Sensitivity, Specificity, and Safety of a Novel ESAT6-CFP10 Skin Test for Tuberculosis Infection in China: 2 Randomized, Self-Controlled, Parallel-Group Phase 2b Trials

Background: Diagnostics to identify tuberculosis infection are limited. We aimed to assess the diagnostic accuracy and safety of ESAT6-CFP10 (EC) skin test for tuberculosis infection in Chinese adults.

Methods: We conducted 2 randomized, parallel-group clinical trials in healthy participants and tuberculosis patients. All participants were tested with the T-SPOT.TB test, then received an EC skin test and tuberculin skin test (TST). The diameter of skin indurations and/or redness at injection sites were measured at different time periods. A bacillus Calmette Guerin (BCG) model was established to assess the diagnosis of tuberculosis infection using an EC skin test.

Results: In total, 777 healthy participants and 96 tuberculosis patients were allocated to receive EC skin test at 1.0 μg/0.1 mL or 0.5 μg/0.1 mL. The area under the curve was 0.95 (95% confidence interval [CI], .91-.97) for the EC skin test at 1.0 μg/0.1 mL at 24-72 hours. Compared with the T-SPOT.TB test, the EC skin test demonstrated similar sensitivity (87.5, 95% CI, 77.8-97.2 vs 86.5, 95% CI, 79.5-93.4) and specificity (98.9, 95% CI, 96.0-99.9 vs 96.1, 95% CI, 93.5-97.8). Among BCG vaccinated participants, the EC skin test had high consistency with the T-SPOT.TB test (96.3, 95% CI, 92.0-100.0). No serious adverse events related to the EC skin test were observed.

Conclusions: The EC skin test demonstrated both high specificity and sensitivity at a dose of 1.0 μg/0.1 mL, comparable to the T-SPOT.TB test. The diagnostic accuracy of the EC skin test was not impacted by BCG vaccination.

Clinical trials registration: NCT02389322 and NCT02336542.