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

To describe the utilization of electronic medical data resources, including health records and nursing scheduling resources, to conduct a tuberculosis (TB) exposure investigation in a high-risk oncology unit.

A 42-bed inpatient unit with a mix of surgical and medical patients at a large tertiary-care cancer center in New York City.

High-risk subjects and coworkers exposed to a healthcare worker (HCW) with cavitary smear positive lung TB.

During the 3-month exposure period, 270 patients were admitted to the unit; 137 of these (50.7%) received direct care from the index case HCW. Host immune status and intensity of exposure were used to establish criteria for postexposure testing, and 63 patients (45%) met these criteria for first-tier postexposure testing. No cases of active TB occurred. Among coworkers, 146 had significant exposure (ie, >8 hours cumulative). In the 22-month follow-up period after the exposure, no purified protein derivative or interferon gamma release assay conversions or active cases of TB occurred among exposed HCWs or patients.

Electronic medical records and employee scheduling systems are useful resources to conduct otherwise labor-intensive contact investigations. Despite the high-risk features of our index case, a highly vulnerable immunocompromised patient population, and extended proximity to coworkers, we did not find any evidence of transmission of active or latent tuberculosis infection among exposed individuals.

Infect Control Hosp Epidemiol 2017;38:1235–1239