Comprehensive Laboratory Evaluation of a Specific Lateral Flow Assay for the Presumptive Identification of Francisella tularensis in Suspicious White Powders and Aerosol Samples

We conducted a comprehensive, multi-phase laboratory evaluation of the Tularemia BioThreat Alert(®) (BTA) test, a lateral flow assay (LFA) for the rapid detection of Francisella tularensis. The study, conducted at 2 sites, evaluated the limit of detection (LOD) of this assay using the virulent SchuS4 strain and the avirulent LVS strain of F. tularensis. In 6-phase evaluation (linear dynamic range and reproducibility, inclusivity, near-neighbor, environmental background, white powder, and environmental filter extract), 13 diverse strains of F. tularensis, 8 Francisella near neighbors, 61 environmental background organisms, 26 white powders, and a pooled aerosol extract were tested. In the 937 tests performed, the Tularemia BTA demonstrated an LOD of 10(7) to 10(8) cfu/mL, with a sensitivity of 100.00%, specificity of 98.08%, and accuracy of 98.84%. These performance data are important for accurate interpretation of qualitative results arising from screening suspicious white powders in the field.