The cut-point of the assay is the level of response of the assay that defines the sample response as positive or negative. Establishing the appropriate cut-point is critical to minimizing the risk of false-negative results. The confirmation cut points are determined by assaying a set of approximately 50 drug-naive individual serum samples over three days by two analysts for a total of six runs. Here, we describe the stepwise procedure to calculate the statistical cut point using the parametric and robust parametric method. Steps for estimating confirmation cut points 1) Compile the data from 50 drug-naive individuals assayed by two analysts over 3 days for a total of six days. (See template below) 2) Compute the % Signal Inhibition or % Immunodepletion from the assay signal generated in the presence and absence of the drug. 3) Use the box plot analysis in JMP to identify and exclude outliers. 4) Use the Shapiro-Wilk Test for the ...