Comparisonof Resultsfrom the Du Pont “ACA”and
Technicon“SMA 12/60”
James 0. Westgard and Brenda L. Lahmeyer
The Du Pont “Automatic Clinical Analyzer” (ACA)
and the Technicon “SMA 12/60” were compared
as to precision, range of linearity, and results for
sera from patients. Precision of the ACA was equal
to or better than that of the SMA 12/60 for all determinations except SGOT in the normal range.
The ACA showed a wider range of linearity for
BUN, total protein, LDH, alkaline phosphatase,
SGOT, and bilirubin, and equal linear ranges for
glucose and albumin. Patient’s sera comparisons
showed differences for glucose in uremic sera.
Albumin values from the ACA did not compare well
with those by HABA dye method from the SMA
12/60, but did compare well with values obtained
by electrophoresis and by a bromcresol green
method adapted to the SMA 12/60. Bilirubin values
from the ACA were higher than those from the
SMA 12/60. Comparable results were obtained for
the enzyme determinations when the SMA 12/60
was calibrated in the same units as the ACA.
Additional Keyphrases
clinical
laboratory
values
performance
of automated
systems
compared
ESKALAB
#{149} glucose
in uremic serum
#{149} electrophoresis
on cellulose acetate
.
precision of secondary analytical
methods
.
AutoAnalyzer
.
DSA
560
emergency
service
The “Automatic
Clinical Analyzer”
(AcA;
E. I.
du Pont de Nemours
and Co., Inc., Wilmington,
Del. 19898) has been in routine service for several
months in our clinical laboratory.
During this time,
we have evaluated
the performance
of the ACA.
Previous
performance
studies
on prototype
instruments
have been reported
by Evenson
(1),
and Perry et al. (2). These studies included precision, linearity,
and recovery,
and some comparisons with other methods.
Our results
represent
the performance
of the
production
model ACA as used in routine service.
In our laboratory,
the ACA performs single-request
and emergency
analyses. Used in this manner, the
From the Department
of Medicine and the Clinical Laboratories, University of Wisconsin Center for Health Sciences, Madison, Wis. 53706.
Presented at the 23rd National Meeting of the AACC, Seattle,
Wash., August 8-13, 1971.
Received Nov. 11, 1971; accepted Jan. 3, 1972.
340
CLINICAL
CHEMISTRY, Vol. 18, No. 4, 1972
analytical
capability
of the ACA complements
the
screening capability of the “SMA 12/60” (Technicon
Corp., Tarrytown,
N.Y. 10591). Glucose,
BUN,’
total
protein,
albumin,
alkaline
phosphatase,
LDH, and SGOT (e.g.) may be measured
by either
or both instruments
in the course of patient treatment. Results for these analyses
are reported
via
the laboratory
computer
system and are not distinguished
as to the method
or instrument
used.
To be able to use the ACA and SMA 12/60 in this
manner,
we had to evaluate
the comparability
of
performance.
The evaluation
presented
here emphasizes the comparison
with the SMA 12/60 and
includes study of precision, range of linearity,
and
comparison
of analytical
values between these two
instruments.
Materials and Methods
ACA:
Methods used with the ACA include glucose
by hexokinase,
BUN
by a urease-glutamic
dehydrogenase
coupled reaction,
alkaline phosphatase
with p-nitrophenyl
phosphate
as substrate,
SGOT
by a modified Karmen procedure,
LDH by a modified Wacker procedure,
total protein by biuret reaction, albumin by BCG dye binding, and bilirubin by
differential
absorption
at two wavelengths.
SMA 12/60:
The instrument
used was a standard
survey model, originally
with colorimetric
assays
for SGOT and LDH, but updated
to ultraviolet
methods
during the course of this work. Albumin
was initially
determined
by the standard
HABA
dye method, but this method was replaced with a
BCG method
in later studies.
Details
of the BCG
method
are available
from this laboratory.
The
SMA 12/60 used Harleco
reagents
(Harleco,
60th
St. and Woodland
Ave., Philadelphia,
Pa. 19143)
and was standardized
with Technicon
reference
sera for which set point values were established
in
our laboratory.
1 Nonstandard
abbreviations
used: STJN, urea nitrogen; SOOT,
serum glutamic-oxaloacetic
transaminase
(L-aspartate : 2-oxoglutarate aminotransferase,
EC 2.6.1.1); LDH, lactate dehydrogenase
(i.-lactate: NAD oxidoreductase,
EC 1.1.1.27); alkaline phosphatase (orthophosphoric
acid monester
phosphohydrolase,
EC
3.1.3.1); cv, coefficient of variation (relative standard deviation);
BCG, bromcresol
green; HABA, 2-(4’-hydroxyazobenzene)
benzoic
acid.
“AutoAnalyzer”
(Technicon):
Glucose was determined by use of an o-toluidine
procedure
(3).
“DSA 560”
(Beckman
Instruments,
2500 Harbor
Blvd., Fullerton,
Calif. 92634) : Albumin was determined with a modified Beckman
BCG procedure.
“ESKALAB
Clinical
Chemistry
System”
(Smith,
Kline & French Laboratories,
3400 Hiliview Ave.,
Palo Alto, Calif. 94306): Glucose is determined
by a
hexokinase
procedure
and SOOT by a modified
Henry procedure.
Electrophoresis
on. cellulose acetate: A Beckman
“Microzone”
system was used. The electrophoretic
pattern was scanned with a Beckman
“Analytrol”
densitometer,
and the areas under the peaks were
integrated.
Albumin was calculated
from the peak
areas and the total protein concentration
was estimated
by ref ractometric
measurement
(Model
10400 TS meter, temperature
compensated;
American Optical Corp., Eggert and Sugar Rds., Buffalo,
N.Y. 14215).
Results and Discussion
Precision
Day-to-day
precision
was studied
with use of
commercial
lyophilized
control products.
Table 1
shows the average relative standard
deviations
for
results obtained with the ACA and SMA 12/60 during
a four-month
period. F values (4) are also tabulated,
and numbers
greater
than 2.0 indicate
that the
differences
in precision are statistically
significant
(at P = 0.05, or 95% confidence
limits). For the
normal control serum, the precision
of the ACA is
better than that of the SMA 12/60 for BUN and
albumin
and worse for SOOT. For the control with
abnormal
concentrations,
the precision of the ACA
is better
for LDH,
albumin,
and bilirubin.
For
constituents
other than these, the differences
in
precision are not statistically
significant.
Discussion.
The somewhat
poorer precision
for
soot is due to the low sensitivity
of that particular
reaction, a difficulty compounded
by the short time
between
the two absorption
measurements
on
the ACA (17.1 s). The sample size on the method
has been maximized
(0.5 ml), but even this large
sample does not adequately
compensate
for the
low sensitivity
of the reaction.
The precision data from the Wisconsin
Society
of Pathology
survey should provide an unbiased
comparison,
because identical
pools were used in
both studies. However, the values from this survey
may be somewhat
optimistic,
as suggested
by
Laessig and Schwartz
(5). In this study, the identical pools were submitted
as “blind” controls in the
performance
survey conducted
by the Wisconsin
State Laboratory
of Hygiene.
This blind study
showed
that some laboratories
reported
results
that averaged greater than two standard
deviations
from their own means
(interpreting
their data
based on their own averages and standard
deviations for each method).
Range of Linearity
Experiments
were conducted
to assess the range
of linearity
on the ACA by using a series of aqueous
standards
for glucose and BUN, and dilutions of patient samples
with supranormal
values for the
Table 1. Comparison of the Precision of the Technicon SMA 12/60 and the Du Pont ACA
Determination
Glucose
BUN
Alkaline phosphatase
SGOT
LDH
Total protein
Albumin
Bilirubin
Concentration
normal
225mg/100 ml
normal
50mg/100 ml
normal
3X normal
normal
3X normal
normal
2X normal
normal
6 g/100 ml
normal
3 g/100 ml
normal
4 mg/100
ml
Relative standard deviation (CV), %
Av for 4 months
ACA
12/60
12/60
U. Wis. Hosp.
U. Wis. Hosp.
WSP surveya
2.6
1.6
2.3
1.6
5.4
3.2
8.6
3.1
5.1
1.6
1.6
1.8
1.5
1.8
3.9
2.5
3.8
2.2
3.9
2.8
6.0
3.8
5.4
4.2
4.4
2.8
2.7
2.6
3.6
3.4
2.5
2.14
1.89
1.71
3.6
1.9
2.88
2.44
2.45
3.06
1.41
5.8
4.3
4.9
1.23
1.15
1.81
3.4
5.6
3.5
1.6
2.1
2.6
6.3
3.0
4.8
5.9
4.5
3.4
F values
vs 12/60
vs 12/60
U. Wis. Hosp.
WSP survey
1.41
2.54
1.84
1.34
3.06
3.06
2.09
3.08
0.83
1.21
4.79
1.00
3.57
1.36
3.00
2.78
2.61
5.57
3.24
5.76
1.51
a These data represent
the average precision for 17 other SMA 12/60’s, as calculated for monthly data obtained from the survey
conducted by the Wisconsin Society of Pathologists. The control products used in this survey are the same products and lot numbers
as those used in our ACA precision studies, but are different from the control products used in our SMA 12/60 studies.
CLINICAL
CHEMISTRY, Vol. 18, No. 4, 1972 341
other determinations
(Table 2). For the SMA 12/60,
experimental
data confirmed
full-scale
linearity
for all tests except albumin,
for which linearity
was tested only to 6.5 g/100 ml. For albumin and
glucose,
comparable
ranges of linearity
are observed; for total protein and LDH, the ACA ranges
are about
25% greater;
and for BUN, alkaline
phosphatase,
SOOT, and bilirubin,
the ACA ranges
are about two to three times those of the SMA
12/60.
Discussion.
The ranges of linearity
for the ACA
methods
are generally
greater than those for the
SMA 12/60.
However,
the linearity
of the enzyme
methods initially had to be interpreted
with great
care. For enzymatic
methods, as substrate
becomes
depleted,
artifactually
low rates are measured.
Linearity
curves over a wide range of enzyme
activities
actually
show a maximum,
with lower
values being obtained
beyond a certain activity.
This problem
was eliminated
by an instrument
modification
that uses a final absolute absorbance
value to determine
whether
substrate
has been
depleted.
An absorbance
limit is set, and when
this limit is exceeded,
an error signal is printed
out. Thus, the error signal indicates
those samples
that must be diluted and remeasured.
Table 2. Comparison of the Range of Linearity
of the Technicon SMA 12/60 and the Du Pont ACA
Determination
mg/100 ml
mg/100 ml
Glucose
BUN
Alkaline
Unit
phosphatase
U/dI
SGOT
LDH
Total protein
U/liter
U/liter
g/100 ml
Albumin
Bilirubin
g/lOOml
mg7lOOml
Upper limit of
linearity
ACA
12/60
500
100
500
200
40
100
300
600
10
550
800
12
6.5
10
6.5
30
Table 3. ACA Calibration Settings
Determination
Glucose
BUN
Alkaline phosphatase
SGOT
LDH
Total protein
Albumin
Bilirubin
Scale
factor
Total zero offset
49.2
-16 mg/ba ml
661.2
-1.4 mg/100 ml
489.2
606.4
758.0
697.2
None
-2 U/liter
None
-3.96 g/100 ml
11?.8
530.0
-0.20 g/100 ml
-0.50 mg/100 ml
Comparison of Values
Before results for patients’
sera were compared
for the different
instruments,
the calibrations
of
several ACA methods
were checked.
For glucose
and BUN, aqueous standards
were used to confirm
the ACA calibration-scale
factors. For total protein,
commercial
lyophilized
products
from
several
different manufacturers
were assayed to check the
scale factor. For albumin,
data from electrophoretic analyses
of samples from patients were used
to adjust the scale factor. For bilirubin, adjustment
in the scale factor was based on assay of “Versatol” control products
(General
Diagnostics,
Division of Warner-Lambert
Co., Morris Plains, N. J.
07950). For the enzymes, the scale factors recommended by Du Pont were used without
any adjustment.
Table
3 summarizes
the calibration
settings for our ACA.
Each serum sample to be compared
was divided
and a single analysis
performed
by each instrument. The resulting
data were subjected
to leastsquares analysis to determine
the slope and intercept. The data points were plotted and the leastsquares line was drawn by computer.
We chose
this statistical
method
of presenting
the data
because it emphasizes
the type of error between
methods:
If results by the two methods
agreed
perfectly,
the slope would be 1 and the intercepts
0. Slope values
different
from 1 may indicate
proportional
errors, such as differences
in calibration settings.
Intercept
values different
from 0
342
CLINICAL CHEMISTRY,
Vol.18,No. 4,1972
may indicate constant
or blank errors, such as zero
settings
on the instruments
or blanking
of the
chemical methods.
The comparison
data were also subjected
to
“paired data analysis”
(4) to determine
the average values, bias between
methods,
standard
deviation of the difference between methods,
and the
i-value. These values as well as correlation
coefficients are presented
in Table 4. For the number of
samples
included
in the comparison
studies,
Ivalues less than about 2.0 indicate that the differences between methods are not statistically
significant (95% confidence level).
Glucose. In comparing
glucose results, we studied
two different patient
populations.
Figure 1 shows
comparisons
for 132 patients
with normal BUN’S.
The slope value indicates
that the calibration
settings are in good agreement.
The intercept
values
suggest a blank error, i.e., the reducing method on
the SMA 12/60 gives a value of 4.2 mg/100
ml
when the enzymatic
method
on the ACA gives a
value of zero. Statistical
analysis
of the paired
data (Table 4) gave a bias of 5.1 mg/100 ml and
a standard
deviation
of 7.2 mg/100 ml, yielding a
i-value of 8.027, which shows that the bias between
methods is statistically
significant
(95% confidence
level).
To determine
if this difference
was the result
of the greater specificity
of the enzymatic
method
as compared
to the reducing
method
of the SMA
Table 4. Statistical Analysis of Comparison Data from Patients (ACA vs. Method Listed)
No.
Determination
Comparison
Glucose
BUN
Alkaline
phosphatase
LDH
SGOT
Total protein
Albumin
Bilirubin
E
em-
method
samples
Av value
for ACA
132
135.83
compared
12/60 neocuproine
manual hexokinase
o.toluidine by AA
12/60 (5-150 mg/lOU ml)
12/60 (5-50 mg/bOOml)
12/60 (U/liter)
12/60 (U/dl)
12/60 (color, U/liter)
12/60 (uv, U/liter)
12/60 (color, U/liter)
12/60 (uv, U/liter)
12/60
12/60 (HABA)
DSA (BCG)
Electrophoresis
96
92
88
98
150
68
SD
between
methods
methods
138.78
118.78
45.23
18.02
14.02
80
111
12.51
274.95
262.63
49.95
103
65.42
108
108
127
78
6.83
3.26
3.21
3.12
12/60 (BCG)
53
3.05
12/60
77
0.920
153
Bias
between
t-value
5.133
1.375
7.234
7.211
8.027
1.868
1.244
7.349
1.530
1.330
0.260
93.573
0.203
2.746
0.812
69.824
0.913
24.107
12.616
30.488
6.867
0.317
0.463
4.542
3.170
16.413
24.614
3.487
27.973
0.359
0.031
0.692
0.011
0.035
0.047
0.100
1.832
12.630
2.472
9.667
0.531
1.002
15.541
0.151
0.787
0.204
0.191
0.214
1.496
1.746
4.100
Correl.
coeff.
0.996
0.997
0.993
0.997
0.998
0.987
0.983
0.994
0.994
0.974
0.994
0.955
0.957
0.980
0.957
0.975
0.977
Table 5. Glucose Values Compared for Sera
with Supranormal BUN’s
P05,01. ,.Ilh ,lon,,Ol BUN.
132 Sp.cnins.
Slop. 0.993
IVN,copt.
V
, 5
Glucose (mg/100 ml) as determined
by
Du Pont
Hexokinase
SMA 12/60
ACA
(ESKALAB)
0
BUN,
mg/100 ml
E
40
50
50
50
50
205
139
100
97
92
187
128
100
79
85
181
121
104
81
85
60
60
60
60
100
100
105
109
144
74
91
95
100
142
79
93
97
91
148
95
95
153
82
83
140
85
87
142
132
110
108
144
124
127
140
107
116
180
203
132
86
95
153
172
115
92
101
160
174
116
Av
127.4
112.1
114.0
0
4
C.)
4
C
0
0.
0-
I
Technicon
2ll
SMA
I
12/60
Fig. 1. Glucose results compared:
(mg/IOOmi)
ACA VS. SMA
12/60
12/60, we compared
the results from the ACA to
those obtained
by a manual hexokinase
procedure
and by a single-channel
o-toluidine
method.
For
both the hexokinase
and o-toluidine
comparisons,
the i-values are less than 2.0; thus, the observed
differences are not statistically
significant.
The specificities
of the methods
were further
investigated
by comparing
samples that had BUN
concentrations
ranging
from 40 to 140 mg/100
ml. For the 20 uremic samples studied,
Table 5
shows results for glucose as determined
by the
SMA
12/60, ACA, and manual hexokinase
procedure.
The differences
between
methods
are fairly illustrated
br the average
values, which were 127.4
mg/100
ml for the SMA 12/60, 112.1 for the ACA,
and 114;0 for the manual hexokinase
procedure.
Thus, the highest
(and probably
least accurate)
values were observed for sera from uremic patients
if glucose was determined
by the nonspecific
reducing method on the SMA 12/60.
60
70
70
80
90
100
1
120
130
BUN. In Figure
2, results are compared
for 88
specimens
with values ranging from 5 to 150 mg/
100 ml. Analysis of the paired data gave a bias
of 1.33 mg/100 ml and a highly significant
t-value
of 4.542. A second comparison
study was conducted
with 98 specimens that had BUN values of less than
50 mg/100
ml (Figure 3). Analysis
of the paired
data again showed a statistically
significant
differCLINICAL
CHEMISTRY,
Vol. 18, No. 4, 1972 343
ence (i-value, 3.170). However
the bias was only
0.260 mg/100
ml and the standard
deviation
between methods was only 0.81 mg/100 ml. For the
98 samples,
the largest
difference
observed
was
2 mg/100 ml, and only two samples
showed this
discrepancy.
Thus, for practical
purposes,
results
from the methods agreed acceptably.
Alkaline
phosphatase.
Comparisons
for 151
specimens
are shown in Figure 4. The low value
of 0.132 for the slope shows the relationship
between units on the ACA (U/dl)
and units on the
SMA 12/60
(U/liter).2
Normal
range for the ACA
method is indicated
on the Y axis as extending
to
about 10 U/dl, thus the comparison
data covers
a range of five times normal, and good agreement
151.clm.n.,
ln$ocspl.
0.975
#{149}
Q_ii
IOU-
8
E
30-
4
so0
0.
30-
3)
So
110
Technicon SMA 12/60
Fig. 2. BUN
results compared:
range 0-150 mg/100 ml
so-
51.1
V
4
C.)
4
8
20-
0.
0-
I
,i
Technicon
Fig.
I
310
SMA 12/60
(U/lIfer)
4. Alkaline phosphatase results compared:
12/60(U/liter)
ACA
Vs.
BUN
89 SpicImens #{149}
Slop.
Inl.rc,pts
Y 2i
E
0.132
40-
s
150-
Sop.
V-0l4,
ACA
(mg/IOOcnO
vs. sr.t
12/60, for
BUN
99 SpecImens, Slop. 0.989
mIecepis
#{149}
V 21g.
40E
0
0
30-
between methods
is apparent
up to at least three
times normal.
The difference in units makes it difficult to use
results from the ACA and SMA 12/60 interchangeably in patient
treatment,
even though
there is
linear correlation
between
methods
(correlation
coefficient
=
0.987, Table 4). To eliminate
conf usion that may result when two different units are
used, we calibrated
the SMA 12/60 in U/dl and
then made further
comparison
studies. As shown
in Figure 5, the values approach
a one-to-one
relationship.
Paired data analysis
gave a t-value of
1.832 (Table 4).
SOOT. The wide scatter
in the low range (Figure
6) indicates
the poor agreement
between
results
by the ultraviolet
method
that is used with the
ACA and the colorimetric
method that is used with
the SMA 12/60. We also compared
results from a
manual two-point
kinetic assay, as performed
with
the ESKALAB system. These data (Figure 7) show
considerably
less scatter
around
the upper limit
of normal. After this study, an ultraviolet
method
for SOOT was installed
on the SMA 12/60, and an
4
C)
Aikailn. Phosphotass
Ce Sp.oIm...,
Slop.
40-
0.
h,tw..$:
0.950
‘r04,X-0.4
10-
4
C)
#{163}
303
Technicon SMA 12/60
Fig. 3. BUN results compared:
range 0-50 mg/100 ml
ACA
403
(mg/iOOmi)
vs.
S?viA
2 Technicon’s
enzyme units are given as mU/mI,
equivalent
to U/liter. For the data in Figures 4, 6,
SMA 12/60 results are numerically
equal to the values
the chart paper. For the data in Figures 8 and 10, the
values are not equal to standard
Technicon values
differences in calibration.
344 CLINICAL CHEMISTRY,
20-
JO
Vol.18,No. 4,1972
12/60,
for
and are
and 9, the
read from
numerical
because of
I
JO
Technicon SMA 12/60
Fig. 5. Alkaline
phosphatase
sai 12/60(U/dl)
results
(U/dl)
compared:
ACA
vs.
SOOT
III Sp.cSn.,s,
200-
SGOT
200Slop.
Yi,
Iot.,CSpI*
0.047
i1.f
S
S
4
C.)
4
4
C)
4
100-
0
0.
icc,-
C
0-
I
I
colorimetrlc
Technicon SMA 12/60,
Fig. 6.
results
SOOT
colorimetric
compared:
ACA
0-
410
I
vs.
I
I
0
(U/liter)
Technicon
SMA
12/60
method
Fig. 8.
method
I
100
SMA
200
2/60,
results compared:
SGOT
200-
UV (U/liter)
vs.
ACA
SMA
12/60 uv
LOll
IbI
Spscb..s #{149}
Slop. 1.093
I.t#{149},cep$s.
05,9.
0J2
800-
600-
-
-
4
0
4
100-
I
0-
I
0
I
I
I
I
200
I
I
I
I
000
400
000
Technicon SMA 12/60,Colorimetric
IOU
Eskolob, 2 point UV Kinetic
I
0
(U/liter)
Fig.7. SOOT results compared: ACA vs. ESKALAB
additional
104 samples were compared
(Figure 8,
where the units on the SMA 12/60 are U/liter, based
on our calibration
of the instrument).
Paired-data
analysis gave at value of 0.531 (Table 4).
LDH. Figure
9 compares results between the ACA
and the colorimetric
method
on the SMA 12/60.
The normal range for the ACA method is indicated
on the Y axis as extending
to about 200 U/liter,
and good correlation
is observed
up to at least
three times normal.
When the SOOT method
on
the SMA 12/60 was changed, an ultraviolet
channel
was also installed for LDH and calibrated
in U/liter.
Comparisons
between the ACA and the SMA 12/60
ultraviolet
method are shown in Figure 10. The I
value was 2.472 (Table 4), which shows the difference between
methods
to be statistically
significant at the 95% confidence
level. However,
the
data in Figure
10 show that good agreement
is
obtained
at about 200 U/liter
units, which is the
upper limit of normal and therefore
the most critical region for instrument
agreement.
Only two of
the 80 samples differed by more than 10%. We
therefore
considered
the agreement
between methods to be acceptable
for our purposes.
Fig. 9. LDH results compared:
metric method
I Sp.clm.n.,
-
a,
Slop.
‘1-24.8,
600-
ACA
vs.
(U/liter)
12/60 colon-
SMA
1.080
0 22.9
-
4
C.)
400-
4
C
-
200-
I
I
0
Technicon
Fig. 10.
method
LDH
I
I
SMA
I
I
400
200
600
2/60,
results compared:
UV
ACA
(U/liter)
vs.
SMA
12/60 uv
Total protein. Comparisons
on 108 samples are
shown in Figure 11. A t value of 1.002 was calculated (Table 4).
Albumin.
Figure 12 shows the poor agreement
between results obtained
by the HABA dye method
on the SMA 12/60 and those by the BCO method on
the ACA. The differences
between
methods
could
CLINICAL CHEMISTRY,
Vol.18,No. 4.1972 345
Total Protein
lOS Spedm.,.,
Slop. 1.044
l.t.c.p$o.
Y93,
0
10.0-
6
6.0-
__
8.0-
0
2
a.
00.13.0
0.I4
E
5.0-
0
0
4.0-
4
0
-
3.0-
a,
4
C)
4
Int.nc.plo
4.0-
4
2.0-
0.
0
2.0-
1.0-
0.0-
0.0
2.0
4.0
6.0
Technicon SMA 12/60
e.o
Alb,inh,
105 Sp.clm.ns.
I.t.no.pls
.
5bops
I
I
vs.
SMA
I
I
2.0
Beckman
ACA
I
1.0
I
3.0
DSA
4.0
5.0
(g/lOOml)
Fig. 13. Albumin results compared:
method
vs. Beckman
ACA
DSA BCO
5.0-
0.853
Albumin
79 Speckn.ns, Slope 0.903
l.le,c.pt.’
0 0.21 #{149}
X -0.30
0 1.1 #{149}
S -20
5.0-
0
I
0
(g/lOOml)
Fig. 11. Total protein results compared:
12/60
6.0-
I
10.0
4.0-
-
0
60
Q
3.0-
3.0-
4
4
0.
1.0-
0-
I
0
I
I
1.0
Technicon
Fig.
HABA
12. Albumin
method
I
I
2.0
I
I
I
3.0
SMA 12/60
results compared:
I
I
4.0
I I T
6.0
0-
6.0
I
(g/IOOml)
ACA
vs.
SMA
CHEMISTRY, Vol. 18, No. 4, 1972
I
I
1.0
I
I
I
2.0
Fig. 14. Albumin
phoresis
S .0-
6
I
3.0
Elecirophoresis
12/60
not be resolved by a calibration
adjustment,
because both slope and intercepts
are involved.
Therefore,
to determine
the validity
of the ACA
method,
we compared
the ACA and a BCG method
as performed
on the Beckman
DSA
(Figure
13).
The paired data analysis gave a t value of 0.787
(Table 4), which indicates that comparable
results
are obtained
by the two BCO methods.
The ACA
values were then compared
with the values determined by electrophoresis
on cellulose acetate;
the
electrophoretic
values compared
favorably
with
those obtained
with the ACA (Figure 14). Paireddata analysis showed a bias of 0.035, a standard
deviation
between
methods
of 0.204 g/100 ml,
and a I value of 1.496. Thus, the ACA method provided valid answers for albumin and the SMA 12/60
results appeared to be in error.
A BCG method was then set up on the SMA 12/60
and the results were compared
to those obtained
with the BCG method
on the ACA (Figure
15).
Paired data analysis gave a I value of 1.746, which
shows that they compare well.
Bilirubin.
Comparison
studies
showed
discrepancies
between results obtained
with the ACA
346 CLINICAL
I
0
I
4.0
6.0
(g/IOOml)
results compared:
ACA
vs. electro.
ALBUMIN
53
-
0
Speclma,s
Slop.
Inl.,c.pt,
9
Y 0.21
0927
0 -029
a’
3.0-
4
S
2.0-
V
0
-
4,
E
.o
0
0
00
I
0
8CG
Fig. 15. Albumin
method
I
I
1.0
I
2.0
I
I
I
3.0
I
4.0
method on SMA 12/60
results compared:
0.0
(g/lOOmI)
ACA
vs.
SMA
12/60
BCG
and the SMA 12/60. As Figure 16 illustrates,
the
median of the distribution
of normal values by the
ACA method
was at least 0.5 mg/100 ml higher than
that by the diazo method. We attempted
to correct
for the blank error by readjusting
the zero setting
DuPont
Bilirubin
ACA
11 spiGImiSs.
lolerc.pts’
78 Normals
Slope L009
0 2.12!
.2J22,
6.0-
S
4.0-
I
3.0-
Technlcon
SMA 12/60
2.0-
89 Normals
1.0-.
0.0-
1.0
Bilirubin
2.0
0’.0
(mg/lOOmI)
Fig. 16. Bilirubin results compared: Histograms of data
from hospital employees for ACA and SMA 12/60 methods
on the ACA (Table 3). The comparison
data then
showed a large amount of scatter (Figure 17). Statistical analysis of the paired data gave a highly significant I value of 4.100.
Discussion
In comparing
results
with patients’
sera, we
hoped that the two instruments
would provide
identical
values, so that the results could be used
interchangeably
in patient treatment.
The glucose
comparison
studies
showed discrepancies
attributable to differences
in specificity
of the methods
being used. Good comparison
data was obtained
with a single channel o-toluidine system, and use of
this method
on the SMA 12/60 would lead to improved performance.
Details for adapting
the otoluidine
procedure
to the SMA 12/60 have been
published
recently
(6); thus, a solution
to this
problem
appears to be at hand and we currently
are evaluating
this method on our SMA 12/60.
Comparability
of results with the enzyme methods has been achieved
for practical
purposes
by
recalibrating
the SMA 12/60 methods.
In practice,
we have done this by adjusting
the set point on
the SMA 12/60 standard
to whatever
value will
give us the same results as the ACA for patients’
sera. We recognize that this is an arbitrary
calibration procedure
and that the use of such a procedure
requires careful documentation
of normal limits by
our laboratory
methods.
However,
this procedure
does permit
us to perform
emergency,
single-request, and profile analyses of alkaline phosphatase,
SOOT, and LDH, and yet provide
comparable
analytical results under all of these conditions.
This calibration
procedure
is also in agreement
with our
general concept of quality control on the SMA 12/60. We consider the methods
used with the SMA
12/60 to be secondary
methods,
which should be
referenced
to other methods
in the laboratory
to
10
Technlcon
Fig. 17.
20
3!0
SMA 12/60
Bilirubin results compared:
40
90
(mq/IOOml)
ACA
vs.
SMA
12/60,
after blank adjustment on ACA
determine
calibration
set points and ultimately
to
control the values that are produced
by the SMA
12/60. Comparison
studies between
methods
are
therefore
part of routine quality
control for our
SMA 12/60.
We consider this to be a practical
approach to problems in our laboratory,
at least until
the time when definitive
and easily performed
enzyme standardization
is practicable
in a routine
service laboratory.
With respect
to comparability
of results,
we
consider the BCG method for albumin
on the SMA
12/60 to be an improvement
over the HABA procedure, because it provides
values that compare
well with those from both the ACA and electrophoresis,
thus again providing
a more consistent
and more easily interpreted
set of laboratory
data.
For bilirubin,
we have not been able to resolve
the differences
between
instruments,
though
the
differences
have been minimized
by adjustment
of the blank on the ACA. Because of this difficulty,
we currently
use the ACA bilirubin
method
only
for emergency
analysis and report results that are
less than 1.5 mg/100 ml only as “below 1.5.”
In summary,
we wanted to know how validly
we could use the ACA and SMA 12/60 together in
routine
laboratory
service. By changing
the albumin method
and adjusting
the calibration
for
albumin
and the enzymes on the SMA 12/60, the
values obtained
can be used interchangeably
in
patient care and treatment,
with restrictions
only
on glucose in uremic patients
and bilirubin
at low
concentrations.
In our laboratory,
the around-theclock emergency
service has been improved
by the
addition of the ACA. This is attributable
both to the
availability
of more emergency
procedures
and to
the increased capacity for night and weekend work,
and emergency
work during
the day. Routine
laboratory
service has been improved
by the adjustments
and modifications
of our SMA 12/60,
as well as by the availability
of the ACA for perCLINICAL
CHEMISTRY, Vol. 18, No. 4, 1972 347
formance
evaluation
based on comparison
studies.
The laboratory
personnel
easily learned to use the
ACA and quickly
came to depend on the ACA to
meet the laboratory’s
service responsibilities.
in the Clinical Laboratory, G. M. Brittin and M. Werner, Edo.
Charles C Thomas, Springfield,
III., 1971, pp 89-98.
2. Perry, B. W., Hosty, T. A., Coker, J. G., Doumas,
B., and
Straumfjord,
J. V., A Field Evaluation of the DuPont Automatic
Clinical Analyzer,
E. I. du Pont de Nemours
and Co., Inc.,
Wilmington,
The computer
plotting
programs
were made available
by
Michael
K. Mansfield (Laboratory
Computer
Facility)
and the
statistical analysis programs by George Cembrowski
and Dr. E.
Clifford Toren (BioAnalytical
Division, Clinical Laboratories).
We also thank Dr. Merle Evenson
and Miss Marian Hunt for
their assistance in preparation
of the manuscript.
References
1. Evenson, M. A., Preliminary
field evaluation
of the DuPont
automatic
clinical analyzer. In Automation
and Data Proce,8aing
348
CLINICAL
CHEMISTRY, Vol. 18, No. 4, 1972
Del.,
1970.
3. Sudduth, M. C., Widish, J. R., and Moore, J. L., Automation
of glucose measurement
using o-toluidine reagent. Amer. J. Clin.
Pat hol. 53, 181 (1970).
4. Barnett,
R. N., and Youden, W. J., A revised scheme for the
comparison of quantitative
methods. Amer. J. Clin. Pathol. 54,
454 (1970).
5. Laessig, R. H., and Schwartz, T. H., Determination
of performance characteristics
of multi-channel
analyzers by a statewide co-operative program. CLIN. CHEM. 17, 646 (1971).
6. Webster, W. W., Stinson, S. F., and Wong, W. H., Manual
procedure
for direct microassay
of serum glucose by use of
o-toluidine,
and its adaptation
to the SMA 12/60 AutoAnalyzer.
CLIN.
CHEM.
17, 1050
(1971).