Abstract
INTRODUCTION: Newer skin tests, including the ESAT6-CFP10 (EC) skin test, were recommended for diagnosing Mycobacterium tuberculosis (M. tb) infection. However, no data exist assessing the diagnostic performance of the EC skin test among foreign students with different skin tones. METHODS: A cohort study at Nanjing Medical University screened incoming foreign freshmen. The EC skin test was used to assess for M. tb infection, and results were read at 24, 48, 72, and 96-hours post-administration. RESULTS: Among 96 participants, M. tb infection rates at 24, 48, 72, and 96-hours post-injection were 3.13%, 7.29%, 13.54%, and 9.38%, respectively. While infection rates were lower among individuals with darker skin tones, the difference was not statistically significant (P=0.186), and variations were consistent across different measurement times. Trajectory analysis revealed 5.3% in the continuous-increasing group, 86.5% in the low-stable group, and 5.2% in the elevated-decreasing group. Notably, participants in the elevated-decreasing group had lighter skin tones, with trajectory patterns consistent across different skin colors. DISCUSSION: The EC skin test is safe, and redness diameter is a more reliable indicator than induration. Results should be collected within 48 to 72 hours, with verification at 72 hours crucial if initial results are negative. Importantly, skin color does not affect EC skin test outcomes.