Ultra-sensitive urinary lipoarabinomannan (LAM) immunoassay for tuberculosis detection: a performance evaluation

Area of Science:

• Infectious Disease Diagnostics
• Biomarker Detection
• Assay Development

Background:

• Global priority for rapid, non-sputum Tuberculosis (TB) diagnostic tests to expedite treatment.
• Current WHO-recommended rapid diagnostic test (Alere Determine TB Lipoarabinomannan Ag) has suboptimal sensitivity.
• Laboratory-based electrochemiluminescence LAM assay (EclLAM) is the benchmark for urinary LAM detection.

Purpose of the Study:

• To assess the diagnostic accuracy of an ultra-sensitive Plasmonic Fluor-linked Immunosorbent LAM assay (PFLISA-LAM).
• To compare PFLISA-LAM performance against Sputum Xpert MTB/RIF, sputum culture, and urine EclLAM.
• To evaluate PFLISA-LAM's potential to improve TB diagnosis.

Main Methods:

• Development and evaluation of the PFLISA-LAM assay.
• Preclinical study with 337 urine samples for cutoff determination and initial performance evaluation against Sputum Xpert MTB/RIF and culture.
• Diagnostic accuracy study with 77 blinded urine samples comparing PFLISA-LAM and EclLAM against a microbiological reference standard.

Main Results:

• PFLISA-LAM demonstrated a limit of detection of 0.84 pg/mL for purified LAM in urine.
• In diagnostic accuracy assessment, PFLISA-LAM showed 73% sensitivity and 98% specificity, outperforming EclLAM (42% sensitivity, 95% specificity).
• Combining PFLISA-LAM with Sputum Xpert MTB/RIF improved overall sensitivity to 76%.

Conclusions:

• PFLISA-LAM exhibits superior analytical and diagnostic sensitivity for detecting urinary LAM in TB-positive individuals compared to EclLAM.
• The PFLISA-LAM assay enhances diagnostic value for urinary LAM detection.
• PFLISA-LAM serves as a valuable complement to molecular tests, improving TB diagnostic outcomes.