Diagnostic Accuracy of the Updated FujiLAM II Assay to Detect Tuberculosis in Outpatients With Advanced HIV Disease.

BACKGROUND

An urgent need exists for point-of-care diagnostics to detect tuberculosis (TB) among people with advanced human immunodeficiency virus (HIV) disease. The Fujifilm SILVAMP TB LAM (FujiLAM II) is a novel point-of-care assay that detects mycobacterial lipoarabinomannan (LAM) antigen in the urine to identify TB. We present a validation of the FujiLAM II assay on prospectively collected urine samples from outpatient adults with advanced HIV disease in Uganda.

METHODS

We performed a prospective diagnostic accuracy study of the FujiLAM II assay among outpatients with advanced HIV disease at 16 clinics Uganda. FujiLAM II was run on cryopreserved urine. We determined diagnostic performance for the FujiLAM II test against the cases of confirmed TB (Xpert or mycobacterial culture positive) versus cases without TB. We additionally assessed sensitivity and specificity of the FujiLAM II assay as compared with confirmed TB among pre-specified subgroups: CD4 <100 cells/µL versus 100-200 cells/µL, antiretroviral therapy (ART) naive versus experienced, and CRP <5 mg/L versus ≥5 mg/L.

RESULTS

Among 583 participants who had FujiLAM II testing performed, the FujiLAM II assay demonstrated 54% (25/46) (95% confidence interval [CI]: 40%-69%) sensitivity to identify confirmed TB and 95% (326/342) (95% CI: 93% to 98%) specificity to identify the absence of TB. Among participants with CD4 cell counts <100 cells/µL, FujiLAM II sensitivity was 69% (95% CI: 53%-85%) and specificity was 94% (95% CI: 90%-97%). Among participants with serum C-reactive protein (CRP) ≥5 mg/L, the FujiLAM II assay exhibited a sensitivity of 62% (95% CI: 46%-77%) and specificity of 93% (95% CI: 89%-98%).

CONCLUSIONS

FujiLAM II is a point-of-care, non-sputum based TB diagnostic with moderate sensitivity and high specificity in outpatients with advanced HIV disease.