Standard curves based on the four-parameter log-logistic model (FCT) fitted using the four alternative approaches to treat background noise (BKG) in the four emulated datasets after the outliers identified in Fig 5 were flagged (empty circles).

<p>The dashed lines represent the confidence interval of the curve, and the green line represents the geometric mean of the blank controls. RS = R-square. (A) Standard curve fitted using “Ignore” background noise method; (B) standard curve fitted including the background noise as an extra point when fitting the curve, using “Include” background method; (C) standard curve fitted subtracting the background noise using the “Subtract” method; (D) standard curve fitted constraining the lower asymptote to the background noise using the “Constraint” method.</p>