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Diagnostic Usefulness of Bronchoalveolar Lavage Fluid Xpert MTB/RIF in Patients with Suspected Pauci-bacillary Pulmonary Tuberculosis

Abstract Background Rapid and accurate diagnosis of tuberculosis (TB) is important for appropriate treatment initiation and control of disease transmission. Xpert TB/RIF has been widely used for rapid diagnosis especially in sputum AFB smear-negative pulmonary TB. However, about one-third of patients with pauci-bacillary pulmonary TB still reveal negative Xpert TB/RIF results from sputum specimens. Theoretically, bronchoalveolar lavage (BAL) fluid can provide more sensitive specimen in those with sputum-scarce or AFB smear-negative pulmonary TB than sputum.However, there is limited data on the diagnostic performance of Xpert TB/RIF from BAL fluid in patients with pauci-bacillary pulmonary TB. Methods All patients with suspected pulmonary TB who underwent BAL due to sputum-scarcity or negative AFB smear results and underwent Xpert TB/RIF from BAL fluid were retrospectively reviewed at a tertiary hospital, Seoul, South Korea (an intermediate TB-burden country) between October 2014 and April 2017. Confirmed TB was defined to those with clinical specimens positive for M. tuberculosis by culture or PCR assays. Patients those with caseating granuloma in biopsy tissue and shows a good response to anti-tuberculous therapy were classified as having probable TB. Results A total of 113 patients were included in the analysis. Of these 113 patients, 30 (27%) were classified as confirmed TB, 7 (6%) as probable TB, and 76 (67%) as not TB. Of these 37 patients with confirmed or probable TB, 8 (22%) had miliary TB and 12 (32%) were immunocompromised. Only 15 (50%) of the 30 confirmed TB patients revealed positive Xpert TB/RIF results from BAL fluid. Overall sensitivity, specificity, positive predictive value, and negative predictive value of Xpert TB/RIF from BAL fluid for the diagnosis of TB were 41% (95% CI, 31%-41%), 100% (95% CI, 95%-100%), 100% (95% CI 77%-100%), and 78% (95% CI 74%-77%), respectively Conclusion XpertTB/RIF from BAL fluid appears to be suboptimal to rule out pulmonary TB. The development of more sensitive and rapid test for pauci-bacillary pulmonary TB is needed. Disclosures All authors: No reported disclosures.

Background. Rapid and accurate diagnosis of tuberculosis (TB) is important for appropriate treatment initiation and control of disease transmission. Xpert TB/RIF has been widely used for rapid diagnosis especially in sputum AFB smear-negative pulmonary TB. However, about one-third of patients with pauci-bacillary pulmonary TB still reveal negative Xpert TB/RIF results from sputum specimens. Theoretically, bronchoalveolar lavage (BAL) fluid can provide more sensitive specimen in those with sputum-scarce or AFB smear-negative pulmonary TB than sputum.However, there is limited data on the diagnostic performance of Xpert TB/RIF from BAL fluid in patients with pauci-bacillary pulmonary TB.
Methods. All patients with suspected pulmonary TB who underwent BAL due to sputum-scarcity or negative AFB smear results and underwent Xpert TB/RIF from BAL fluid were retrospectively reviewed at a tertiary hospital, Seoul, South Korea (an intermediate TB-burden country) between October 2014 and April 2017. Confirmed TB was defined to those with clinical specimens positive for M. tuberculosis by culture or PCR assays. Patients those with caseating granuloma in biopsy tissue and shows a good response to anti-tuberculous therapy were classified as having probable TB.
Disclosures. All authors: No reported disclosures.

Background. The QuantiFERON Gold-in-tube (QFT) test is an Interferon Gamma Release Assay (IGRA) used to indirectly diagnose tuberculosis infection (TBI). The QFT measures Interferon gamma (INF-γ) released in response to specific
Mycobacterium tuberculosis (Mtb) antigens. The main objective of this analysis is to determine whether there is a seasonal variation of the IFN-γ level released in QFT blood samples.
Methods. Data of the QFT assays conducted in health care workers (HCW) at Houston Methodist Hospital (HMH; Houston, TX) between August 2008 and April 2017 were analyzed and stratified by the season when the blood samples were drawn. Multivariate generalized linear models (GLM) controlling for age, gender and ethnicity were used to estimate IFN-γ measured in the nil and mitogen controls per season.
Results. Data from 10,089 QFT assays were included in the analysis. The tested HCW were primarily between the ages of 18 to 49 years (76.5%), female (65.9%), and non-Hispanic (77.0%). A significantly higher level of IFN-γ was found in the mitogen stimulated blood (Phytohemaglutinin) in the summer (June -August) (estimate: 0.19 IU/mL; P <0.001) compared with the other season, and a significantly lower level of IFN-γ was found in the fall (September -November) (estimate: -0.27 IU/mL; P <0.001) compared with the other seasons. The IFN-γ level was significantly lower in unstimulated blood (estimate: −0.02 IU/mL; P = 0.038) but not in the antigen stimulated blood samples drawn in the winter (December-February) compared with those drawn in other seasons.
Conclusion. We observed a seasonal variation of the IFN-γ level measured in unstimulated and antigen-stimulated blood samples drawn for the QFT assays, in which seasonal factors such as airborne antigens like pollen may play a role. Clinicians should take into account the possible seasonal variation when interpreting positive QFT results, especially those on the borderline of the assay's diagnostic cutoffs.
Re-testing or implementing additional diagnostic tools should be considered if necessary. Further research would be needed to identify the specific seasonal factors that may influence the QFT results.
Disclosures. All authors: No reported disclosures.