VIDAS3® TB-IGRA assay: evaluation of performance characteristics in a predominantly low risk, low incidence population.

OBJECTIVES: To evaluate the analytical performance of the TB-IGRA® assay on the VIDAS3 platform (bioMérieux) when testing a predominantly low risk population in a low incidence area.

RESULTS: Eighty-eight percent of the results were concordant between QuantiFERON®-TB Gold-Plus (QFT®-Plus, QIAGEN) and TB-IGRA®. All 12 of 99 (12.1%) discordant results were determined positive only with the TB-IGRA® assay. In 11 of 12 of these discordant cases, no explanation could be found in the medical record. Five of these discrepant results were probably caused by the use of contaminated stimulation reagents. The remaining 6 discrepant samples were also part of the reproducibility experiment and only 2 results were reproducible positive. Overall, in the reproducibility experiment 5 of 25 (20.0 %) results were not repeatable.

CONCLUSIONS: the TB-IGRA® assay seems prone to contamination. Besides, we documented a reproducibility of only 80.0% with the TB-IGRA® assay.