(9, 10) and will not be fur- ther discussed .... of 10 IgG class-specific antisera they
studied. Recent- ly, using a panel of highly purified. IgG ... to physics and chemis-
try, e.g., milligrams per deciliter. However, in a 1970 cooperative effort,. Rowe.
Standardization A Review Charles
of Human
of Current and Shirley
B. Reimer
more
A future careful
solution
of
and Problems
of the immunoglobuof their
of these
consideration
Status
accurate
problems
calibrators,
antigens serum,
quan-
demands
a
antisera,
and
methodology. Of
all
the
serum
(Ig’s),
functionally
most
heterogeneous.
synthesizing Depending
Every
and
ogeneity of each tions reflects our fied
the
immunoglobulins
structurally,
are
second
probably
each
the
Ig’s
as such
by
tibodies
are
immunologic of our personal
are
individual “nature
antibodies, in
human specific
the
they
are
not
analysis.
animals
sis is most munodiffusion
frequently either
against
Ig’s. One hopes to the molecules
quanti-
highly
use
purified
properly
as
test of analy-
radial as
or by the kinetic (2). Also, one
analytical of variation).
precision
standardize
a heterogeneous
of between
immunoprecipitin
sis, not only must we consider must deal with the complexity men
antiby
imsug-
modifisees in-
of variations of quantitative electroim(3) and manual or automated immunoneanalysis (4), the latter technique now ca-
pable of giving 2% (coefficient To
an-
that these of interest
performed by single to quasi-equilibrium,
by Mancini et al. (1), of Fahey and McKelvey
heter-
First,
absorptions, and then some form of a precipitin is used to quantify the different subpopulations Ig’s as antigens. Currently, immunoprecipitin
creasing munoassay phelometric
be
antibody populaand nurture.” Al-
immunoprecipitin
raised
subsets of the sera are made
gested cation
the
of us may
exposure,
molecular
methodology of the human population
and
1 and analybut we speciof Ig
Biological Products and Parasitology Divisions, Bureau of Laboratories, Center for Disease Control, USPHS, U. S. Dept. of HEW, Atlanta, Ga. 30333. Based on a paper presented at the first AACC Pine Mountain (Ga.) Conference (on Diagnostic Immunochemistry), March 3, 1975; and at the Symposium on “Immunology-Interrelations with Clinical Chemistry,” Ninth International Congress on Clinical Chemistry, Toronto, July 17, 1975. Received Feb. 20, 1976; accepted Feb. 21, 1976 (reviewed before receipt).
dispersed in we certainly
the must
complex contend
plex nature of our analytical reference serum that is used parison it made
a million different kinds of Ig molecules. on our unique genetic constitution and
environmental
though
proteins,
and
Quantitation:
E. Maddison
Extreme molecular heterogeneity iins creates persistent problems titation.
Immunoglobulin
reagents. Is the human as a standard for com-
similar to the unknown serum up of a different heterogeneous
population? molecular as our
milieu called with the com-
What specificity principal
do
we really of an animal
analytical
erogeneous antibody Immunoglobulin
specimen or is molecular
know of antiserum
reactant?
It,
population. complexity.
the
too,
actual we use is a het-
Meaningful
mea-
surement requires that the specific quality of interest be selectively measured and all varieties of it be measured without bias. There are four immunologically characterized es of 1gM
have
acterized.
subclasses of IgG, two of IgA; subclassbeen described but are not well char-
In
normal
human
serum,
the
relative
amounts of the IgG subclasses 1, 2, 3, and 4 have been reported respectively as 61, 30, 5, and 4% (5). There is little if any good information regarding changes
in these
eases other antibody-forming IgG they
than
subclass must
be
autoimmune poorly, and
with
malignant transformation such as in multiple myeloma.
infectious
1 and 3 fix complement especially important
disease. subclass
to polysaccharide never
ratios in the cells,
in
other
disof
well, therefore infectious and
Subclass 2 fixes complement 4 not at all. Generally, antibody
is IgG
subclass
or
subclass
2. Antibodies
2. Rh
antibodies
to human
are
blood-clotting
factor VIII are limited to subclass 4. Genetic polymorphism produces IgG subclasses containing specific antigenic allotypes that have different distributions in different racial groups (6). Perhaps the persistence
of different
subpopulations history in the spect present case tors
to may must
Ig allotypes
in part evolution
reflects of the
different infectious disease susceptibility
in different
diseases and or resistance,
be. Ig heterogeneity caused eventually be quantitatively
a proper analytical Physical-chemical gives additional
CHEMISTRY,
man’s as the
by genetic considered
system. heterogeneity of measurement problems.
CLINICAL
human
the unique geographic races of man with re-
the 1gM
facin sample is usu-
Vol. 22, No. 5, 1976
577
ally present units, which,
as the stable 19 s pentamer however, occasionally are
of 7 s subfound free in
a 7 s form. In serum, one finds 7 s monomeric IgA and an 11 s dimeric IgA. In secretions, a further complication occurs in that dimeric IgA contains a disulfide-linked
glycoprotein,
also
in somewhat
occurs
as “free depends
secretory on the
piece.” molecular
an Ig will give immunodiffusion, phase
different
of the
bration and
forms.
other
that
they
diameters during of
act
as antibody
exist
as
soluble
19
precipitate
the
IgD
animal
occurs
in low
concentrations
per liter. membrane of
standardization
tests
that
result
technique
review. are
in immediate
used
to
the
not
of and
reaginic
low use
antiand
concentrations of a quantitative
of
simple recently
problems
of
reagent
sen-
gel techreviewed As
antisera.
standardization
problems. by Haber
Figure
1,
(12),
et al.
shows
cally the polypeptide
complex, three-dimensional backbone of pancreatic
relatively
small,
tenth
the and
many
a
amino
the evolutionary protein when mologous
CLINICAL
diagrammatifolding of the ribonuclease, a
which
specific nants,
tion lated.
molecules Depending
on
tigen ing
and sites
for those
amounts of cells
body have
the that
facts and
changing
antibody turnover speak of antibody
having lysine
overlapping hapten epitope at position
from
the
is immunized
CHEMISTRY,
animal
of two
of
specificity attached
41. Depending
species to produce
Vol. 22, No. 5, 1976
to to on
between this and the hoor individdiagnostic
population
Several munological tisera sitivity gels
(13-16).
At
eventually
stimuof an-
antibody-bindcontinuing
of antigen will usuwill produce anti-
affinity. Philosophers in the same river twice.
of antigen antibody
heterogeneity, concentrations,
changthe
of antibody-producing
IgG, that
we
to
produce antias the recogni-
cells,
rates, one probably should specificity in the singular.
years ago, specificity
to human appropriate
that
im-
changes. Certheir surfaces
that were availability
competition ally select
dot-
size
cells that specificity
the lymphocytes on the continued
highest binding we never step
of animal
and
of fit between determinants,
In view of the ing immunogen
althat
non-self determiantigens to be
the goodness and antigenic
one-
the
course
to divide
of plasma of the same
The
antibody-combining
the
molecules for by the best-fitting
establish clones body molecules
than
represent
to understand
more complex immunoIg molecule from another obtain a very heterogeneous
stimulated
with said
conformaof the
and
During
limited clones
surmole-
of antibodies
to the new as a result
antibody population prepossessing on
recognition are selected
less
different
ribo-
protein If the
subset
It is easy
response.
IgG.
or genetic differences it is used as an immunogen
protein
animal
a
be elicited produced
if one uses a much larger gen, such as an individual species, one usually will
protein,
2.5 nm, dinitrophenol
epsilon
from
a new
structure.
of human
rectangles
X
tertiary
weight
hypothetically
sites, 1.1 the same
hapten could determinants
tered
of this foreign or as non-self.
differently,
homogeneous
molecular dashed
taken
to this tional
up
preferentially
of greater
with been
folded
regions as self
munizations, the tain lymphocytes,
matter, manufacturers of immunological are expected to produce uniform diagnostic year after year. They confront very difficult
publication
antisera, different face might appear
antibody
be fur-
hypersensitivity
The the
that available Ig subset has
Specificity
578
reagents
(11).
practical products reagents
ual
as a lymas well as
as radioimmunoassay,
than This
elsewhere
serum,
of IgD (7, 8),
will
pancreatic
Haber. E.. Richards, F. F.. Spragg. J., Austen, K. F., Vallotton, N., and Page, L. B., Modifications in the heterogeneity of the antibody response. Cold Spring Harbor Symp. Quant. 8101. 32, 301 (1967)]
in human
and
of bovine
IgG,
to the surface methodological
(9, 10)
of allergy. necessitate
such
sitivity niques.
and
bound special
in this brief immunoglobulins
manifestations IgE in serum
the
reagent
The role receptor
problems
discussed IgE
bodies
ted
with
cule
standardization
The
as such,
latter has been heat-aggregated, as of a single radial immunodiffusion such a situation can give spurious
evaluate immunoglobulins B-lymphocytes presents ther
and,
structure
Based on an illustration by Marker et al. [Chem. Eng. News 45 7, 60(1967)]. The heavy circle, #{128}-DNP,represents a haptene on the lysine oup at position 41, used by Elsen et al. [Biochemistry 3, 996 (1964)]. The dotted and the dashed outlines are the size of the hypothetical antibody combining sites, 2.5 X 1.1 nm. [Reprinted with permission from the publishers and
results.
a few milligrams phocyte surface the
and, activi-
components rheumatoid fac-
tors
with
1gM
1. Three-dimensional
nuclease
complexes
complement Human
analytical
s
Fig.
mono-
factor
to IgG
and with serum cryoprecipitates.
may
the
immune
other Ig’s as mixed
particularly if the in the preparation plate. Obviously,
stops
in
rheumatoid
is, they may
quasi-equili-
is different have
radial kinetic
precipitation
Occasionally,
Ig classes
form
in single the
before
disc
valence
polymeric
ty;
the
which
the diffusion rate polymeric forms of
reaction,
and
Antigen
rarely,
disc particularly
piece,”
conformational
Because weight,
precipitin
occurs
growing.
or “secretory altered
and rarely
decided to examine the of commercially available
IgA, and 1gM at the for immunoprecipitin time
we
examined
iman-
level of senanalysis in almost
200
commercial reagents and found that only one of every three or four antisera to IgA or 1gM was class specific. More than 95% of antisera to IgG precipitated in-
appropriately
with
ago
only nodiffusion
one
specific
for
1gM,
and
specific ficity
other
than
IgG.
Three
consistently
each
producing
of the
three
IgA-although
kits
major
two
firms
six suppliers, all of whom plates that were class specific
and plied
1gM. In addition, plates that were
giving ment
easily-read in quality
Morell
three specific
found
(17)
of
that
were
produced
were for
the plates
IgG
lem
more versy
for
teins IgG
of known subclass
IgG own
single IgG
radial specific
the findings ly available relatively with With
subclass, we looked for the bias in currently available
of the aforementioned IgG class-specific more
duced
antibody
may,
authors. antisera tend
molecules
that
Currentto have
precipitate
at equilibrium, discs with 150% mass
with
the
of IgG
form single of the disc subclass
calibrator.
radial area
impro-
Given
good
units-for
a serum
pool
milli-
were made, a probthese units instead of
of
measures has given Some investigators
or in attempting
rations
that
rise to some controhave advocated re-
made
the
from
the
of the mean values obsera
of “nor-
to produce
represent
the
reference
“normal”
prepa-
population.
Ei-
one must have human serum pools representing of the normal subpopulations of interest or one try to make a single serum pool to represent the
hypothetical
“average”
patient
and
sic greater variability Some believe that
of “normal” fundamental
measurement
not
should
units
not
antisera,
yet
have
be redefined
and
of physics enough
accept
the
values. units
reliable
of biological apart
chemistry.
intrin-
from
Some
say
normative
the we do
data
in the
the other quantitation reference
important variable reagent of any Ig system is the calibrator, or comparison standard, from which the base units and
newer unfamiliar unitage to make valid comparisons between health and disease or to interpret differences caused by age, sex, and race. Most clinicians
quantity
are
have
most
very
mt.
units-i.e.,
of these human serum Ig’s; not assigned to this preparation.
normal
basic
1.
IgG, in-
mal” adults that one encounters in his own laboratory practice (25). The dependence of Ig concentration on age, sex, and race factors (26-32) creates inherent problems when reporting results as percent of mean
ther each must
1 or 2 than with subclass 3 or 4. equal masses of the latter two
by an equal
Problems
of
immunodiffusion plates and in our antisera. Generally, we confirmed
IgG subclass some antisera,
subclasses munodiffusion
presence commercial
with
Refer-
Ig’s. Recombut exclusive
Ig concentrations as “percentage value” by comparison with
tained
eight
arbitrary
recommendations acceptance
familiar (22-24).
porting normal
of 10 IgG class-specific antisera they studied. Recently, using a panel of highly purified IgG myeloma pro-
of each of these three made for the gradual
of these
Since these of general
International
of Human Immunoglobulins vial containing 100 (arbitrary)
units were
all measurements gram values were
proIgA
Organization
each
adoption
improvebias
Preparation and 1gM,
clas-
years. subclass
ence IgA,
Health
specifrom
found to measuring
decided
World
ternational mendations
of these six firms supfor human IgG as well,
single discs-a control in three
et al.
immu-
Ig classes-IgG,
1gM plates. Recently we re-tested of single radial immunodiffusion
these duce
the
years
of six firms selling single radial plates to measure the concentrations
Ig was
human
Ig’s
derived.
frequently
ume
in familiar
try,
e.g.,
Ig
units
milligrams
gave
common per
tion got
sera and a between-lab
for IgA, among
asked the Standards
wide values used
ranges obtained his own
the
low-
They then assigned pool to represent the
making problems,
thorized
use
a
and
ranges highest
the 1.36-
used, with
1gM.
or
fold
for
Encouraged supported freeze-dried
IgG,
1.17-fold
for
IgA,
by this result, the by an expert committee human
serum
pool
and
1.31-fold
authors (20,
available
and for
of the study, 21), made this generally
as
mass
familiar
any change difficult. another expert committee
of conversion
the
to mass probably
prove
between the lowest were greatly improved:
more
and some even believe ranges in these units,
factors
Recognizing (23)
obtained
from
authe
Ig content
of the
WHO
Interna-
tional Reference Preparation is accurately-that is, truly-defined in international units with a betweenvial CV of less than 1%, reflecting the ease of reproducibility in filling vials. However, the conversion
concentrations of IgG, IgA, and 1gM, and distributed it as a comparison material to each of the cooperating investigators. When all laboratories used this preparation as a common arbitrary reference standard, the of relative means values obtained
the
data of Rowe et al. (19) to relate the two of measurement: 80.4 g IgG, 14.2 tg of IgA, tg of 1gM are equivalent to 1.00 international
factors
arbitrary unknown
to
dimensions, true normative
unit. Categorically,
agreement this effort
Institutes of Biological process and freeze-dry
they
accustomed
volume know
thereby these published systems or 8.47
by experts when standard calibra-
for 1gM! To improve the organizers of
serum. to this
chemisin a 1970
between
become
unit
per that
For the same samples, they of 2.2-fold for IgG, 3.2-fold
British National and Control to
pool of human potency units
and
However,
been to vol-
et al. (18, 19) found that the of six coded serum sam-
antisera. range
and 5.0-fold laboratories,
of mass
to physics
deciliter.
unacceptably
est and the highest each independently
have
as a ratio
cooperative effort, Rowe means of Ig concentrations ples
concentrations
expressed
that
units will
both
bitrary
with
and of
areas, will
Ig should the WHO
results
carefully
CLINICAL
units)
from
measured Reference
by
calibrated
CHEMISTRY,
the
same
imso
different different the units
comparison Preparation
supply secondary WHO preparation and
to
present,
times, or from irrespective of
usually against the
international
uncertainty efforts
At
obtained
at different be valid
standard
Manufacturers calibrated
to much further
accuracy.
always be International
a secondary
to it. dards
subject
precision
comparisons
geographic investigators
are change
relative stan(in arsecondary
Vol. 22, No. 5, 1976
579
standard quantified
also calibrated mass of each
more familiar d’Unites (SI). tion
of mass
units Many units.
with class
a weighed of purified
of the errors
of Ig may
correctly determined not completely pure,
because the or, commonly,
nologically
all subsets
class.
represent
The
purified
tigenically become
aggregated,
behave
differently
does
the
manufacturer protein for
for
in
native
the
subclass
and
other
In
May
as already
ciency Testing 125 laboratories
the
U.
(33).
Three
cates coded
of the same normal macroglobulinemic
were
and
SI
(mass
that
Less
than
5%
Behringwerkea
86.8
16.8
a70
Helenaa
11.3
8.68
Hylanda
75.2 86.8
20.9
7.74
Kallestada
87.0
18.0
5.65
Meloya
15.0
7.70
Milesa
81.9 81.6
Pt izera
87.0
17.3
8.56
Technicona
87.1
16.8
8.67
et al.
#{176}Data from
manufacturers’
package
literature.
of common, house”
dupli-
IgG and commercial radial
have
permitted
arbitrary reference
tributed
calibrator preparations
to clinical
gested
for
dior
laboratories
that
we are
future
“in dis-
measurements traditionally
dards
dealt
with
research.
About
2 years
National Bureau of Standards Clinical Chemistry entitled: Has Come,” wherein he sug-
now
meaningful Although has
to adjust their which, in turn, are
users.
Considerations
ago, J. Paul Cali of our wrote an editorial in “An Idea Whose Time
im-
results in either (arbitrary) units of these
6.00
et al.
(36)
tests
single
would
(27)
10.0
Pilgrim
and one was a greatly supra-
subnormal used
to report their international
units).
coded
serum with
purchased
plates
these laboratories mensional system,
were
of 1gM and laboratories
standards
munodiffusion
two
9.2%) 3.06
Profi-
the performance quantitative Ig
sent;
(CV
94.0
than
volume shown in and
7.9%)
‘43.1
&30
(29)
suppliers factors
Licensure
human serum
normal concentration IgA. Almost all tested reference
S. CDC
(CV
7.5%)
59.5
and
1gM
47
16.5
may
These
to mass-per-unit materials, as
Branch evaluated performing samples
discussed.
IgA 14.2
85.0
Cejka
If the
explain why reagent different conversion
units calibration
1973,
matrix.
lgG
80.4 (CV
Buckley Dorsey
have
the presence of antibody to would make calibration bias arise if class-specific antisera
selectivity,
relating international in each of their Table 1.
an-
may
et al.
(19,23)
Ig
system
a serum
Rowe
the same purified monoclonal that he used as an immunogen
reasons can give somewhat
usually
was immu-
reason,
calibration in
to produce his antiserum, idiotypic determinants likely. Bias could also had
other
Source of information
in-
become or
some
molecule
used calibration
have
purification
or,
been
preparation it may not
may
during
have
of a heterogeneous
preparation
altered
Table 1. Number of Micrograms of Immunoglobulins Corresponding to 1.00 International Unit
Syst#{232}me International can arise in the calibra-
mass
The
or otherwise Ig using the
able
to reach
an
in clinical National
our much
era
of more
chemistry (34). Bureau of Stan-
simpler
phenomena
than
chose to use the WHO international units, which with normal sera gave an 11% CV for IgG, a 7% CV for IgA, and a 20% CV for 1gM. The corresponding variation of results from the majority of independent
are usually encountered in biology and medicine, they have been able effectively to generalize the intellectual process that they use for standardizing physical and chemical analytical systems. Table 2
laboratories
reporting
of methods
and
lists Cali’s requirements leading to meaningful
CV for variability serum. can
and
IgA,
in SI units
materials 32% found
was Ig proficiency
Pathologists
(personal results concerned service,
from
was
by the
recently
given
communication, these laboratories,
Pierre
mentioned
results earlier,
general
or nonacceptance
acceptance
results
CLINICAL
clearly
available here
in was
for Ig measurement, technology transfer
commonly preparation, 580
IgG,
College
21%
quirement,
more
CV’s
Keitges). The were generally
used
1970, available.
this case to produce demonstrates
world
experts
before the Regardless
of
history more the
value
Vol. 22, No. 5, 1976
for
that is, whether chemists, we are
we should comfortable
call
that
number base ber.
of effecuniform of
a
WHO as a
Actually
deal of discussion should be used
most
We
of science,
has
for feel
the
even physical
and,
as chemists,
most a great units
consist
with
as in-
WHO Expert Those who
secure, with the sciences, should
quantity
dimensions
comfortable
that
been
use the SI units that, with or the arbitrary
measurements expresses
process first re-
which base measurement-
of two
and
that provides the dimensions is some subtle psychology
preference try.
is one
there
recently about immunoglobulin
perhaps to the
that unit There
units,
units recommended by the on Biological Standardization.
feel comfortable, units customary
of international
reference preparation, the by reagent manufacturers
CHEMISTRY.
ob-
of base
to neglect.
ternational Committee
WHO
for a standardization measurement. The
acceptance
of us tend
of Ameri-
concordant
W. which
of the
tained three years Reference Preparation
clinical
a variety
for
with providing ordinary routine diagnostic were in much better agreement than were the
previously
units tive
using CV
CV for 1gM. Somewhat for the macroglobulinemic testing
has
and 17%
the
base re-
parts:
a
associated
for that involved
numin our
of physics
and
the
of the
unity
units
that
notion
we prefer
base
chemis-
Table 2. Standardization
Requirements Measurements (34)
Meaningful 1. A rational
of BASE
system
2. Certified STANDARD 3. Accurate 5. Periodic
reference
performed
not
delude
and
operations.
metric
ourselves
mensional
by
scales. our
Because
best
units
SI,
we
terms
accept
cannot
uncritically
are associated
as correct
these tract
units. If we had a way to stoichiometrically all of the IgG from a unit volume of serum, other
components,
a balance to weigh swer. Instead, we
and,
problems
quate
general
reference
unavailability
materials,
ear-
In
experts
priate
base
that
who
are
the
nating
units
“standard”
dard”
different
as a synonym
adere-
adequate
reference
described
in appro-
certifying systems
lect lar
a native to
the sine ity-stability
qua
ity during native a thawed, terest
than the word “precise”-denoting ibility-to characterize reference sis. Knowledge of the biochemical
nevertheless,
dard)
Characterization
analytical
by
use
use
using
as a reference. the
the
WHO
unfor-
certified proper
tion
for
this
is possible.
type
to been
consider frozen
for
as and of inmen-
on Biological
Ig quantitauniversal proposed
standardization
acby
Standards
of Human A possible
ods
(say
Imsoluprob-
single
specificity
into
values
if ever,
will
for
also
providing
tical
of
stable use allow
of a us to
and
immuno-
with use of the same antiseand base units, give signifwith
would
be
the
same
specimens?
to experimentally
A deter-
select the most precise arbitrary reference method correction factors to bring
obtained
with
the
less
precise
first
three requirements perfectionist type
are best of scientist.
of results for the clinical patient is most fact, the patient is almost an annoyance of development of standards. The essence rect With
possible
analysis
of and the
method
agreement.
Cali’s compulsive,
three
dilution which is of many
it be
Methods
immunodiffusion
mine and authoritatively these methods as the develop appropriate mean
a
(valid) results by several methods. to do if two apparently useful meth-
results
solution
of
is itself
Materials. Hopefully, Reference Material will
analysis), preparations,
different
practical
situa-
problem. Unfortunately, in if any, “absolute” or “defini-
without
radial
nephelometric ra, reference icantly
is stabilstabil-
made in precision (re(conformity to a stan-
Preparation and 1gM.
of biological
bioto secourse,
the molecules As previously
process
Committee Reference IgG, IgA,
each
quantitation
Reference
Reference Standard
obtain the same But what is one
simiOf
standard particularly,
is impossible that has
substances
which,
there has not been base units (mt. units)
Expert
for the WHO munoglobulins
in
molecular
for
Rarely,
accurate
biological
to standardlegalistically Standards.”
analyses.
to specify
“stan-
is as analytically as
simple
used
the
of its accuracy. Imof great specificity
proven
of the
antisera
standardization there are few,
word
reference material, generally try
improvement was and in accuracy of this
be
of
reproducof analyof any
chemical
non for any material during storage and,
tion. Unfortunately, ceptance of the
must
use
mere methods specificity
method is crucial to assessment munoprecipitin analysis is capable tion.
the
or truth-rather
desig-
or freeze-dried; however, must be undenatured.
tioned, great producibility)
note validity
alunits
notice
that
shipment. It whole serum
requirement,
confidence,
for
“specification”
of interest
improved
Also
a standard of standardization
thing
third
with
here
for
preparation
the
mean
to other
aware that a It is to be the “true”
of us.
tunately, is often done when attempting ize diagnostic tests by formulating worded documents called “Performance When logical
compelled
anything
to most
from for
for
is reserved
preparation
is quite
felt
units
tive” methods of analysis such as the isotope mass spectrometry method for calcium (35), proposed as a model for the standardization
quantitatively acceptable
word a material
This
establish
If a user SI
“accurate”-denoting
which,
second
this
Cali’s
word
group
that
in
the value of the mean in international always be 100, by definition.
difficult biology
of
large.
value
a conversion factor, he should be error may accompany this value. that, in time, we would approach
quirement. Note his use of the word “certified” here, which implies a consensus by some authoritative materials
estimate of each compodeviation as derived consensus. The indeterminacy
of
it on
of
Cali’s
than large hoped
of varia-
would be quite the base units of
mean
quite
mean
an
its standard
and
be
coefficient
though would
correct anmethods
discussed units. standardiza-
the
and
the
value
exfree
put
might
the
by
comuse
there would units of activfor this uni-
diwith
loss,
have the comparison
analysis that we for arbitrary base of most biological
is the
standard
without
it, we would must use the
of immunoprecipitin lier-hence the need Probably the crux tion
that
use
be represented
each
would
ac-
the
cept
it from
numbers
must
familiar
we intuitively
of the the
for
and that
we
for
system
the SI to give nent of interest from experiment
However,
desire
units
One
for
to the analytical balance that reduce to operations
with
of base
vial filling, which unitage would use
continued
could
here
are
systems
preparation.
tion obtained for small. The second
of quality
fundamentally relate volume measurements
two
tage
tests
TESTING
PROFICIENCY
control
MATERIALS
and
is to use
plex
of analysis
METHODS
METHODS
lem
arbitrary unitage; by decree or definition be, say, 100 arbitrary (or international) ity in each vial; the confidence interval
for measurements
REFERENCE
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CHEMISTRY,
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corunits. pracfield 581
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sitive, methods, we
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reference
by
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we
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ance,
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field methods and In an evaluation of consensus of ex-
methodology
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CurPro-
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