C-Tb skin test to diagnose Mycobacterium tuberculosis infection in children and HIVinfected adults : a phase 3 trial

Aggerbeck, Henrik ; Ruhwald, Morten ; Hoff, Soren T. ; Borregaard, Bettine ; Hellstrom, Elizabeth ; Malahleha, Mookho ; Siebert, Mirna ; Gani, Mashra ; Seopela, Vincent ; Diacon, Andreas ; Lourens, Madeleine ; Andersen, Peter ; Dheda, Keertan (2018)

CITATION: Aggerbeck, H., et al. 2018. C-Tb skin test to diagnose Mycobacterium tuberculosis infection in children and HIVinfected adults : a phase 3 trial. PLoS ONE, 13(9):e0204554, doi:10.1371/journal.pone.0204554.

The original publication is available at https://journals.plos.org/plosone/


Background C-Tb, an ESAT-6/CFP-10-based skin test, has similar sensitivity for active TB compared to tuberculin skin test (TST) and QuantiFERON-TB-Gold-In-Tube (QFT). However, data are limited in children and HIV-infected persons. Methods Asymptomatic South African contacts <5 years (n = 87; HIV-uninfected), or symptomatic individuals of all ages presenting to clinics with suspected TB (n = 1003; 30% HIV-infected) were recruited from eight South African centres. C-Tb and TST were allocated to either forearm double blinded. Samples for QFT were collected in parallel, and test-positivity rates were compared. Results In participants with microbiologically confirmed TB (n = 75; 45% HIV-infected) sensitivity of C-Tb, TST and QFT were similar (72% versus 75% versus 73%; p>0.5). All 3 tests had similar positivity rates in HIV-infected participants with active TB, however, positivity rates were reduced when CD4 counts were <100 cells/μL. In participants where active TB was excluded (n = 920), C-Tb (41%), TST (43%), and QFT (44%) also had similar test-positivity rates. Among asymptomatic contacts aged below five, 32% (28/87) tested positive with C-Tb and 32% (28/87) with TST (concordance 89%). Overall, C-Tb and TST showed a similar safety profile. Conclusion C-Tb was safe and showed similar test-positivity rates, compared to TST and QFT, in children and HIV-infected persons with active or latent M. tuberculosis infection. These data inform the utility of C-Tb in clinical practice.

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