The following approaches are commonly used for setting a peak reporting threshold:
- Approach 1: Peaks fulfilling the area criteria of ≥3 times the control and equal to or higher than the area of an external standard of specified concentration
- Approach 2: Peaks fulfilling the area criteria of ≥3 times the control and ≥Y% of an internal standard of specified concentration.
Y is selected based on the concentration and response of the internal standard and the analytical evaluation threshold (AET). The AET is related to the drug dosing, which is unknown. A general AET of 0.1µg/mL (ppm) is thus used in the BioPhorum protocol. This corresponds to a drug intake of ~10mL/day, which covers many drug products.