Figure -The dose response curve for an LFA using irradiated virus, as measured using a commercially available optical LFA reader. The LOD is indicated by the dotted lines and was calculated as 23 TCID50/mL (95% CI of 9.1 to 37 TCID50/mL), equivalent to 1.4x10 5 copies/mL (95% CI of 5.5x10 4 to 2.3x10 5 copies/mL). Using a conversion factor of 1:6,071,4 for TCID50/mL to copies/mL for this lot of irradiated virus, the LOD in infectious units was 7.04 TCID50/mL (95% CI of 3.33 to 10.75). Irradiated virus concentration (TCID50/mL) diluted solution of viral fluid. The WHO target product profile lists its desired performance characteristics in terms of viral copies per mL. Unfortunately, lot to lot variability complicates a direct comparison of TCID50 / mL and copies per mL.