Preliminary Test of Candidate Rapid Diagnostic Test for the Detection of 38 kDa Mycobacterium Tuberculosis Antigen in Saliva

Background and Objectives: Identifying tuberculosis (TB) in pediatric cases is a major challenge in developing countries, as children have problems with expelling sputum, making specific diagnostics crucial. The objective of the study was to develop a rapid test using polyclonal antibodies to detect antigen 38kDa from Mycobacterium tuberculosis in the saliva of TB patients. Materials and Methods: The recombinant protein Ag38 was purified using the Ni-NTA purification kit. Polyclonal antibodies were generated in BALB-c mice using 50 µg/ml of purified Ag38 recombinant protein. A Lateral Flow Assay (LFA) was constructed, employing 5 mg/mL colloidal gold-labelled polyclonal antibody anti-Ag38 in the test line to capture the conjugates, while goat anti-mouse IgG was used in the control line. The LFA was tested in 5 TB patients and 7 healthy person served as negative control. Results: The recombinant protein achieved 95% purity. The rapid test kit, with a detection limit of 5.3 µg/mL, successfully identified Ag38 protein in TB patient saliva (positive control) and not in healthy human serum (negative control). While reproducibility was confirmed for TB patients, results were inconsistent for healthy individuals. Conclusion: The Lateral Flow Assay using polyclonal antibody Ag38 displays promise in detecting M tuberculosis antigen in the saliva of TB patients. Further validation with more TB patient saliva samples is needed to determine LFA sensitivity and specificity.