Longitudinal urinary LAM measurements in pulmonary tuberculosis patients: preliminary observations

BACKGROUND: Monitoring treatment response in pulmonary tuberculosis (TB) is critical, but non-invasive biomarkers are limited for patients unable to produce sputum. OBJECTIVE: To evaluate the utility of the PATHFAST TB LAM Ag assay in urine for diagnosis and treatment monitoring of pulmonary TB. METHODS: Nine patients with confirmed TB at the University Hospital of Larissa, Greece, were followed longitudinally. Urine samples were collected at treatment initiation and at weeks 2, 4, 8, 12, 16, 20, and 24. Lipoarabinomannan (LAM) concentrations were measured using the PATHFAST TB LAM Ag assay; values ≥ 10 pg/mL were considered positive. RESULTS: Urinary LAM positivity peaked between weeks 4 and 12. Three kinetic patterns emerged: (i) early pronounced decline in patients with high baseline LAM; (ii) modest decreases in intermediate baseline patients; and (iii) variable or rising trajectories in low-baseline patients. Patterns mirrored previously reported sputum LAM kinetics. One patient treated on clinical criteria alone showed baseline positivity, and two patients with non-tuberculous mycobacterial infection also tested positive. CONCLUSIONS: Urinary LAM kinetics closely mirror sputum-derived patterns, supporting urine as a non-invasive specimen for serial TB monitoring. Interpretation of low-baseline results requires caution, and further studies with larger cohorts are warranted.