where 𝜇𝜇 0 is the mean LFA reader score for the negative samples, 𝜎𝜎 0 is the corresponding standard deviations, and 𝜎𝜎 𝑙𝑙𝑆𝑆𝑙𝑙 𝑝𝑝𝑆𝑆𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑅𝑅 is the pooled standard deviation for the four lowest non-zero concentrations (0.25, 0.5, 1, 2 ng/mL). The corresponding concentration and associated 95% confidence intervals were then calculated using the fitted curve.