Xpert® MTB/RIF Shortens Airborne Isolation for Hospitalized Patients with Presumptive Tuberculosis in the United States

Background. In the United States, individuals with presumptive pulmonary tuberculosis are placed in airborne infection isolation (AII) and assessed by smear microscopy on three respiratory specimens collected 8-24 hours apart. Xpert (R) MTB/RIF (Xpert) on one, two, or three specimens may be more efficient for determining AII discontinuation. Methods. This single-center, observational cohort study of inpatients with presumptive pulmonary tuberculosis enrolled adults with one or more sputum specimens submitted for smear microscopy. Smear microscopy and Xpert were performed on each sputum specimen. Clinicians were blinded to Xpert results. Primary end point was AII duration. Secondary end points were laboratory processing time, strategy-based tuberculosis detection, and sensitivity and specificity. Results. Among 207 subjects, the median AII duration was 68.0 hours (interquartile range (IQR): 47.1, 97.5) for smear microscopy compared to 20.8 hours (IQR: 16.8, 32.0) for the one-specimen Xpert, 41.2 hours (IQR: 26.6, 54.8) for the two-specimen Xpert, and 54.0 hours (IQR: 43.3, 80.0) for the three-specimen Xpert strategies (p <= 0.004). Median laboratory processing time for smear microscopy was 2.5 times as long as Xpert (p<0.001). The two-and three-specimen Xpert, and smear microscopy strategies captured all six tuberculosis cases. The one-specimen Xpert strategy missed one case. No difference was observed between smear microscopy and Xpert in sensitivity or specificity for detection of Mycobacterium tuberculosis. Conclusions. Xpert-based strategies significantly reduced AII duration compared to the smear-based strategy. The two-specimen Xpert strategy was most efficient in minimizing AII time while identifying all tuberculosis cases among individuals with presumptive tuberculosis in this low-burden setting.