© 2012AOAC INTERNATIONAL
AOACO
FFICIAL
M
ETHODS
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A
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(2012)
G
UIDELINES
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Appendix F, p. 11
ANNEXB
ClassificationofMethods
The following guidance may be used to determine which
performance parameters in Table A1 apply to different
classifications of methods.
AOAC INTERNATIONAL does not
recognize the term “semiquantitative” as a method classification.
Methods that have been self-identified as semiquantitative will be
classified into one of the followingfive types:
Type I: QuantitativeMethods
Characteristics: Generates a continuous number as a result.
Recommendation: Use performance requirements specified for
quantitativemethod (mainor trace component). Use recovery range
andmaximum precision variation inTablesA4 andA5.
In some cases and for some purposes, methodswith less accuracy
andprecision than recommended inTablesA4 andA5may be
acceptable. Method developers should consult with the appropriate
method committee to determine if the recommendations inTables
A4 andA5 do or do not apply to theirmethod.
Type II:Methods that Report Ranges
Characteristics: Generates a “range” indicator such as 0, low,
moderate, and high.
Recommendation: Use performance requirements specified for
qualitativemethods (main component). Specify a range of POD for
each range “range” indicator.
Type III:MethodswithCutoff Values
Characteristics: Methodmay generate a continuous number as an
interim result (such as aCT value for aPCRmethod), which is not
reported but converted to a qualitative result (presence/ absence)
with the use of a cutoff value.
Recommendation: Use performance requirements specified for
qualitativemethods.
Type IV: QualitativeMethods
Characteristics: Method of analysiswhose response is either the
presence or absence of the analyte detectedeither directly or
indirectly in a specified test portion.
Recommendation: Use performance requirements specified for
qualitativemethods.
TypeV: IdentificationMethods
Characteristics: Method of analysiswhose purpose is to determine
the identity of an analyte.
Recommendation: Use performance requirements specified for
identificationmethods.
Figure A2. RelationshipbetweenLOD andLOQ. LOD is
definedas the lowest quantityof a substance that canbe
distinguished from the absenceof that substance (ablank
value) within a stated confidence limit. LOQ is the level above
whichquantitative resultsmaybeobtainedwith a stated
degreeof confidence.
Figure A1. Relationshipbetweenprecisionversusbias (trueness).
Trueness is reportedasbias.Bias isdefinedas thedifference
between the test resultsandanaccepted referencevalue.
Figure A3. HorwitzCurve, illustrating the exponential
increase in the coefficient of variationas the concentrationof
theanalytedecreases [
J.AOAC Int
. 89, 1095(2006)].
