T H E AMERICAN JOURNAL OF CLINICAL PATHOLOGY
Vol. 44, No. 3
Copyright © 1905 by The Williams & Wilkins Co.
Printed in
U.S.A.
CLINICAL CHEMISTRY QUALITY CONTROL VALUES IN
THIRTY-THREE UNIVERSITY MEDICAL SCHOOL
HOSPITALS
PRELIMINARY REPORT
JON V. STRAUMFJORD, Jit., M.D., P H . D . , AND BRADLEY E. COPELAND, M.D.
Department of Clinical Pathology, University of Alabama School of Medicine, Birmingham, Alabama,
and Departments of Pathology, New England Deaconess Hospital and, Harvard Medical School,
Boston, Massachusetts
Quality control procedures are now
accepted as an important part of all clinical
pathology measurements. 2 • 3 • s Many laboratory directors have requested a set of
quality control values as a guide for judging
performance in clinical chemistry. The
quality control results of individual laboratories have been reported, 1 ' 6 - 7 > 10 but
no composite summary of the quality control
values has been reported from a series of
laboratories large enough to show a dispersion of values from a variety of methods
and instruments.
I t is the purpose of this report to present a
preliminary summary of quality control
values actually obtained in daily practice
by 33 clinical chemistry laboratories in
university medical school hospitals. These
laboratories represent a valid reference
point, as those laboratories affiliated with
medical school hospitals perform comparably.
The data presented is preliminary because it was not possible to clarify completely problems of terminology, units,
methodology, and instrumentation. These
data from a population of reference level
laboratories do present the clinical chemistry
quality control values characteristic of the
day-to-day frame of reference. It is the dayto-day frame of reference which is particularly important in the practice of medicine
as contrasted with the within-day frame of
reference frequently used in research laboratory reports. Individual laboratory directors may use these data for decision making
with greater assurance than has been possible
previously with reported results of single
laboratories.
COLLECTION O F DATA
The quality control questionnaire was
sent to the laboratory directors of 156
hospitals related to the 90 medical schools in
the United States and Canada. Of the 56
replies received, 33 were specific in reporting the day-to-day, 1 standard deviation
quality control values. Twenty-three replies
were not used because of difficulty in
interpretation of the units or expression of
precision used.
RESULTS
The average and range of the 1 standard
deviation quality control values are listed in
Table 1. I t is important to note that these
values include day-to-day variability,
which represents the proper frame of
reference in the practice of laboratory medicine where measurements on patients are
made from 1 day to the next.
The day-to-day quality control values
have been expressed also as coefficient of
variation (Table 1) and the frequency
distribution of each method is shown in
Figure 1. Laboratories appearing at the
extremes of each distribution are significantly different from the averages presented. 6, u
A majority of the laboratories reported
values within certain characteristic limits
labeled "most common range" in Table 2.*
This designation is an approximation, as the
distribution of values is small and tends to
be skewed. These data have been retabulated
with respect to instrument or method, or
both (Table 3).
* Dotted lines in Figures 1, 2, and 3 enclose the
"most common range values."
Received, April 1, 1905.
252
TABLE 1
D A Y - T O - D A Y QUALITY CONTROL V A L U E S IN U N I V E R S I T Y H O S P I T A L S : 1 STANDARD D E V I A T I O N
AND 1 C O E F F I C I E N T OF VARIATION
Analyzed Component
Mean, 1 Standard Deviation*
Mean, 1 Coefficient
of Variation!
Range of t Standard
Deviation?
Glucose
Urea nitrogen
Carbon dioxide
Chloride
Sodium
Potassium
Phosphorus
Calcium
Uric acid
Total protein
Creatinine
Cholesterol
Bilirubin
Amylase
Transaminase
Alkaline phosphatase
3.2 mg./lOO ml.
1.1 mg./lOO ml.
0.8 m E q . / l i t e r
1.3 m E q . / l i t e r
1.5 m E q . / l i t e r
0.12 m E q . / l i t e r
0.19 mg./lOO ml.
0.21 mg./lOO ml.
0.25 mg./lOO ml.
0.16 Gm./lOO ml.
0.11 Gm./lOO ml.
8.7 mg./lOO ml.
0.22 mg./lOO ml.
11 units
4.2 units
3.1
5.S
4.3
1.0
1.1
2.5
4.9
2.3
4.S
2.6
7.8
5.1
7.6
S.l
11.8
10.0
0.5-7.0 (27)
0.15-2.5 (31)
0.36-2.0 (25)
0.35-2.5 (33)
0.56-3.0 (33)
0.01-0.25 (31)
0.01-0.40 (32)
0.07-0.40 (28)
0.10-0.SO (31)
0.03-0.50 (30)
0.03-0.22 (26)
l.S-23 (30)
0.03-0.6 (25)
1.3-34 (19)
0.7-10 (21)
* ± 1 Standard deviation = 67 per cent of population of day-to-day measurements.
f Coefficient of variation = V = ( S D / M ) X 100.
I Numbers in parentheses = number of reports.
Coefficient of voriotion-University Hospitals
(V=fxlOO)
GLUCOSE
C0 2
>o
5 io
till
o
£5
1 3
5
V
7
9
I
11,1
3
5
M
Mf
7 9 II
V
CALCIUM
UREA NITROGEN
>-l5 -|
iioh
£ 5
111a ^
1 3
5
V
7
9
TOTAL PROTEIN
IO
a. 5 -
LM5
V
3
5
ut
7
9
V
15
1 3
I
7
9
PHOSPHORUS
II
4^4-
13 15 17
Coefficient of variation-University Hospitals
(V = 4-XI00)
POTASSIUM
URIC ACID
>.'5
o
§10 h;
K5
10
I
I-
I
5
7
3
9
CHOLESTEROL
II
13
BILIRUBIN
I<r5
HliU
5 7 9
above 2 0 - 4
10
All U f
i
3
5
7
5
9
i t
II
-
1
1
1
1
i
I
inl.ii H . •
3
5
7
9
II
13 15
TRANSAMINASE-SG0T
CREATININE
o
above 2 0 - 5
5io
50-
10
o
a: 5
5
iHllll HI I
7
9
II
,fi, |f I I I , fff | j .
13
3
5
7
9
II
13 15
V
FIG. 2
TABLE 2
D A Y - T O - D A Y Q U A L I T Y C O N T R O L IN U N I V E R S I T Y H O S P I T A L S : M O S T COMMON R A N G E
Analyzed Component
Most Common Range of 1 Standard
Deviation
Number Within or Less
than Most Common
Range
Number of Laboratories Reporting
Glucose
Urea nitrogen
Carbon dioxide
Chloride
Sodium
Potassium
Phosphorus
Calcium
Uric acid
T o t a l protein
Creatinine
Cholesterol
1.0-5.0 mg./lOO ml.
0.6-1.9 mg./lOO ml.
0.6-1.3 mM/liter
0.7-1.7 mEq./liter
1.0-2.0 mEq./liter
0.1-0.2 m E q . / l i t e r
0.08-0.25 mg./lOO ml.
0.10-0.20 mg./lOO ml.
0.10-0.30 mg./lOO ml.
0.10-0.20 Gm./lOO ml.
0.07-O.15 mg./lOO ml.
5.0-10.0 mg./lOO ml.
0.1-0.3 mg./lOO ml.
5-15 units
1-5 Frankel units
24
28
23
26
32
29
25
19
26
26
22
26
20
15
15
27
31
25
33
33
31
32
28
31
30
26
30
25
19
21
Bilirubin
Amylase
Transaminase
254
Sept. 1965
255
CLINICAL CHEMISTRY QUALITY CONTROL VALUES
Coefficient of variation-University Hospitals
(V=-=-xioo)
fcio
SODIUM
10 r
CHLORIDE
I
I
z
5 -
LU
=3 5
IIIIIUJUJL
1.0
III
J4lL
1.5 2.0 2.5
^n
1.0
1.5
2.0
12.5
V
AMYLASE
ALK. PHOS.
10
olO r
3
*>
5 -
JLML
10
li^il^
M-+
15 20
10
15
•4
20
V
V
FIG.
DISCUSSION
Laboratories whose day-to-day quality
control standard deviation is within the
limits of the "most common range" (Table
2)1 are performing work comparable to
more than 90 per cent of the reporting
laboratories. The comparison of methods
and instruments (Table 3) does not show
any striking differences.4
These data are presented to give a preliminary set of reference points for the
evaluation of performance in the clinical
chemistry laboratory. In the process of
evaluation of laboratory performance there
are 3 pitfalls. The first is the attempt to be
too precise, which often leads to unconscious
or conscious bias, as well as unnecessary
expense. The second is the acceptance of
excessive variability which may negate the
medical usefulness of the measurements. A
third difficulty is the definition of the frame
of reference, the conditions for the collection
of data, and the method of expressing the
estimate of precision.
3
The data presented represent the day-today frame of reference which has been
adopted extensively in the United States
and Canada through the institution of daily
quality control programs in hospital laboratories. This frame of reference is (1)
single daily measurements, and (2) measurements made at the same time as regular unknown specimens.
As it is economically wasteful to achieve
precision not utilized in the medical decisionmaking process, the horizon should not be
limited to the achievement of the smallest
absolute numerical value. The medical
purpose of the measurement should be given
primary consideration in order to determine
optimal quality control goals. The goals for
small hospitals should be the same as those
for large hospitals. 9
CRITERIA FOR FUTURE COMPILATIONS OF 1
STANDARD DEVIATION QUALITY
CONTROL VALUES
The problems encountered during the
256
Vol. U
STKAUMFJORD AN]) COPELAND
process of collating data from the cooperative
laboratories have re-emphasized the problems of terminology and communication
between laboratories where a multiplicity of
methods, instruments, and units of expression of precision are employed. An improved
questionnaire is being prepared. In cooperation with the Council on Clinical
TABLE 3
D A Y - T O - D A Y Q U A L I T Y CONTROL—STANDARD D E V I A T I O N ( 1 ) — U N I V E R S I T Y H O S P I T A L S
R E L A T E D TO M E T H O D OR I N S T R U M E N T AND P O O L CONCENTRATION R A N G E
Analyzed Component
Glucose
Technic or Instrument or Both
Number of
Reports
Average, 1 Standard
Deviation
AutoAnalyzer
Glucose oxidase
22
1
3.0 mg./lOO ml.
3.0 mg./lOO ml.
Somogyi-Nelson
1
4.0 mg./lOO ml.
Range of (Pool
Concentration
69-134
(one 215 S.D. (1)
of 7.6)
Urea nitrogen
AutoAnalyzer
AutoAnalyzer (Marsh)
22
4
1.07 mg./lOO ml.
1.05 mg./lOO ml.
12-37
11-41
Carbon dioxide
AutoAnalyzer
Titration
Microgasometer
Volumetric (Van Slyke)
13
4
2
2
0.80 mM/liter
0.83 mM/liter
0.50 & 0.85 mM/liter
1.2 & 2.0 mM/liter
14-27.5
Chloride
AutoAnalyzer
Chloridometer
Shales and Shales
AutoAnalyzer
Coleman
Baird
11
12
6
13
7
7
1.4 mEq./liter
1.0 mEq./liter
1.3 mEq./liter
1.49 mEq./liter
1.24 mEq./liter
1.64 mEq./liter
94-104
95-107
95-102
119-143
130-149
135-151
Potassium
AutoAnalyzer
Coleman
Baird
12
7
7
0.13 mEq./liter
0.11 mEq./liter
0.10 mEq./liter
3.9-7.2
3.8-5.7
4.3-4.9
Phosphorus
Fiske-Subbarow-Klett
Fiske-SubbarowColeman
Fiske-Subbarow-Evelyn
Fiske-Subbarow-AA
Fiske-Subbarow
4
4
0.15 mg./lOO ml.
0.28 mg./lOO ml.
3.5-6.8
3.8-5.5
2
8
5
0.14 mg./lOO ml.
0.15 mg./lOO ml.
0.20 mg./lOO ml.
4.0-4.2
2.1-4.6
3.3-4.4
Calcium
ClarkCollip
Coleman
AutoAnalyzer
5
7
6
0.33 mg./lOO ml.
0.22 mg./lOO ml.
0.18 mg./lOO ml.
7.8-18.0
9.0-12.0
8.9-10.0
Uric acid
AutoAnalyzer
Carraway
Brown
Henry
Folin
6
4
4
4
3
0.30
0.18
0.30
0.16
0.23
mg./lOO ml.
mg./lOO ml.
mg./lOO ml.
mg./lOO ml.
mg./lOO ml.
3.9-6.7
4.6-5.1
4.1-6.0
4.4-6.2
2.8-4.3
Total protein
Biuret-Auto Analyzer
Biuret-Coleman
Biuret-KIett
0.14 Gm./lOO ml.
0.15 Gm./lOO ml.
0.12 Gm./lOO ml.
4.6--7.1
6.5-7.0
6.3-7.9
Sodium
10
7
6
Sept. 1965
CLINICAL CHEMISTRY QUALITY CONTROL VALUES
257
T A B L E 3 {Cont.)
Analyzed Component
Creatinine
Technic or Instrument or Both
Number of
Reports '
Average, 1 Standard
Deviation
Range of Pool
Concentration
Alkaline picrate (Jafle)
Alkaline picrate (Klett)
Alkaline picrate
(Coleman)
Alkaline picrate
(Evelyn)
Alkaline picrate (AA)
(2)
3
4
0.10 mg./lOO ml.
0.09 mg./lOO ml.
0.09 mg./lOO ml.
0.9-1.6
1.1-1.5
1.9-2.2
3
0.08 mg./lOO ml.
1.4-2.0
5
0.11 mg./lOO ml.
1.0-2.5
0.18 mg./lOO ml.
0.10 mg./lOO ml.
0.36 mg./lOO ml.
Cholesterol
Too varied to tabulate
(see Table 1)
Bilirubin
Evelyn-Malloy
Evelyn-Malloy (Klett)
Evelyn-Malloy
(Coleman)
10
3
3
Amylase
Somogyi saccharogenic
Amyloclastic
(Carraway)
7
5
Transaminase
Reitman-Frankel
17
4.4
16-93
Alkaline
phosphatase
King-Armstrong
6
1.1
7.7-15
PBI
Barker
Chloric acid
4
3
0.34
0.50
6.3-19.3
2.3-9.8
Chemistry of the American Society of
Clinical Pathologists, a set of specifications
is being evolved for defining an acceptable
day-to-day quality control 1 standard
deviation value. This will insure that the
data will be uniform and that comparisons
will be made in the same frame of reference.
Criteria
1. Each determination must represent a
different day.
2. The reported day-to-day quality control 1 standard deviation should represent a
population of at least 20 determinations, and
this number should be stated.
3. The type of quality control pool
material is stated.
4. A description of how the material was
pooled and how it was handled prior to the
determinations is given.
5. The mean concentration level of the
quality control pool is reported.
7.3 units
11.0 units
0.5-4.3 (one20)
0.52-5.4
0.40-19.8
65-300
102-211
6. If the reported value represents the
average of 12 monthly estimates, this is to be
stated.
7. Each determination is to be a single
measurement and not the average of more
than one, or it shall be clearly indicated that
the reported measurement is an average of
" n " observations.
8. The data must represent consecutive
determinations.
9. None of the consecutive determinations
may be discarded.
SUMMARY AND CONCLUSIONS
1. A summary of day-to-day climcal
chemistry quality control values is presented, representing data from 33 medical
school-related hospital laboratories.
2. The day-to-day quality control values
may be used as a preliminary guide in
judging the performance of clinical chemistry
quality control programs.
258
STRATJMFJORD AND COPELAND
3. No differences were identified between
instruments or methods.
4. Further efforts are in progress to communicate with a larger number of cooperating laboratories, using a more specific
questionnaire.
5.
6.
7.
REFERENCES
1. Benenson, A. S., Thompson, H. L., and
Klugerman, M. R.: Application of laboratory controls in clinical chemistry. Am. J.
Clin. Path., 25: 575-584, 1955.
2. Benson, E. S.: How good is this laboratory
value? Postgrad. Med., 26: A-27-A-28,
1959.
3. Carroll, G. J., and Jenkins, 0 . : Quality control in your hospital. Virginia M. Month.,
91: 211-214, 1964.
4. Copeland, B. E.: Standard deviation, a practical means for the measurement and control of the precision of clinical laboratory
8.
9.
10.
11.
Vol. U
determinations. Am. J. Clin. Path., 27:
551-558, 1957.
Davidsohn, I., and Wells, B. B.: Clinical
Diagnosis of Laboratory Methods. Philadelphia: W. B. Saunders Co., 1964, p. 20.
Freier, E. F., and Rausch, V. L.: Quality control in clinical chemistry. Am. J. M. Tech.,
24: 195-207, 1958.
Levey, S., and Jennings, E. R.: The use of control charts in the clinical laboratory. Am.
J. Clin. Path., 20: 1059-1066, 1950.
Quality Control Manual. Chicago: Commission on Continuing Education, American
Society of Clinical Pathologists.
Seminar on Quality Control Performance
Goals. Council on Clinical Chemistry, Annual Meeting, American Society of Clinical
Pathologists, Chicago, October 1963.
Sparapani, A., and Berry, R. E.: Pools of
frozen serum in the quality control in clinical chemistry. Am. J. Clin. Path., 1$:
129-132, 1964.
Youden, W. J.: Statistical Methods for Chemists. New York: John Wiley & Sons, 1951,
p. 29.