TY - JOUR T1 - Diagnostic accuracy of the novel C-Tb skin test for LTBI, results from two phase III trials JF - European Respiratory Journal JO - Eur Respir J DO - 10.1183/13993003.congress-2016.OA3037 VL - 48 IS - suppl 60 SP - OA3037 AU - Morten Ruhwald AU - Joan Cayla AU - Henrik Aggerbaek AU - Keertan Dheda AU - Peter L. Andersen Y1 - 2016/09/01 UR - http://erj.ersjournals.com/content/48/suppl_60/OA3037.abstract N2 - Rationale C-Tb is a novel specific skin test, based on ESAT-6 and CFP10, combining the field friendliness of Tuberculin (TST), with the specificity of IGRA.Methods The TESEC-06 trial included 979 participants from 13 sites in Spain with risk of M.tb infection. The TESEC-05 trial included 1090 participants with symptoms of TB and 100 endemic controls both from South Africa. C-Tb and TST were done blinded. Skin indurations were read 2-3 days later, ≥5mm was considered positive for TST and C-Tb. IGRA testing (QFT) was done prior to skin testing.Results Test specificity was assessed in 212 presumed unexposed controls. C-Tb had comparable specificity to QFT (both 97%). Previous BCG vaccination had a strong negative impact on TST specificity, 62% (67/108) compared to 95% in unvaccinated (p<0.001). Sensitivity of C-Tb and QFT was comparable in patients with TB 77% (235/307) vs 81% (250/307) (p=0.08).In contacts, there was a strong trend in increasing C-Tb test positivity with M.tb exposure, at-par with QFT. The impact of age and HIV infection on C-Tb reactivity was assessed in 1090 suspects of TB disease, C-Tb as well as TST and QFT was negatively impacted by age<2y and CD4 <100.Discussion C-Tb has comparable diagnostic performance to QFT, and addresses the problem of false positive TST results in BCG vaccinated. The C-Tb test could allow for improved target treatment of M.tuberculosis infected in resource restraint settings. ER -