Pooled sputum testing by Xpert? MTB/RIF Ultra for active tuberculosis case finding among high-risk groups in a low-incidence area: a prospective study

Background: Early detection and treatment of tuberculosis (TB) are of great importance to stop its spread. However, optimising the active case findingstrategy is critical to improving its feasibility in regions where TB is epidemic. Method: The different pooled ratios between TB-positive and TB-negative sputum specimens were evaluated and a pooling ratio of 5:1 was used for the active case finding screening by Xpert MTB/RIF Ultra among high-risk groups in Beijing. Results: The sensitivity of pooling ratio at 5:1 was 97.5% (39/40). Between October 2022 and March 2023, among 17,681 participants, 1729 met the active case finding criteria and were screened by 350 5:1 sputum pools by Xpert MTB/RIF Ultra. Four pools (1.1%) tested positive and were further confirmed as definite active TB cases. In our study population with high TB incidence (231/100,000), the cost for detection of individual patients was reduced by 77.4% at a 5:1 pooling ratio. Conclusions: pooled sputum testing at a suitable ratio using Xpert MTB/RIF Ultra provides a rapid, efficient, and cost-effective method for active TB case finding among high-risk groups in a low-incidence area.