Table 3.
Reverse approach (Fig. 2B) for QC rule validation for commercial QCM (K9CON for serum, Liquicheck for urine), at low (insufficient), intermediate (optimized), and high (excessively high) TEa for the system, using EZ Rules 3, for n = 2 QCM levels.
| Increasing TEaQCM | Low TEaQCM: 20% | Optimized TEaQCM (σ = 5) | High TEaQCM: 50% | |||||
|---|---|---|---|---|---|---|---|---|
| Serum | QCM1 | Sigma | σ = 4.8* | TEa = 20.8%* | σ = 12.1 | |||
| CV = 4.1% | QC rule | Ped | Pfr | Ped | Pfr | Ped | Pfr | |
| Bias = 0.3% | 12S | 0.99 | 0.09 | 1 | 0.09 | 1.00 | 0.09 | |
| TEo = 8.5% | 12.5S | 0.93 | 0.03 | 0.96 | 0.03 | 1.00 | 0.03 | |
| 13S | 0.80 | 0.00 | 0.86 | 0.00 | >0.98 | 0.00 | ||
| 13S/22S/R4S | 0.91 | 0.01 | 0.94 | 0.01 | 1.00 | 0.01 | ||
| QCM2 | Sigma | σ = 2.8 | TEa = 35.5% | σ = 7.1 | ||||
| CV = 7% | QC rule | Ped | Pfr | Ped | Pfr | Ped | Pfr | |
| Bias = 0.5% | 12S | 0.35 | 0.09 | 1 | 0.09 | 1.00 | 0.09 | |
| TEo = 14.5% | 12.5S | 0.16 | 0.03 | 0.96 | 0.03 | 1.00 | 0.03 | |
| 13S | 0.06 | 0.00 | 0.86 | 0.00 | >0.98 | 0.00 | ||
| 13S/22S/R4S | 0.08 | 0.01 | 0.94 | 0.01 | 1.00 | 0.01 | ||
| Urine | QCM1 | Sigma | σ = 3.5 | TEa = 28.1% | σ = 9.1 | |||
| CV = 5.4% | QC rule | Ped | Pfr | Ped | Pfr | Ped | Pfr | |
| Bias† = 1.1% | 12S | 0.72 | 0.09 | 1 | 0.09 | 1.00 | 0.09 | |
| TEo = 11.9% | 12.5S | 0.48 | 0.03 | 0.96 | 0.03 | 1.0 | 0.03 | |
| 13S | 0.25 | 0.00 | 0.86 | 0.00 | >0.98 | 0.00 | ||
| 13S/22S/R4S | 0.59 | 0.01 | 0.94 | 0.01 | 1.0 | 0.01 | ||
| QCM2 | Sigma | σ = 4.2 | TEa = 23.6% | σ = 10.9 | ||||
| CV = 4.5% | QC rule | Ped | Pfr | Ped | Pfr | Ped | Pfr | |
| Bias† = 1.1% | 12S | 0.91 | 0.09 | 1 | 0.09 | 1.00 | 0.09 | |
| TEo = 10.1% | 12.5S | 0.77 | 0.03 | 0.96 | 0.03 | 1.0 | 0.03 | |
| 13S | 0.57 | 0.00 | 0.86 | 0.00 | >0.98 | 0.00 | ||
| 13S/22S/R4S | 0.69 | 0.01 | 0.94 | 0.01 | 1.0 | 0.01 | ||
Optimized TEa of the system, usually the intermediate one, has been set up for sigma approaching 5; one exception is QCM1 for serum, for which sigma already approaches 5 at “low” TEa (20%). The validated QC rules are those with bold Ped and Pfr, verifying at the same time Ped > 0.9 and Pfr < 0.05.
AB = average bias; Ped = probability of error detection (by the QCM); Pfr = probability of false rejection (by the QCM); QC = quality control; QCM = quality control material; RB = range-based bias; σ = sigma metric; SR = spiking-recovery bias; TEo = total allowable error; TEo = observed total error; K9CON (Immulite Systems Control; Siemens); Liquicheck (Bio-Rad).
For serum QCM1, performance parameters (CV, bias, TEo) were so good that the elected low TEa was already enough to generate a sigma approaching 5.
For the urine QCM, given that no target values were provided by the manufacturer for this method, TE calculations have been done with the global bias of the comparison study (see discussion for justification).