Table 1.
Types of computed observed total error functions of the between-run CV in different media (rows) and different considered biases (columns).
| TEo calculation | Spiking-recovery bias | Average bias | Range-based bias | QCM between-run bias |
|---|---|---|---|---|
| Between-run CV for serum cortisol | TEoSR
(L4, L8) |
TEoAB
(L4, L8) |
TEoRB
(equivalent L4, L8*) |
TEoQCM
(QCM1, QCM2) |
| Between-run CV for urine cortisol | TEoSR
(L4, L8) |
TEoAB
(L4, L8) |
TEoRB
(equivalent L4, L8*) |
TEoQCM.SR
TEoQCM.AB TEoQCM.RB (QCM1, QCM2)† |
AB = average bias; L4 = cortisol concentration of 38.6 nmol/L (1.4 μg/dL); L8 = cortisol concentration of 552 nmol/L (20 μg/dL); QCM = quality control material; RB = range-based bias; SR = spiking-recovery bias; TEo = observed total error.
Ranged-based bias from groups of the comparison study of the closest ranges from those spiked levels.
There is no target value for urine cortisol QCM with the Immulite 2000 Xpi; thus, to calculate TEo, we used 3 other types of biases: SR and RB at a roughly similar concentrations to those of QCM1 and QCM2, and AB. The latter was elected for QC rule determination for urine cortisol.