Accuracy of a novel urine test, Fujifilm SILVAMP TB LAM, for the diagnosis of pulmonary tuberculosis in children

BACKGROUND: An accurate point-of-care test for tuberculosis in children remains an elusive goal. Recent evaluation of a novel point-of-care urinary lipoarabinomannan test, Fujifilm SILVAMP TB LAM (FujiLAM) in HIV-infected adults showed significantly superior sensitivity than the current Alere Determine TB LAM test (AlereLAM). We therefore compared the accuracy of FujiLAM and AlereLAM in children with suspected tuberculosis.

METHODS: Children hospitalized with suspected tuberculosis in Cape Town, South Africa were enrolled (consecutive admissions plus enrichment for a group of HIV-infected children with tuberculosis), urine collected and biobanked, and sputum tested with mycobacterial culture and Xpert MTB/RIF or Xpert MTB/RIF Ultra. Biobanked urine was subsequently batch tested with FujiLAM and AlereLAM. Children were categorised as having microbiologically-confirmed TB, unconfirmed TB (clinically diagnosed) or unlikely TB.

RESULTS: A total of 204 children were enrolled and had valid results from both index tests as well as sputum microbiological testing. Compared to a microbiological reference standard, the sensitivity of FujiLAM and AlereLAM was similar (42% and 50% respectively), but lower than Xpert MTB/RIF of sputum (74%). Sensitivity of FujiLAM was higher in HIV-infected children (60%) and malnourished children (62%). Specificity of FujiLAM was substantially higher than AlereLAM (92% vs. 66%). Specificity of both tests was higher in children two years or older (FujiLAM 96% and AlereLAM 72%).

CONCLUSION: The high specificity of FujiLAM suggests utility as a 'rule-in' test for children with a high pretest probability of tuberculosis, including hospitalized children with HIV-infection or malnutrition.