Urine lipoarabinomannan concentrations among HIV-uninfected adults with pulmonary or extrapulmonary tuberculosis disease in Vietnam

Lipoarabinomannan (LAM) is a Mycobacterial cell wall glycolipid excreted in urine, and a target biomarker of rapid diagnostic tests (RDTs) for tuberculosis (TB) disease. Urine LAM (uLAM) testing by RDT has been approved for people living with HIV, but there is limited data regarding uLAM levels in HIV-negative adults with TB disease. We conducted a clinical study of adults presenting with TB-related symptoms at the National Lung Hospital in Hanoi, Vietnam. The uLAM concentrations were measured using electrochemiluminescent immunoassays and compared to a microbiological reference standard (MRS) of sputum, GeneXpert Ultra and TB culture. Additional microbiological testing was conducted for possible extrapulmonary TB, when clinically indicated. Among 745 participants enrolled, 335 (44.9 %) participants recruited from the pulmonary TB wards (PR-PTBW) and 6 (11.3%) participants recruited from the EPTB wards (PR-EPTBW) had confirmed TB disease. The MRS positive cohort measured median uLAM concentration for S4-20/A194-01 (S/A) were 14.5 pg/mL and 51.5 pg/mL, respectively. The FIND28/A194-01 (F/A) antibody pair overall and TB-positive cohort measured mean uLAM was 44.4 pg/mL and 78.1 pg/mL, respectively. Overall, the S/A antibody pair had a sensitivity of 39% (95% Confidence Interval [CI] 0.33, 0.44) and specificity of 97% (95% CI 0.96, 0.99) against the MRS. The F/A antibody pair had a sensitivity of 41% (95% CI 0.35, 0.47) and specificity of 79% (95% CI 0.75, 0.84). The areas under the receiver operating curves were 0.748 for S/A and 0.629 for F/A. There was little difference between the S/A median uLAM concentration with pulmonary (55 pg/mL) and extrapulmonary (36 pg/mL) TB disease. With F/A the medians for pulmonary and extrapulmonary TB disease were 79% and 76.5% respectively. Among HIV-negative adults in Vietnam, concentrations of uLAM remained relatively low for people with TB disease, which may present challenges for developing a more sensitive rapid uLAM test.