Urine TB test fails in Ugandan children under five

Diagnosing tuberculosis in young children is difficult: the disease often has few bacteria (paucibacillary), symptoms that are not specific, and collecting reliable samples is hard. New, simple tests are therefore urgently needed, especially in settings with high TB burden. Mirembe Angella Nanteza and colleagues set out to assess one such test, FujiLAM version 1, which is a urine-based assay that could offer an easier sample to collect in children. The evaluation was done in Uganda as a cross-sectional study nested within the NOD-pedFEND diagnostic study. Children under five years who had signs or symptoms suggesting tuberculosis were recruited from three hospitals. At the baseline visit, every child underwent a thorough diagnostic workup: culture and Xpert MTB/RIF Ultra on reference samples, and chest X-ray were all performed. The study used the combined results of culture and Xpert MTB/RIF Ultra to define a microbiological reference standard. FujiLAM version 1 testing was carried out on fresh urine collected at that same baseline visit, allowing a direct comparison between the urine test and the established microbiological reference methods.

A total of 79 children under five were included in this evaluation. Using the microbiological reference standard based on culture and Xpert MTB/RIF Ultra, 15 participants (19%) were classified as having microbiologically confirmed TB. Forty-four children (56%) were classified as unconfirmed TB, thirteen (16%) as unlikely TB, and seven participants (9%) were unclassifiable. FujiLAM version 1 testing on fresh urine produced a positive result in only one participant. That child had been classified as unlikely TB, and importantly, both culture and Xpert MTB/RIF Ultra on the reference samples were negative for that participant. When the researchers compared FujiLAM version 1 results against the microbiological reference standard, the sensitivity was 0% with a 95% confidence interval of 0 to 21.8%. In other words, FujiLAM version 1 did not detect any of the cases confirmed by culture or Xpert MTB/RIF Ultra in this group of young children.

These findings led the authors to conclude that FujiLAM version 1 has poor diagnostic accuracy in children under five and is not suitable as a diagnostic test in this age group. The result is important because a urine test that worked well would have offered an easier, noninvasive option for diagnosing pediatric TB, but FujiLAM version 1 did not perform as hoped in this study. The study underscores the ongoing challenge of finding reliable diagnostics for young children, where low bacterial numbers and non-specific illness make microbiological confirmation difficult. The authors recommend further evaluation of an improved assay, specifically an optimized FujiLAM version 2, to determine whether revisions to the test can deliver the accuracy needed for clinical use in young children.