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Evaluation of the Xpert MTB/RIF Performance on Tissues: Potential Impact on Airborne Infection Isolation at a Tertiary Cancer Care Center

  • Tracy McMillen (a1), Shauna C. Usiak (a2), Liang Hua Chen (a1), Luz Gomez (a1), Peter Ntiamoah (a3), Meera R. Hameed (a3), Indre Budvytiene (a4), Niaz Banaei (a4), Mini Kamboj (a2) (a5) and N. Esther Babady (a1) (a5)...

In this study, we sought to evaluate the performance of the Xpert MTB/RIF (Cepheid) assay for the detection of Mycobacterium tuberculosis (MTB) complex DNA on fresh and formalin-fixed, paraffin-embedded (FFPE) tissue specimens from oncology patients in an area with a low prevalence of tuberculosis. We also aimed to retrospectively assess the potential impact of Xpert MTB/RIF on the duration of airborne infection isolation (AII).


A 473-bed, tertiary-care cancer center in New York City.


A total of 203 tissue samples (101 FFPE and 102 fresh) were tested using Xpert MTB/RIF, including 133 pulmonary tissue samples (65.5%) and 70 extrapulmonary tissue samples (34.5%). Acid-fast bacilli (AFB) culture was used as the diagnostic gold standard. The limit of detection (LOD) and reproducibility were also evaluated for both samples types using contrived specimens. The potential impact of the Xpert MTB PCR assay on tissue samples from AII patients on AII duration was retrospectively assessed.


Using the Xpert MTB/RIF for fresh tissue specimens, the sensitivity was 50% (95% CI, 1.3%–98.7%) and the specificity was 99% (95% CI, 94.5%–99.9%). For FFPE tissue specimens, the sensitivity was 100% (95% CI, 63.1%–100%) and the specificity was 98.3% (95% CI, 95.5%–100%. The LOD was 103 colony-forming units (CFU)/mL for both fresh and FFPE tissue specimens, and the Xpert MTB/RIF was 100% reproducible at concentrations 10 times that of the LOD. With an expected turnaround time of 24 hours, the Xpert MTB PCR could decrease the duration of AII from a median of 8 days to a median of 1 day.


The Xpert MTB/RIF assay offers a valid option for ruling out Mycobacterium tuberculosis complex (MTBC) on tissue samples from oncology patients and for minimizing AII resource utilization.

Infect Control Hosp Epidemiol 2018;39:462–466

Corresponding author
Address correspondence to N. Esther Babady, PhD, D (ABMM), Clinical Microbiology Service, Department of Laboratory Medicine, Memorial Sloan Kettering Cancer Center, 327 East 64th Street, CLM 522, New York, New York (
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PREVIOUS PRESENTATION. The results of this study were presented in part at the 2016 American Society of Microbiology Microbe Meeting on June 20, 2016, in Boston, Massachusetts.

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1. US Food and Drug Admistration. New data show test can help physicians remove patients with suspected TB from isolation earlier. FDA website. Published 2015. Accessed January 10, 2018.
2. Luo, RF, Scahill, MD, Banaei, N. Comparison of single-copy and multicopy real-time PCR targets for detection of Mycobacterium tuberculosis in paraffin-embedded tissue. J Clin Microbiol 2010;48:25692570.
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Infection Control & Hospital Epidemiology
  • ISSN: 0899-823X
  • EISSN: 1559-6834
  • URL: /core/journals/infection-control-and-hospital-epidemiology
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