Pooled sputum testing for the detection of pulmonary tuberculosis by Xpert(R) MTB/RIF Ultra: a multi-site cross-sectional diagnostic evaluation study in Bangladesh

BackgroundXpert(R) MTB/RIF Ultra (Xpert Ultra) is a WHO recommended molecular test for rapid tuberculosis (TB) detection, but cartridge cost limits large-scale use of Xpert Ultra in high TB burden, resource-constrained countries. This study assessed the diagnostic performance of Xpert Ultra on pooled sputum for detection of pulmonary TB (PTB)in Bangladesh. MethodsBetween July 2024 and February 2025, adults with presumptive PTB were prospectively enrolled from primary and secondary healthcare facilities through facility-based case finding, and from urban slum communities through community-based case finding. Participants provided two sputum samples, one for individual and pooled Xpert Ultra testing, and another for culture. Pooled and individual Xpert Ultra results were compared to the microbiological reference standard of culture. Cost analysis was performed by comparing cartridge usage between individual and pooled Xpert Ultra testing. ResultsA total of 3043 individuals were tested individually and as part of 771 pooled samples. Compared with culture, the overall sensitivities of pooled and individual Xpert Ultra were 85.8% (95% CI: 79.8-90.6) and 89.2% (83.7-93.4), respectively, while specificities were 98.9% (98.4-99.2) and 98.1% (97.5-98.6). Pooled Xpert Ultra detected 100% of the high, medium, and low burden categories identified by individual testing, but showed lower detection for very low (81.8%) and trace (31.4%). Compared with individual testing, pooled testing reduced cartridge use and cost by 55.8%. ConclusionsPooled sputum testing with Xpert Ultra demonstrated high diagnostic performance similar to individual testing, while substantially reducing the cartridge costs. This approach offers a scalable molecular TB testing in resource-limited, high-burden countries such as Bangladesh.