574. Polymerase Chain Reaction (PCR) on Pathology Tissue Samples Improves Clinical Care for Mycobacterium avium complex (MAC) When Diagnostic Uncertainty Remains After Standard Evaluation
Session: Poster Abstract Session: Non-Tuberculosis Mycobacterial
Thursday, October 27, 2016
Room: Poster Hall
Posters
  • NMT PCR Poster Emge et al.pdf (3.6 MB)
  • Background: The clinical relevance of nontuberculous mycobacteria (NTM), such as MAC, is increasingly recognized, especially in the setting of a growing immunocompromised population. Molecular techniques have the potential to improve diagnostics as well decrease time to initiation of appropriate treatment. However, the utility of PCR for the diagnosis of NTM is at yet undefined; for example, PCR is not included in the diagnostic criteria for MAC infection per American Thoracic Society / Infectious Diseases Society of America guidelines. We aimed to evaluate whether PCR on pathology tissue samples may facilitate diagnosis and treatment of patients with suspected MAC infection.

    Methods: This retrospective study was conducted at two tertiary care centers within the Texas Medical Center: Ben Taub Hospital (BTH) and CHI Baylor St. Luke’s Medical Center (BSLMC). Patients with pathology samples sent to the University of Washington for MAC PCR between 2012 and 2015 were identified. Medical records were reviewed and correlated to clinical, pathology and microbiology data.

    Results:

    • BTH – 1/4 cases had positive PCR for MAC from a paraffin-embedded retroperitoneal lymph node with acid-fast bacilli (AFB) seen on pathology; the PCR result enabled clinicians to narrow the treatment regimen before the culture ultimately turned positive for MAC. In 2/3 cases with negative PCR, culture was ultimately positive for MAC.
    • BSLMC – In 2/20 cases, PCR was positive for MAC and enabled the treating physicians to avoid anti-tuberculous therapy. Both positive cases were from lung specimens that were paraffin-embedded and had AFB visualized on pathology. Culture was sent on only one of these samples and was positive. Of the remaining 18 samples negative by PCR, 13 had a negative AFB culture and 2 were positive for another mycobacterial species; in 3 cases culture was not sent.

    Conclusion: Overall, the sensitivity of MAC PCR from a paraffin-embedded pathology sample is low even with visualized AFB; however a positive result is still helpful to guide treatment, particularly when culture data is either delayed or unavailable.

    Drew Emge, M.D., Internal Medicine, Baylor College of Medicine, Houston, TX, Nadine Harris, M.D., Infectious Diseases, Baylor College of Medicine, Houston, TX, Charles Stager, PhD, Pathology, Baylor College of Medicine, Houston, TX, Todd Lasco, PhD, Clinical Laboratory, CHI Baylor St. Luke's Medical Center, Houston, TX and Stacey R. Rose, MD, Internal Medicine, Section of Infectious Diseases, Baylor College of Medicine, Houston, TX

    Disclosures:

    D. Emge, None

    N. Harris, None

    C. Stager, None

    T. Lasco, None

    S. R. Rose, None

    Findings in the abstracts are embargoed until 12:01 a.m. CDT, Wednesday Oct. 26th with the exception of research findings presented at the IDWeek press conferences.