Accuracy and safety of C-TST for tuberculosis infection: A clinical trial in Brazil.

Authors

Marcela Bhering, Carla Conceição, Martha Oliveira, Ana Paula Razal Dalvi, Marcelo Cordeiro-Santos, Adriana Rezende Moreira, Anna Cristina Calçado Carvalho, Aline Lopes, Rogerio Rufino, Luciana Rodrigues, Eliene Mesquita, Sergian Vianna Cardozo, Sumire Sakabe, Fernanda Mattos, Pedro Almeida da Silva, Anete Trajman, Afrânio Kritski

Published in

Pulmonology. Volume 32. Issue 1. Pages 2704303. Epub Jul 17, 2026.

Abstract

Tuberculosis infection (TBI) diagnosis in BCG-vaccinated, high-burden settings remains challenging.
We aimed to assess the sensitivity, specificity, and safety of the C-tuberculin skin test (C-TST), compared with PPD RT-23, for tuberculosis infection in BCG-vaccinated adults.
Randomised, double-blind clinical trial in Brazil. Adults with pulmonary tuberculosis (PTB) and asymptomatic controls without known TB exposure or prior TB/TPT underwent C-TST, PPD RT-23, and QuantiFERON-TB Gold Plus (QFT-Plus). Skin tests were read by two strategies: (a) induration only or (b) induration or erythema, at a ≥5-mm cut-off. Sensitivity was assessed in PTB; specificity for C-TST and PPD RT-23 was estimated against QFT-Plus. Adverse events were monitored.
Among 446 participants (141 PTB; 305 controls), at the 5-mm cut-off, C-TST showed lower sensitivity but higher specificity than PPD RT-23. With strategy (a) and (b), C-TST sensitivity was 0.67 and 0.68, specificity was 0.92 and 0.9, compared to 0.74 sensitivity and 0.78 specificity for PPD RT-23. Adverse events were more frequent in PTB: 12.1% (C-TST) and 6.4% (PPD RT-23); none were serious.
In BCG‑vaccinated adults, C-TST showed a trade-off of higher specificity and lower sensitivity than PPD RT-23 at the 5-mm cut-off; and a favourable safety profile. Adding erythema to readings did not improve accuracy, suggesting that C-TST may be a useful alternative for programmatic TBI screening in high-burden settings.
Trial registry number RBR-7tn2ysw (https://ensaiosclinicos.gov.br/ registered on 25 January 2021).

PMID:
42467493
Bibliographic data and abstract were imported from PubMed on 18 Jul 2026.

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