Rapid Genedia TB-LAM Ag test as a potential biomarker of cure after tuberculosis treatment

Introduction:At the end of tuberculosis (TB) treatment, cure is generally determined by clinical evaluation based on the resolution of signs and symptoms.Patients with pulmonary TB often stop producing spontaneous respiratory samples (sputum), making microbiological assessment of treatment efficacy difficult.The low sensitivity of sputum in people living with HIV further aggravates this limitation.In addition, for patients with extrapulmonary TB, obtaining clinical samples to monitor treatment effectiveness is generally not recommended.Therefore, identifying biomarkers to assess cure after TB treatment is of great importance.Objectives: To evaluate the potential of the Genedia TB-LAM Ag rapid test as a biomarker of cure after TB treatment.The hypothesis is that the LAM antigen will no longer be excreted in urine once treatment eliminates the bacillus.Methodology: This retrospective longitudinal study used frozen urine samples from patients treated at the Clinical Research Laboratory on Mycobacterioses (LaPClin-TB) of the Evandro Chagas National Institute of Infectious Diseases (INI), in Rio de Janeiro, Brazil.Samples were obtained from patients with confirmed TB (Xpert MTB/RIF Ultra and/or culture for Mycobacterium tuberculosis), with and without HIV infection, collected at three time points during TB treatment: treatment initiation (baseline visit, before or up to 7 days after treatment initiation), mid-treatment (2 months), and end of treatment.The Genedia TB-LAM Ag test was performed according to the manufacturer's instructions, and results were read using the GENEDIA Quantum FR101 device, providing qualitative results (positive, negative, or invalid).Results: A total of 22 individuals who achieved cure at the end of treatment were evaluated.At baseline, all samples tested positive for the Genedia TB-LAM Ag test (100%).After two months of treatment, 5 of 22 urine samples showed negative results (22.7%).This proportion increased significantly by the end of treatment, when 18 of 22 samples were negative (81.8%; p < 0.001) in the rapid test. Conclusion:The results suggest that detection of the LAM antigen by the Genedia TB-LAM Ag test decreases over the course of TB treatment, possibly reflecting the reduction in bacillary load during therapy, particularly after completion of treatment.These findings indicate that the GENEDIA TB-LAM Ag test has potential as a biomarker of cure, although studies with larger sample sizes are needed to confirm this applicability.