© 2012AOAC INTERNATIONAL
AOACO
FFICIAL
M
ETHODS
OF
A
NALYSIS
(2012)
G
UIDELINES
FOR
S
TANDARD
M
ETHOD
P
ERFORMANCE
R
EQUIREMENTS
Appendix F, p. 7
Table A2. Recommendeddefinitions
Bias
Difference between the expectation of the test results and an accepted reference value. Bias is
the total systematic error as contrasted to random error. Theremay be one ormore systematic
error components contributing to the bias.
Environmental interference
Ability
of theassay to detect target organism in the presence of environmental substances and
to be free of cross reaction from environmental substances.
Exclusivity
Strains or isolates or variants of the target agent(s) that themethodmust not detect.
Inclusivity
Strains or isolates or variants of the target agent(s) that themethod can detect.
Laboratory probability of detection (POD)
Overall fractional response (meanPOD=CPOD) for themethod calculated from the pooled
POD
j
responses of the individual laboratories (
j
= 1, 2, ...,
L
).
a
SeeAnnexC
.
Limit of quantitation (LOQ)
Minimum concentration ormass of analyte in a givenmatrix that can be reported as a
quantitative result.
POD (0)
Probability of themethod giving a (+) responsewhen the sample is trulywithout analyte.
POD (c)
Probability of themethodgiving a (–) responsewhen the sample is trulywithout analyte.
POD
Proportionof positive analytical outcomes for a qualitativemethod for a givenmatrix at a given
analyte level or concentration. Consult
AnnexC
for a full explanation.
Probability of identification (POI)
Expected or observed fraction of test portions at a given concentration that gives positive result
when tested at a given concentration. Consult
Probability of Identification (POI): AStatistical
Model for theValidation of QualitativeBotanical IdentificationMethods
.
c
Precision (repeatability)
Closeness of agreement between independent test results obtained under stipulated
conditions. Themeasure of precision is usually expressed in terms of imprecision and
computed as a standard deviation of the test results.
d
Recovery
Fraction or percentage of the analyte that is recoveredwhen the test sample is analyzed using
the entiremethod
. Thereare
two types of recovery: (
1
) Total recovery basedon recovery of
the native plus added analyte, and (
2
)marginal recovery based only on the addedanalyte (the
native analyte is subtracted from both the numerator and denominator).
e
Repeatability
Precisionunder repeatability conditions.
Repeatability conditions
Conditionswhere independent test results are obtainedwith the samemethodon identical
test items in the same laboratory by the same operator using the same equipment within short
intervals of time.
Reproducibility
Precision under reproducibility conditions.
Reproducibility conditions
Conditionswhere independent test results are obtainedwith the samemethodon identical test
items in different laboratorieswith different operators using different equipment.
Relative standard deviation (RSD)
RSD= s
i
100/
Standard deviation (s
i
)
s
i
= [Σ(x
i
–
)
2
/n]
0.5
a
AOAC INTERNATIONALMethodsCommitteeGuidelines for Validation of Biological Threat Agent Methods and/or Procedures
(
Calculationof CPOD and
dCPODValues fromQualitativeMethodCollaborativeStudyData
),
J. AOAC Int
.
94
, 1359(2011) and
Official Methods of Analysis of AOAC INTERNATIONAL
(2012) 19thEd.,
Appendix I
.
b
International Vocabulary of Metrology (VIM)—Basic and General Concepts and Associated Terms
(2008) JCGM 200:2008, Joint Committee for Guides in
Metrology (JCGM),
c
LaBudde, R.A., &Harnly, J.M. (2012)
J. AOAC Int
.
95
, 273–285.
d
ISO 5725-1-1994.
e
Official Methods of Analysis
(2012)
AppendixD
(
Guidelines for CollaborativeStudyProcedures toValidateCharacteristics of aMethodof Analysis
),AOAC
INTERNATIONAL, Gaithersburg, MD.
