Use of a Single Xpert MTB/RIF Assay to Determine the Duration of Airborne Isolation in Hospitalized Patients With Suspected Pulmonary Tuberculosis

Abstract

BACKGROUNDHospitalized patients with suspected tuberculosis (TB) are placed in airborne isolation until 3 sputum smear samples are negative for acid-fast bacilli (AFB). The Xpert MTB/RIF assay ("Xpert") nucleic acid amplification test (NAAT) to identify Mycobacterium tuberculosis DNA and resistance to rifampicin is superior to AFB sputum smear microscopy for the diagnosis of TB.OBJECTIVETo compare the performance of a single Xpert to AFB smear microscopy for time to airborne infection isolation (AII) discontinuation.METHODSConsecutive patients over 17 years of age in AII for suspected pulmonary TB between October 1, 2014, and March 31, 2016, with leftover respiratory AFB samples were enrolled in this study. A single Xpert was performed on the first available sample. Demographic, clinical, and microbiological data were recorded for each patient. We compared the duration of AII using a single Xpert to AFB smear microscopy under multiple theoretical scenarios using Kaplan-Meier cumulative incidence curves and the log-rank test.RESULTSIn total, 131 samples were included in our performance analysis of the Xpert, and 114 samples were included in our AII analysis. Overall, 81 patients (65%) were immunosuppressed, of whom 46 (37%) were positive for human immunodeficiency virus (HIV). The sensitivity and specificity of Xpert for diagnosis of M. tuberculosis infection were 67% and 100%, respectively. Xpert was negative in all cases of nontuberculous mycobacteria. Use of a single Xpert reduced AII duration from a median of 67 hours per patient to 42 hours with usual reporting, to 26 hours with direct communication, and to 12 hours with immediate testing.CONCLUSIONSA single negative Xpert result can reduce AII duration compared to the AFB smear microscopy technique under multiple theoretical scenarios.Infect Control Hosp Epidemiol 2018;39:590-595.

Decision making to discharge patients from airborne infection isolation rooms: The role of a single GeneXpert MTB/RIF strategy in Brazil

“…Discontinuation of respiratory isolation based on the molecular test would reduce hospital expenditures and facilitate the reallocation of resources in deficient areas without compromising occupational risk. 16 Although theoretical, our model represents real scenarios of clinical practice and demonstrates, as have other studies such as Chaisson et al 8 and Poonwala et al, 14 a high single GeneXpert MTB/RIF NPV (ie, 99% in both studies) that is even higher than the NPV of sequential AFB smears. In our study, in group 3, a single GeneXpert MTB/RIF showed performance similar to that of 3 AFB smears, but in a shorter period.…”

“…12,13 Recent studies have demonstrated the possibility of using only 1 GeneXpert MTB/RIF to determine the continuation of respiratory isolation because performing >1 molecular test did not produce a superior result. 8,14,15 The economic importance of early patient removal from isolation beds has also been emphasized. 16 Cowan et al 13 estimated a shorter median of hospitalization in airborne isolation with the single GeneXpert MTB/RIF strategy, which would result in a cost savings of up to US$11,466 per patient compared to AFB smear.…”

“…Poonwala et al 14 applied an active model of improvement in communication and logistics from hospital admission to the release of the molecular test results, and they obtained a time of only 12 hours for patient removal from airborne isolation. In the traditional model, these researchers also obtained values of 65 hours.…”

Added Value of Xpert MTB/RIF Ultra for Diagnosis of Pulmonary Tuberculosis in a Low-Prevalence Setting

“…Finally, a positive correlation of Xpert and Ultra semiquantitative results was found with the smear microscopy results, which could guide airborne isolation measures. This could reduce the time to isolation in emergency services in low-prevalence setting (1, 3, 4). In our institution, we consider patients with negative Ultra results to be likely to be smear negative.…”

“…Xpert displays reduced turnaround time and shortened patient isolation and time to initiate anti-TB drugs and is more sensitive and specific than smear microscopy for acid-fast bacillus (AFB) detection. This test is now recommended to initiate the microbial diagnosis of tuberculosis (1–3), as well as to address patient’s transmission potential based on the semiquantitative result (1, 4, 5). Despite a very low limit of detection (LOD; ∼131 CFU/ml), Xpert remains less sensitive than liquid culture (LOD ∼1 to 50 CFU/ml) (6).…”