2014 ERP New Member Book

AOACO FFICIAL M ETHODS OF A NALYSIS (2012)

G UIDELINES FOR S TANDARD M ETHOD P ERFORMANCE R EQUIREMENTS 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 A1. Relationshipbetweenprecisionversusbias (trueness). Trueness is reportedasbias.Bias isdefinedas thedifference between the test resultsandanaccepted referencevalue.

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 A3. HorwitzCurve, illustrating the exponential increase in the coefficient of variationas the concentrationof theanalytedecreases [ J.AOAC Int . 89, 1095(2006)].

© 2012AOAC INTERNATIONAL