CLINICAL CHEMISTRY
Original Article
Accuracy of Portable Blood
Glucose Monitoring
Effect of Glucose Level and Prandial State
DINO A. VALLERA, M.D., MICHAEL G. BISSELL, M.D.,
AND WILLIAM BARRON, M.D.
PH.D.,
M.P.H.,
Glucose was determined on capillary and venous blood samples
from 274 adult diabetics by three different methodologies: the
Glucoscan 2000® and Accu-Check II® portable glucose meters
(capillary) and the Kodak Ektachem 700® analyzer (venous).
Both glucose meters correlated significantly with the Ektachem
results. A significant positive bias was found for the Glucoscan
compared with Ektachem, not found with the Accu-Check II.
The Accu-Check performed better than the Glucoscan at venous
plasma glucose levels < 1 g/L. The mean error of Glucoscan
determinations was significantly greater and biased positive when
the measurement was performed within 4 hours of eating,
whereas no such effect was seen with Accu-Check error. Multiple
regression analysis revealed that the Glucoscan measurement
was independently influenced by both venous plasma glucose
and prandial state, whereas the Accu-Check II measurement
was not dependent on either variable. The within-run precision
for both glucose meters were comparable. (Key Words: Portable
glucose monitoring; Accuracy.) Am J Clin Pathol 1991;95:247252
Portable capillary blood glucose meters have been used
extensively in both inpatient and outpatient settings for
many reasons, including patient and physician convenience and cost.1,2 Although the accuracy and precision
of this technology have been addressed by a number of
previous investigators,3,4 many of these studies have had
considerable limitations. For example, sample sizes are
often small,5"7 meter accuracy frequently is addressed only
through determination of the correlation coefficient between meter and reference laboratory methods,5,8"12 and
the impact of ambient plasma glucose levels on accuracy
often is neglected. Furthermore, we are aware of only one
study that has addressed the impact of prior feeding on
the concordance between capillary blood glucose measured by a portable meter and venous plasma glucose de-
termined by a laboratory reference methodology.12 Consideration of this factor is important because there may
be significant peripheral tissue glucose extraction in the
postprandial state,13 resulting in venous plasma levels that
are considerably lower than capillary values.
The present investigation was designed to address a
number of these issues by performing a large number of
capillary blood glucose determinations on two currently
popular instruments, analyzing differences between portable meter and standard laboratory measurements as a
function of both ambient plasma glucose level and the
time since the patient's last meal.
METHODS
Study subjects included 274 adult diabetics on whom
a blood glucose level had been requested by their primary
From the Departments of Pathology, Medicine, and Obstetrics
and
care
physician in the University of Chicago Health Service,
Gynecology, University of Chicago Hospitals, Chicago, Illinois. a large internal medicine clinic with more than 50,000
Received September 18, 1989; accepted for publication July 24, 1990. outpatient visits per year. Participants included patients
on dietary therapy only, on oral hypoglycemic agents and
Dr. Vallera is currently with the Department of Pathology, Hinsdale
Hospital, Hinsdale, Illinois; Dr. Bissell is currently with the Department on insulin. Each subject was asked when he had last eaten,
of Clinical Pathology, City of Hope National Medical Center, Duarte,
and the time was recorded to the nearest 30 minutes.
California.
Supported by Boehringer Mannheim Diagnostics, Indianapolis, InBlood was obtained from an antecubital vein and placed
diana.
immediately into a tube containing potassium oxalate
Address reprint requests to Dr. Bissell: Department of Clinical Pathology, City of Hope National Medical Center, 1500 East Duarte Road, (14.0 mg) and sodium fluoride (17.5 mg) (Becton Dickinson Vacutainer Systems, Rutherford, NJ). Plasma obDuarte, California 91010-0269.
247
248
CLINICAL CHEMISTRY
Original Article
tained from the specimen was analyzed for glucose in the
General Clinical Chemistry Laboratory of the University
of Chicago Hospitals on the Ektachem 700® analyzer
(Eastman Kodak Co., Rochester, NY), which uses a glucose oxidase-based reflection densitometric method.
Within 4 minutes after venipuncture, the patient's finger
was punctured with a spring-loaded lancet to obtain a
drop of capillary whole blood. This was analyzed for glucose with either the Glucoscan 2000® with Glucoscan test
strips (Lifescan, Inc., Mountain View, CA) or the AccuCheck II® with Chemstrip bG test strips (Boehringer
Mannheim Diagnostics, Indianapolis, IN). All determinations were performed by a single nurse who was trained
in the operation and quality control of both instruments
as directed by the manufacturers. One instrument of each
type was used for the entire study.
The precision of the Ektachem 700 was assessed by
performing 20 repeated glucose determinations on a single
sample over 20 consecutive minutes and by analyzing the
same sample once daily on 20 consecutive days. Precision
of each portable meter was evaluated by daily determinations of the glucose concentration of a standard test
solution (provided by the manufacturer) for 20 days. In
addition, the precision of the entire portable glucose meter
methodology was assessed for each instrument by performing 20 repeated capillary blood glucose determinations on a single subject over a 30-60 minute period.
The statistical approach used to assess the agreement
between each meter and the laboratory reference method
is a modification of that suggested by Bland and Altman.14
First, least squares linear regression analysis was used to
assess correlations between meter and Ektachem determinations. Next, two-tailed paired /-tests were performed
to evaluate the difference between meter and Ektachem
determinations (referred to here as "meter bias" or "error") and to compare the magnitude of these two differences for the two meters. In addition, 95% confidence
intervals (CI) were calculated for the mean bias for each
meter.
To determine whether meter bias was dependent on
plasma glucose level, we performed a linear regression of
the difference between meter and Ektachem measurements on the Ektachem value. To further clarify this relationship, data were stratified in 1 g/L increments according to the Ektachem value, and an analysis of variance
was performed, followed by two-tailed two sample Mests
to assess differences between the meters at various levels
of venous plasma glucose.
To analyze the impact of prior meal ingestion on monitor accuracy, meter and Ektachem values were grouped
by the length of time that had passed since the last meal.
Preliminary analysis separating data into four groups (02.0 hours, 2.5-4.0 hours, 4.5-6.0 hours, and >6.0 hours)
indicated that results for groups 1 and 2 were similar, as
were those for groups 3 and 4; therefore, data were combined into two groups, 0-4.0 hours and >4.0 hours since
the last meal, and two-tailed, paired and two-sample ttests were performed to assess group differences. Finally,
a multiple regression analysis was performed to assess the
independent contributions of (1) the Ektachem value, and
(2) the time since the last meal, on meter error. Data are
reported as mean ± 1 SD. A P value of <0.05 was considered significant, except where multiple testing was performed, in which case the critical P value was adjusted
by the Bonferroni method (both uncorrected and Bonferroni P values are presented). All calculations were performed on a microcomputer using SYSTAT software.
Precision evaluation experiments were performed on
both the Accu-Check II and the Ektachem according to
the National Committee for Clinical Laboratory Standards (NCCLS) Guidelines EP5T. Briefly, manufacturers'
supplied glucose control material was analyzed in duplicate, in two runs per day, for 20 days. Two analyte concentrations were tested for each method. This data was
analyzed to provide an estimate of within-run and total
imprecision. For the Accu-Check II, the determinations
were performed by the same trained nurse who performed
the patient determinations. The Ektachem study was performed by trained medical technologists in the General
Clinical Chemistry Laboratory.
The Glucoscan 2000 could not be included in this phase
of the study because of the nature of its control materials.
These were packaged in small plastic vials and, according
to the manufacturer's instructions, are to be used within
24 hours of opening. This would necessitate the use of 20
different vials of control material for each analyte concentration to complete the study and would introduce
another source of variability into the data.
RESULTS
A total of 277 determinations were made with the Glucoscan 2000, and 232 were performed on the Accu-Check
II. There was a highly significant correlation between capillary (meter) and venous (Ektachem) glucose values for
both instruments:
Glucoscan: meter value = 0.84 X (Ektachem value)
+ 37.1, r = 0.94
Accu-Check: meter value = 0.92 X (Ektachem value)
+ 14.9, r = 0.94
Despite these results, further evaluation disclosed significant differences in performance of the two meters.
Capillary glucose values measured with the Glucoscan
averaged 1.91 ± 0.84 g/L (range = 0.29-4.50 g/L; n
= 277), whereas venous plasma glucose values on the same
A.J.C.P. • February 1991
VALLERA, BISSELL, AND BARRON
Accuracy of Portable Blood Glucose Monitoring
subjects measured with the Ektachem averaged 1.85
± 0.96 g/L (range = 0.24-5.16 g/L), a highly significant
difference (P = 0.001). The average absolute difference
between the Glucoscan and Ektachem was 0.065 ± 0.326
g/L (95% confidence interval = 0.026-0.104), and the
average percentage difference was 8.8 ±21.6% (95% confidence interval = 6.2-11.3). The observation that neither
of these 95% confidence intervals includes 0 supports the
given result (i.e., the mean Glucoscan 2000 and Ektachem
values are significantly different from one another).
Mean capillary glucose values determined with the
Accu-Check II were 1.95 ± 0.99 g/L (range = 0.22-5.00
g/L; n = 232), and paired venous samples measured on
the Ektachem averaged 1.94 ± 1.01 g/L (range = 0.246.05 g/L), a difference that was not significant (P = 0.93).
The mean difference between the Accu-Check and Ektachem was 0.002 ± 0.35 g/L (95% confidence interval
= -0.017-+0.39), data which confirm the lack of difference between Accu-Check and Ektachem determinations.
For the Glucoscan, 79.8% of determinations were
within 20% of the correct value, whereas 87.9% of the
Accu-Check measurements were in this range. Fourteen
Glucoscan (5.0%) and five Accu-Check (2.2%) values deviated more than 50% from that determined on the Ektachem. Direct comparison of the average bias of the two
meters indicated a highly significant difference when
measured as a percentage of the Ektachem value. (Glucoscan: 8.8 ± 21.6%; Accu-Check: 1.1 ± 21.8%, P
< 0.001), and a trend in the same direction when the bias
was expressed in g/L (Glucoscan: 0.065 ± 0.326 g/L; AccuCheck: 0.002 ± 0.351 g/L, P = 0.038, Bonferroni critical
value: P = 0.025).
Next, we analyzed the effect of the venous plasma glucose level (Ektachem measurement) on the accuracy of
each meter. For the Glucoscan there was a significant linear correlation between the meter error expressed in either
absolute [(Glucoscan value) - (Ektachem value) = -0.17
X (Ektachem value) + 37.1, r = 0.486, P < 0.001] or
percentage terms [% difference between Glucoscan and
249
Ektachem = -0.11 X (Ektachem) + 28.6, r = 0.477, P
< 0.001]. This effect was much less evident for the AccuCheck II, and was significant only for the error measured
in absolute terms [difference (g/L) = -0.08 X (Ektachem)
+ 15.6, r = 0.229, P< 0.001; % difference = -0.02 X (Ektachem) + 4.8, r = 0.09, P = 0.18].
This effect is better appreciated when the data are
grouped in 1-g/L intervals of the Ektachem value (Table
1). The average bias of the Glucoscan is more than 20%
(95% confidence interval = 19-28) when the Ektachem
value is less than 1 g/L, becomes minimal in the range
2-3 g/L, and is more than - 1 0 % when the venous plasma
level is >4 g/L. In contrast, the error of the Accu-Check
at the lowest glucose values averaged - 6 ± 15% (95%
confidence interval = - 2 — 11; P < 0.005 vs. Glucoscan
error, Bonferroni critical P = 0.01) and varied from —6.3%
to +7.8% in other ranges of venous glucose (= not significant vs. Glucoscan for each of these ranges). Thus, the
Accu-Check performed better (i.e., had less bias) than the
Glucoscan primarily when the venous plasma glucose was
<lg/L.
It also is of interest to note that all meter determinations
with a difference from the Ektachem value of greater than
90% occurred in the most commonly encountered venous
plasma glucose range (1-2 g/L) for both the Glucoscan
(n = 4) and Accu-Check (n = 3). These seven determinations were made on four different subjects; on two of
these, other meter measurements were within 20% of Ektachem values. When these seven outliers were excluded,
the mean measurement error in the 1-2 g/L range was 8
± 13% (95% confidence interval = 6-11) for the Glucoscan
and 3 ± 16% (95% confidence interval = -0.3-+7.0) for
the Accu-Check (P = 0.023, Bonferroni critical P = 0.01).
Assessment of the effect of prior meal ingestion on
measurement bias indicated further differences in meter
performance (Table 2). The mean error of Glucoscan determinations was significantly greater and biased in a positive direction when the measurement was performed
within 4 hours of eating, whereas recent food intake did
TABLE 1. METER BIAS IN ABSOLUTE (mg/dl) AND PERCENTAGE TERMS AS A FUNCTION
OF VENOUS PLASMA GLUCOSE LEVEL
Venous
Plasma
Glucose
(q/L)
<1.0
1.0-1.9
2.0-2.9
3.0-3.9
^4.0
Glucoscan 2000 Bias
3'L
0.18
0.16
-0.05
-0.11
-0.52
±0.13
+ 0.34*
± 0.28
±0.25
± 0.29
Accu-Check II Bias
%
H
23 ± 17
12 ± 2 5 *
-2+11
-3 ±8
-11 ± 6
55
125
63
23
11
• When four outliers {% difference from Ektachem >90%) were excluded, differences were 0.11
± 0.20 g/L and 8 ± 13%.
9IL
-0.05
0.11
0.01
-0.23
-0.12
±0.12
±3.9|
± 0.26
± 0.38
±0.67
%
n
- 6 ± 15
8±30f
1 ± 11
6+10
1 ± 13
44
90
61
28
9
t When three outliers were excluded, differences were 0.05 ± 0.25 g/L and 3 ± 16%.
Results are expressed as mean ± SD; n = number of paired determinations.
Vol. 95 • No. 2
250
CLINICAL CHEMISTRY
Original Article
GLUCOSCAN 2000
TABLE 2. EFFECT OF PRIOR MEAL INGESTION
ON METER BIAS
Time Since Last Meal
Instrument Units
Glucoscan
Accu-Check
g/L
%
g/L
%
0-4 hours
0.102
11.4
0.016
2.1
n
>4 hours
171
± 0.34
0.005 ±
171
±23.6
4.5 ±
± 0.38* 149 -0.024 ±
±23.4§ 149 -0.8 ±
n
0.28*
16.9f
0.28
18.6
106
106
83
83
I
* P < 0.02 for the comparison with the 0-4 hour time period.
t P < 0.001 for the comparison with the 0-4 hour time period.
X P = 0.038 for the comparison with Glucoscan.
§ P < 0.001 for the comparison with Glucoscan.
Bonferroni critical P = 0.0125.
Results are expressed as mean ± SD; n = number of paired determinations.
-60
-50
-40
-30
-20
-10
10
20
30
40
DIFFERENCE (X)
not appear to have a significant effect on the Accu-Check
meter error. Furthermore, the Accu-Check performed
significantly better (i.e., less bias) compared with the Glucoscan only for measurements made less than 4 hours
after the last meal.
Finally, multiple regression analysis was performed to
determine whether the level of venous plasma glucose
and the time since the last meal had independent effects
on meter bias. Regression coefficients (Table 3) demonstrate that the bias of the Glucoscan, in both g/L and
percent, is independently influenced by both plasma glucose and prandial state. In contrast, the bias of the AccuCheck, as a percentage of the Ektachem value, was dependent upon neither of these variables, although the bias
in g/L was significantly influenced, albeit to a smaller degree than for the Glucoscan, by the venous plasma glucose.
For the Accu-Check II meter, the overall mean of all
determinations using the high glucose control material
was 3.093 g/L. The within-run precision was 0.177 g/L,
whereas the between-run precision was 0.268 g/L (coefficient of variation = 8.7%). With the low concentration
glucose control, the overall mean was 0.409 g/L, with the
within-run precision being 0.0185 g/L and the betweenrun precision being 0.0236 g/L (coefficient of variation
= 6.4%).
TABLE 3. COEFFICIENT OF MULTIPLE REGRESSION
ANALYSIS EVALUATING THE DEPENDENCE OF
METER BIAS ON PLASMA VENOUS GLUCOSE
AND TIME SINCE LAST MEAL
Instrument Units
Glucoscan
Accu-Check
g/L
%
g/L
%
Glucose
Level
-0.17
-0.11
-0.08
-0.02
±0.02
±0.01
± 0.02
+ 0.01
Time Interval
<0.001
<0.001
<0.001
0.16
-8.94
-6.47
-4.87
-3.12
±3.50
±2.32
± 4.69
±2.98
0.011
0.006
0.30
0.296
Results are expressed as mean ± SE. "Time period since last meal" is categorized into "0-4
hours" or ">4 hours."
ACCUCHECK II
-60
B
-50
-40
-30
-20
-10
10
20
30
40
50
60
DIFFERENCE (%)
FIG. 1. A (upper). Percent differences between EKTACHEM and
GLUCOSCAN 2000 values grouped according to the level of venous
glucose determined by the EKTACHEM. Note that the ambient level
of venous glucose has a significant effect on meter bias and that when
venous glucose is less than 1 g/L, bias is approximately +20%. B (lower).
Percent differences between EKTACHEM and ACCUCHECK II values
grouped according to the level of venous glucose determined by the Ektachem. There is no significant relationship between meter bias and venous plasma glucose levels.
With the Ektachem, using the high concentration glucose control, the overall mean was 4.28 g/L, with the
within-run precision being 0.0172 g/L, between-run precision being 4.08 g/L (coefficient of variation = 0.95%).
For the low glucose control, the overall mean was 0.827
g/L, with within-run precision being 0.0052 g/L and between-run precision being 0.0121 g/L (coefficient of variation = 5.5%).
In the whole method precision study, both the AccuCheck II and Glucoscan 2000 were tested. Using the Glucoscan 2000, the first volunteer's mean blood glucose
concentration was 0.94 g/L, with SD of 0.0615 g/L (coefficient of variation = 6.5%). The second volunteer was
tested with the Accu-Check II, yielding a mean blood glu-
A.J.C.P. • February 1991
VALLERA, BISSELL, AND BARRON
251
Accuracy of Portable Bh <d Glucose Monitoring
cose concentration of 0.735 g/L, with SD of 0.0405 g/L
and coefficient of variation of 5.5%. Repetitive sampling
(n = 20) of the Ektachem high glucose control resulted
in a mean concentration of 4.398 g/L, with SD of 0.0405
g/L and coefficient of variation of 0.53%. For the low
control, the mean concentration was 0.817 g/L, with SD
of 0.0047 g/L and coefficient of variation of 0.58%.
DISCUSSION
This study critically evaluated the performance of two
popular blood glucose meters in a busy clinical setting
and attempted to identify variables that might account
for any observed bias. As reported by others, 815 we found
that both meters' readings were highly correlated (r = 0.94)
with the laboratory reference method; however, additional
analysis disclosed that, on average, the Accu-Check II
provided more accurate determinations, with a mean bias
of only 1. i % compared with 8.8% for the Glucoscan 2000.
Yet more detailed evaluation disclosed that the greater
bias of the latter instrument occurred primarily at lower
levels of plasma glucose and when the patient had eaten
within several hours of capillary glucose measurement.
There have been numerous published reports that purportedly have investigated the accuracy of portable blood
glucose monitors.5"8,10,11,15"20 However, as discussed in
detail by Bland and Altman,14 many investigators inappropriately report only the correlation coefficient between
measurements made by meter and some reference methodology.5"12 Such a statistic fails to provide clinically relevant information {i.e., how much does the meter determination deviate from the true [laboratory reference]
value, and does this deviation change at various levels of
venous plasma glucose).
Godine and colleagues15 evaluated the accuracy of the
Accu-Check meter when used by staff nurses and found
a mean error of 8 ± 7%, whereas Landon and colleagues,20
studying the same meter, observed a mean deviation of
approximately 15%. Brooks and co-workers'8 found a
mean bias of—0.06 ± 0.30 g/L for the Accu-Check II and
0.08 ± 0.27 g/L for the Glucoscan 2000 (percentage data
not available). Results of average bias for the two meters
in the present study were in the ranges cited, with a mean
error for the Accu-Check II of 1 ± 22% (0 ± 0.35 g/L)
and 9 ± 22% (0.06 ± 0.33 g/L) for the Glucoscan 2000.
Although the mean measurement error (as a % of the
venous glucose level) of both glucose meters was relatively
small (<10%; 95% confidence interval for mean bias:
Glucoscan: 6.2-11.3%; Accu-Check II: -1.7-4-3.9%), this
does not provide an estimate of a given capillary glucose
determination, a parameter of considerable clinical importance. The latter is better estimated by the 95% limits
of agreement (i.e., mean error ± 2 SD), which in the pres-
ent study allow one to be 95% certain that a given glucoscan measurement was between - 3 4 % and +52% of
the laboratory reference value and that an Accu-Check
determination was between —43% and +45% of this value.
When viewed in this light, the two meters do not appear,
on average, to differ as much as suggested by comparison
of the mean bias. Furthermore, the range of these limits
make it clear that portable blood glucose meter results
must be interpreted with caution, particularly in those
ranges where a change in therapy may have substantial
adverse effects.21
Overall estimates of glucose meter bias as described
may be misleading if this bias is significantly dependent
on the level of venous plasma glucose (e.g., the bias may
be large at one glucose level and minimal at another).
Indeed, we found a significant linear relationship between
Glucoscan 2000 meter error and venous plasma glucose,
with highest errors at the lowest levels of plasma glucose,
a phenomenon not observed for the Accu-Check II. Two
previous studies of earlier models of the Accu-Check meter
provided similar results.6,20 When we stratified venous
glucose levels (Table 1), it was discovered that the major
difference between the two meters occurred at concentrations of <1 g/L, at which level the mean bias of the Glucoscan was +23% (95% limits of agreement: +6-+40%),
whereas the average error for the Accu-Check II was —6%
(95% limits of agreement: -21-+9%).
These observations may have important clinical implications. For example, when rigid metabolic control is
being attempted, such as is standard during diabetic
pregnancy10,22 (for which desired fasting and postprandial
glucose levels are <1 and <1.2 g/L, respectively), Glucoscan 2000 results may lead to excessive insulin administration. On the other hand, use of Accu-Check II would
be somewhat more likely to lead to unacceptably high
blood glucose levels. Such conclusions highlight the need
to understand glucose meter performance at levels of
blood glucose that are likely to lead to changes in therapy.
Another factor that might affect meter accuracy is the
proximity of glucose measurement to the patient's last
meal because significant forearm glucose uptake occurs
in the postprandial state.13 This could lead to capillary
(meter) glucose levels that are significantly higher than
venous (Ektachem) if food had been consumed shortly
before measurement. 23 We are aware of only one study
that addressed the impact of this phenomenon on the
apparent bias of portable meter capillary glucose determinations. 12 In the fasting state, capillary determinations
exceeded venous glucose levels by 14%; however, 1 and
2 hours after a 100-g glucose load, capillary measurements
were, respectively, 20% and 19% higher than venous determinations. Surprisingly, we found a similar effect only
with the Glucoscan 2000 and not with the Accu-Check
Vol. 95 • No. 2
252
CLINICAL CHEMISTRY
Original Article
II (Table 2). Furthermore, multiple regression analysis
indicated that this was not simply due to the positive bias
of the Glucoscan 2000 at certain levels of venous glucose.
Thus, we have no explanation for this observation, but
the data indicate that a greater allowance for error must
be taken into account if the Glucoscan 2000 is used to
measure capillary glucose in the postprandial state.
In considering all of these statistics, one must balance
factors such as availability, turnaround time, convenience,
and portability against the difference in accuracy and precision in various testing systems. These factors may become more or less important in different clinical settings.
For example, accuracy and precision may be more important in measurements used to adjust insulin doses in
a "rigidly" controlled diabetic, whereas ease of operation
and availability may have increased importance in less
tightly controlled patients.
9.
10.
11.
12.
13.
14.
15.
16.
REFERENCES
17.
1. American Diabetes Association. Bedside blood glucose monitoring
in hospitals. Diabetes Care 1986;9:89.
2. Belsey R, Morrison JI, Whitlow KJ, Baer DM, Nelson S, Hardwick
DF. Managing bedside glucose testing in the hospital. JAMA
1987;258:1634-1637.
3. Rasaiah B. Self-monitoring of the blood glucose level: potential
sources of inaccuracy. Can Med Assoc J 1985;132:1357-1361.
4. Villeneuve ME, Murphy J, Mazze RS. Evaluating blood glucose
monitors. Am J Nurs 1985;11:1258-1259.
5. Gifford-Jorgensen RA, Borchert J, Hassanein L, Tilzer GA, Eaks
GA, Moore WV. Comparison offiveglucose meters for self-monitoring of blood glucose by diabetic patients. Diabetes Care 1986;9:
70-76.
6. James K, Latham D, Marrero J, Barrett DA. Capillary blood glucose
measured by the laboratory phlebotomy team. Laboratory Medicine 1985;16:417-421.
7. Webb DJ, Lovesay JM, Ellis A, Knight AH. Blood glucose monitors:
a laboratory and patient assessment. Br Med J 1980;1:362-364.
8. Chiasson JL, Morrisset R, Hamet P. Precision and costs of techniques
18.
19.
20.
21.
for self-monitoring of serum glucose levels. Can Med Assoc J
1984;130:38-43.
Drucker RF, Williams DRR, Price CP. Quality assessment of blood
glucose monitors in use outside the hospital laboratory. J Clin
Pathol 1983;36:948-953.
Marquette GP, Dillard T, Bietla S, Niebyl JR. The accuracy of visual
and meter determinations of blood glucose with the use of Chemstrip bG. Am J Obstet Gynecol 1985;153:883-884.
Shapiro B, Savage PJ, Lomatch D, et al. A comparison of accuracy
and estimated cost of methods for home blood glucose monitoring.
Diabetes Care 1981;4:396-403.
Weiner CP, Faustich M, Burns J, Fraser L, Whitaker L, KJugman
M. The relationship between capillary and venous glucose concentration during pregnancy. Am J Obstet Gynecol 1986; 155:
61-64.
Jackson RA, Peters N, Advani U, et al. Forearm glucose uptake
during the oral glucose tolerance test in normal subjects. Diabetes
1973;22:442-458.
Bland JM, Altman DG. Statistical methods for assessing agreement
between two methods of clinical measurement. Lancet 1986; 1:
307-310.
Godine JE, Hurxthal K, Nathan DM. Bedside capillary glucose
measurement by staff nurses in a general hospital. Am J Med
1986;80:803-806.
Aziz S, Hsiang YH. Comparative study of home blood glucose monitoring devices: Visidex, Chemstrip bG, Glucometer, and AccuCheck bG. Diabetes Care 1983;6:529-532.
Barr B, Leichter SB, Taylor L. Bedside capillary glucose monitoring
in the general hospital. Diabetes Care 1984;7:261-264.
Brooks KE, Rawal N, Henderson AR. Laboratory assessment of
three new monitors of blood glucose: Accu-Check II, Glucometer
II, and Glucoscan 2000. Clin Chem 1986;32:2195-2200.
Clements RS, Keane NA, Kirk KA, Boshell BR. Comparison of
various methods for rapid glucose estimation. Diabetes Care
1981;4:392-395.
Landon MB, Cembrowski GS, Gabbe SG. Capillary blood glucose
screening for gestational diabetes: a preliminary investigation. Am
J Obstet Gynecol 1986;155:717-721.
Cohen FE, Sater B, Feingold KR. Potential danger of extending
SMBG techniques to hospital wards. Diabetes Care 1986;9:320322:
22. Langer O, Mazze RS. Diabetes in pregnancy: evaluating self-monitoring performance and glycemic control with memory-based
reflectance meters. Am J Obstet Gynecol 1986;155:635-637.
23. Eriksson KF, Fex G, Trell E. Capillary-venous differences in blood
glucose values during oral glucose tolerance test. Clin Chem
1983;29:993.
A.J.C.P. • February 1991