Diagnostic accuracy of the re-engineered urinary FujiLAM2 assay amongst hospitalized adults with advanced HIV disease.

BACKGROUND

A nonsputum-based, point-of-care tuberculosis (TB) diagnostic test is a global health priority. The impact of urinary mycobacterial lipoarabinomannan (LAM) testing has been limited by the diagnostic performance of current assays. We assessed the diagnostic accuracy of the re-engineered TB-LAM SILVAMP (FujjLAM2) assay (Fujifilm, Japan) to diagnose TB amongst hospitalized adults living with advanced HIV disease.

METHODS

We consecutively enrolled adults presenting with suspected meningitis at two hospitals in Uganda. We implemented a standardized TB diagnostic package: urine Alere TB lipoarabinomannan (TB-LAM), urine Xpert MTB/Rif Ultra, CSF Xpert MTB/Rif Ultra, TB CSF culture, mycobacterial blood culture and chest radiography. We performed FujiLAM2 testing on cryopreserved or fresh urine. We compared diagnostic accuracy against a composite microbiological reference standard of any positive TB test (including Alere-LAM). We assessed 30-day mortality.

FINDINGS: We performed FujiLAM2 testing on urine of 436 hospitalized participants. The median CD4 + cell count was 34 cells/μl [interquartile range (IQR) 11-96]. Using the microbiologic reference standard, FujiLAM2 sensitivity was 34% [95% confidence interval (CI) 25-43%], and specificity was 94% (95% CI 91-96%). When grade-1 Alere TB-LAM positives were excluded, sensitivity was 38% (95% CI 27-50%). Cryopreserved specimens were threefold more frequently positive.

INTERPRETATION: Amongst hospitalized adults with advanced HIV disease, the re-engineered FujiLAM2 urine assay had suboptimal sensitivity but high specificity for diagnosing TB disease. Antigen-antibody/protein complexes may be present accounting for better sensitivity with cryopreserved specimens.