AOAC Guidance on FA Immunoassay Validation (August 2023)

1639 1640

Example Data

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35

y = 0.0755x + 0.1368 R² = 0.8857

Deviation

0

0.5

1

1.5

2

2.5

3

Intermediate Precision Standard

Mean Observed Concentration (ppm)

= ( ̅ ( 0 ) +3.3× ( 0 ) ) (1 − 1.65× ) = ( ( 0 1 .04+3.3×0.1368) − 1.65 × 0.0755) = 0.56

1641 1642 1643 1644 1645 1646 1647 1648 1649 1650 1651 1652 1653 1654 1655 1656 1657 1658 1659 1660 1661 1662

2.2. Limit of Quantification (LOQ)

2.2.1. Data required: mean concentration and intermediate precision standard deviation values

from above, linear regression for S i vs. concentration

2.2.2. Model %RSD i across a range of concentrations below and above the expected LOQ using

linear regression and S i(0) above

Linear Regression: = × + ( 0 ) %RSD i Modeling: % =100× ( × + ( 0 ) )

2.2.3. Plot %RSD i vs. mean concentration

2.2.4. Estimate LOQ by calculating the concentration at which %RSD i would meet acceptable levels (e.g., maximum %RSD i prescribed in an SMPR). The estimated LOQ must also be

greater than the estimated LOD.

2.2.5. Values used as estimates of S i(0) should be the same as those used for the LOD calculations.