B99-03 Use of Lateral Flow Lipoarabinomannan Assay and Different Levels of ADA in Pleural Fluid for Tuberculosis Diagnosis in a High Burden Country

Abstract Rationale Pleural tuberculosis (PlTB) is the commonest extrapulmonary presentation of the disease, being a paucibacillary manifestation and presenting a compartmentalized immune response, which adds difficulties to its diagnosis. The Lateral-Flow Lipoarabinomannan assay (LF-LAM) is a rapid diagnostic tool based on the detection of mycobacterial LAM antigen in urine, standardized as a point-of-care for TB-HIV co-infection diagnosis. We aimed to investigate the potential use of LF-LAM assay on pleural fluid (PF) samples from patients with pleural effusion due to PlTB and other diagnoses. Methods A cross-sectional study was conducted using serum and pleural fluid (PF) samples, stored at -80 °C in a biorepository, from patients with non-HIV PlTB and other non-TB diagnoses, recruited at Pedro Ernesto University Hospital, Rio de Janeiro State University, Rio de Janeiro, Brazil. Serum and PF samples were thawed and subsequently tested using the LF-LAM assay. The performance of the test was compared with smear microscopy, mycobacterial culture, rapid molecular test, histopathology, and adenosine deaminase (ADA) levels. Results A total of 168 serum samples were tested using the LF-LAM assay: 78 from pleural tuberculosis (PlTB) cases and 90 from non-PlTB cases. Additionally, 226 pleural fluid (PF) samples were subjected to LF-LAM testing: 130 from non-tuberculosis (non-TB) cases and 96 from PlTB cases. Among serum samples, 42.3% of the PlTB group showed a positive reaction, while the non-PlTB group showed 85.6% negative results. On PFsamples, 53.1% of the PlTB group showed a positive reaction, while the non-PlTB group showed 90.8% negative results. Mycobacterial culture, smear microscopy, rapid molecular test, histopathology, and ADA at cut-off points ≥ 40 U/L and ≥ 25 U/L showed concordance with LF-LAM in PF samples of 73.45%, 72.3%, 63.46%, 73.39%, 73.21%, and 70.81%, respectively. The association of LF-LAM with ADA ≥ 40 U/L increased specificity and PPV. When combined with ADA ≥ 25 U/L, both specificity and PPV were increased. Conclusions The results of our sample demonstrated an interesting performance of the LF-LAM assay in PF potentially contributing to the screening for the diagnosis of PlTB among patients with pleural effusion under investigation, and enabling the rapid initiation of anti-TB treatment. This abstract is funded by: None