Approach to the use of Xpert MTB/RIF assay to make decisions regarding need for airborne infection isolation in adults

The Xpert MTB/RIF assay has been approved by the United States Food and Drug Administration for use in place of serial acid-fast sputum smears to aid in decisions regarding whether continued airborne infection isolation is warranted for patients with suspected tuberculosis. The approach described above should not be used alone to rule out tuberculosis; Xpert-negative or AFB smear-negative sputum may contain viable organisms and represent infectious tuberculosis. Interpretation of Xpert results must be made in the context of clinical and radiographic findings. In addition, at least three sputum specimens should be obtained for AFB smear and culture, which must be performed for detection of Mycobacterium tuberculosis complex and antimicrobial susceptibility testing.
Negative Xpert results with positive AFB smear results should prompt consideration of nontuberculous mycobacteria infection (refer to related UpToDate content).
Procedures must comply with state and local public health regulations; for questions, contact your local public health authority.
Institutional infection control, in collaboration with the tuberculosis laboratory and public health authority, should collect and analyze data to determine and evaluate the effectiveness of the methods used to determine discharge from AII and modify this protocol as necessary.

TB: tuberculosis; AII: airborne infection isolation; AFB: acid-fast bacilli.
* First morning sputum specimen is preferred to maximize diagnostic yield. Protocols for sputum collection are provided in the reference below. Sputum quality is critical for the performance of this assay. Spontaneously expectorated sputum obtained following deep coughing or sputum obtained following an approved procedure for sputum induction with deep inhalation of aerosolized hypertonic saline and deep coughing may be used. Saliva is not acceptable.
¶ An invaild Xpert result represents a failure of the assay; this is estimated to occur in 1 to 2 percent of specimen runs; in such cases, the presence or absence of M. tuberculosis complex cannot be determined.
Δ In such circumstances, a positive results suggests TB is likely, a negative result suggests infectious TB is not likely, and an invalid result indicates that the likelihood of infectious TB cannot be determined based on Xpert results. In such cases, AFB smear results and clinical judgment should be used to make decisions regarding likelihood of infectious TB and timeframe for discontinuation of AII.

Modified from: National Tuberculosis Controllers Association and Association of Public Health Laboratories: Consensus statement on the use of Cepheid Xpert MTB/RIF assay in making decisions to discontinue airborne infection isolation in healthcare settings. Available at: http://www.tbcontrollers.org/docs/resources/NTCA_APHL_GeneXpert_Consensus_Statement_Final.pdf (Accessed on April 27, 2016).

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Approach to the use of Xpert MTB/RIF assay to make decisions regarding need for airborne infection isolation in adults