blood samples and complicated lab work which has limited their widespread use. There is also a dramatic price difference between the two diagnostic tests. According to Dr. Ruhwald a TST costs about  an IGRA is  to  times more expensive depending on setting.  In the first clinical trial Dr. Ruhwald and colleagues conducted a doubleblinded study of CTb in  participants enrolled at  clinical trial sites in Spain. Participants all adults ranged in TB status from presumed uninfected through intermediate and high risk of latent TB to active disease.  Researchers found  Both CTb and the IGRA had a specificity of  percent.  CTb was highly concordant to IGRA in  percent of study participants.  The specificity of CTb unlike the TST was not impacted by the BCG vaccine the partially effective vaccine that many residents in the developing world receive. TST specificity in this group was only  percent.  The sensitivity of CTb was comparable to the IGRA in confirmed TB cases  percent vs.  percent indicating similar abilities to detect infection.  In the second doubleblinded trial researchers were primarily concerned with testing how accurate CTb was in HIVpositive patients and in young childrenpopulations in which the accuracy of the TST and the IGRA is known to be compromised. The study conducted in South Africa enrolled  participants including  patients with HIV and  children as young as  days.  Researchers found  Among participants with HIV the ability of all three tests to detect TB infection was diminished though the CTb appeared more robust in HIVinfected participants with low CD T cell counts.   Among children under  CTb was comparable with the other two tests in identifying those infected.  Dr. Ruhwald said another advantage of CTb is that the measurement of infection a mm or larger induration is universal across patients with different risk factors including HIV infection. With TST the size of the induration is often adjusted to increase its accuracy in measuring infection in different patient populations. Regulatory approval for CTb is currently being sought and Statens Serum Institute is actively seeking a commercial partner for marketing of CTb. The cost of a CTb test is to be determined however it is expected to be significantly less than an IGRA.  Abstract   Diagnostic Accuracy of the Novel CTb Skin Test for Latent M.tuberculosis Infection Results from Two Phase III Clinical Trials  M. Ruhwald J.A. Cayla H. Aggerbaek K. Dheda P. Andersen  Statens Serum Institut  CopenhagenDK Public Health Agency of Barcelona  BarcelonaES UCT Lung Institute Lung Infection  Immunity Unit  Cape TownZA Rationale  Renewed emphasis on the detection and preventive treatment of M. tuberculosisinfected individuals at risk is required to reach the goals of the WHO post global tuberculosis strategy.  Statens Serum Institut has developed a novel specific skin test CTb based on the antigens ESAT and CFP. CTb combines the field friendliness of the PPDbased Tuberculin Skin Test TST with the high specificity of the interferon gamma release assays IGRA.  This presentation outlines the results from two recently completed phase III trials TESEC and . The results have not previously been published or presented. Methods  The TESEC trial included  participants from  clinical trial sites in Catalonia Galicia and Basque Country Spain with various risk profiles of M.tuberculosis infection. The TESEC trial included  participants with symptoms of TB and  endemic controls from Cape Town South Africa.  In both trials CTb and TST were administered in a doubleblinded fashion to one or the other forearm. Skin indurations were read  to  days later. A reading mm was considered positive for the TST and CTb cut off preset in phase II. Blood for IGRA testing Quantiferon QFTGIT was drawn prior to skin testing. Results  The safety profile of CTb was acceptable and not different from TST. Test specificity was assessed in  presumed unexposed Spanish controls. Here CTb had comparable specificity to QFTGIT both  p. and there was no impact of BCG vaccination. By contrast previous BCG vaccination subverted TST specificity   in BCG vaccinated compared to   in BCG unvaccinated persons p.. Sensitivity of CTb and QFTGIT was comparable in patients with confirmed TB   vs   p.. In contacts mirroring the findings with QFTGIT there was a strong trend in increasing CTb test positivity with M. tuberculosis exposure figure . The impact of age and HIV infection on CTb TST and QFT reactivity was assessed in  individuals with symptoms suspect of TB disease analysis is ongoing and will be included in the presentation. Discussion  These phase III trial results demonstrate that CTb is safe has comparable diagnostic performance to QFTGIT and addresses the problem of false positive TST results in BCG vaccinated persons.  The fieldfriendliness and high specificity offered by the CTb test could allow for improved targeted treatment of M. tuberculosisinfected persons in also in resourceconstrained settings where IGRAs are too complicated to implement."