A new mathematical procedure for the assessment of test performance of PSA assays

A new procedure has been worked out and adapted on microsoft Excel that allows to calculate from one set of e.g. 100 triplicate measurements the critical limit, the limit of detection and the power of definition. The limit of detection is defined as the analyte concentration which can be differentiated from the blank with a confidence of > or = 95%. The power of definition defines the number of values that can be differentiated in a certain interval with a predefined probability (e.g. > or = 95%). The lower limit of quantification is obtained graphically from the precision profile as the intersection of a line, representing the maximum acceptable CV, with the upper edge of the confidence interval.