Figure 6.
Example of utilization of a normalized operational process specifications (OPSpec) chart, at N = 2 levels of QCM, and Ped of the system = 90%, for QC rule validation of L4 (38.6 nmol/L [1.4 μg/dL]) in green, and QCM1 (193 nmol/L [7.0 μg/dL]) in purple. In this example, we are considering the averaged bias (from the comparison study) for QC rule determination of L4 used as a QCM (L4AB). First, CV and bias are determined, and TEo is calculated. Then, a given level of TEa is chosen. Here, when TEo was <20%, TEa was chosen as 20% (QCM1); when TEo was >20%, TEa was chosen as 33% (L4AB). Then, CV and bias are expressed as % of TEa (“normalized”), and those values are plotted on the x-axis and y-axis of the OPSpec chart, respectively, as the “operating point.” All the QC rules to the right of the operating point are candidates for use with the specified Ped and Pfr; all the QC rules left from the operating point are not. Thus, there is no candidate QC rule for L4AB. For QCM1, 12.5s or 13s/22s/R4s would be candidate QC rules; 12s should be avoided because of the Pfr of 0.09 (see discussion). AB = averaged bias; CV = coefficient of variation; L4 = level 4 in this study, corresponding with 1.4 μg/dL; N = number of levels tested for QC; OPSpec = operational process specifications; Ped = probability of error detection; Pfr = probability of false rejection; QCM = quality control material; R = number of repeats for each QC level; TEa = allowable total error; TEo = observed total error.