AOAC GFA Stakeholder Program Meeting Book (August 27, 2023)

Enhanced Approaches

Limit of Detection (LOD) • Estimated based on observed precision in matrix studies (i.e., not only blanks or calibrants) • LOD Definition: The lowest concentration or mass of analyte in a test sample that can be distinguished from a true blank sample at a specified probability level (ISO 5725-1:1994) • Require evaluation of the effect of concentration on variance in SLV studies (as previously considered for collaborative data)

o Simple formulas (i.e., LOD = x (0) + 3s (0) ) assume equivalent variance o Immunoassays: variance typically increases with concentration o  Better control of false-positives ( α ) and false-negatives ( β )