Complementary effects of acid-fast staining, culture, and Xpert MTB/RIF® on different respiratory tract samples in a referral center

OBJECTIVE: To evaluate diagnostic performance of different combinations of acid-fast staining (AFS), Xpert MTB/RIF (Xpert), and Mycobacterium tuberculosis (MTB) culture across sample types in pulmonary tuberculosis (PTB) in a referral center. METHODS: We conducted a retrospective cross-sectional study on all PTB patients with confirmed microbiological diagnosis in China-Japan Friendship Hospital from January 1st, 2017 to December 31st, 2021. Distribution and sensitivity of different testing strategies were compared for sputum, bronchoalveolar lavage fluid (BALF), and biopsy tissues [transbronchial lung biopsy (TBLB)/transbronchial biopsy (TBB)] using parallel AFS/Xpert/culture combinations. RESULTS: 1,094 microbiologically diagnosed PTB patients were identified. For sputum samples, the most common testing strategy was parallel AFS/Xpert/culture (42.3%), achieving 89.5% (95%CI 85.7%-92.1%) sensitivity. BALF samples demonstrated similar performance with this combination [86.3% sensitivity, (95%CI 82.1%-89.7%)]. In biopsy tissues, the same triad yielded a sensitivity of 73.8% (95%CI 65.0%-81.5%). Xpert and culture showed partially non-overlapping results in all sample types. A subgroup analysis of sputum tested before bronchoscopy showed 56.5% (95%CI 50.2%-62.7%) sputum Xpert sensitivity and 66.7% (95%CI 58.2%-74.2%) culture sensitivity. CONCLUSION: Simultaneous usage of Xpert, AFS and culture on the same specimen increases MTB testing sensitivity on sputum, BALF and TBB/TBLB, which is valuable for early diagnosis for pulmonary tuberculosis in high-burden settings.