Impact of GeneXpert MTB/RIF on Triage of Respiratory Isolation Rooms for Inpatients with Presumed TB: A Hypothetical Trial. Placing inpatients with presumed active pulmonary tuberculosis in respiratory isolation pending results of serial sputum acid-fast bacilli (AFB) smear microscopy is standard practice in high-income countries. However, this diagnostic strategy is slow and yields few TB diagnoses. We sought to determine if replacing microscopy with the GeneXpert MTB/RIF (Xpert) nucleic-acid amplification assay could reduce testing time and usage of isolation rooms. We prospectively followed inpatients at San Francisco General Hospital undergoing TB evaluation. We performed smear microscopy and Xpert testing on concentrated sputum, and calculated diagnostic accuracy for both strategies in reference to serial sputum mycobacterial culture. We measured turn-around time for microscopy and estimated hypothetical turn-around times for Xpert on concentrated and unconcentrated sputum. We compared median and total isolation times for microscopy to those estimated for the two Xpert strategies.
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