Acta Med Scand 200: 297-299, 1976
Serum Glucose Determination with Dextrostix and the Eyetone Reflectance Meter P. Hornnes and C. Kuhl From the Department of Internal Medicine T , Bispebjerg Hospital, University of Copenhagen, Copenhagen, Denmark
ABSTRACT. A simple, modified procedure for the Dextrostix-Eyetone system has been evaluated in order to enable the system to measure the concentration of glucose in serum as well as in whole blood. A reduction of the ordinary time of reaction on the Dextrostix from 60 to 45 sec gave serum glucose determinations by the Dextrostix-Eyetone system that correlated almost perfectly with those obtained by a specific conventional laboratory procedure. Thus, the coefficient of correlation was 0.99 and the regression line very close to the ideal line. As the modification is very simple and does not involve any changes in the adjustment of the instrument, it is recommendable in all cases where only serum samples are available.
Blood glucose determination by the DextrostixEyetone system is a precise and reliable alternative to conventional laboratory methods (2). In the performance of the ordinary Dextrostix-Eyetone procedure, a sample of whole blood is required, the sample being transferred to the Dextrostix by means of a pipette, or, even more easily, by dipping the strip into the sample (1). For many hospital and laboratory purposes serum is, however, a preferable medium to whole blood and, furthermore, serum may be stored deep-frozen for later analysis. The practical value of the Eyetone measuring device would hence be considerably increased if it could also be applied to serum samples. The aim of the present investigation was to evaluate a modification of the current operating procedure for the Dextrostix-Eyetone system in order to enable the system to work with serum as a substrate.
MATERIAL AND METHODS Serum samples were obtained from patients submitted to glucose tolerance tests or insulin-hypoglycemia tests for other reasons. Hyperglycemic samples were also prepared by adding a concentrated aqueous glucose solution. In a preliminary study, 34 serum samples were analysed in duplicate by the conventional 60-second Dextrostix-Eyetone procedure. As the results did not compare satisfactorily with those obtained by a glucose oxidase reference method (3). new series of experiments were initiated in order to investigate if changes in the time of reaction on the Dextrostix might improve the performance of the system. A 15-second reduction of the time of reaction appeared to yield almost correct results. Consequently, 90 serum samples were analysed in duplicate by the reference method (3) as well as by the Dextrostix-Eyetone procedure, allowing a 45-second time of reaction only. Otherwise the measuring was done in close accordance with the operating manual. Serum was applied to the reagent area of the strip by means of a pipette. Orthogonal regression analysis was applied to test the correlation between serum glucose concentrations obtained by the reference method and the DextrostixEyetone procedure. Analysis of variance was used for comparing the precisions of the methods. The significance of differences between variances was tested by means of the F-test. P-values less than 0.05 were considered significant.
RESULTS Fig. 1 shows concentrations of serum glucose obtained by the Dextrostix-Eyetone system using a 60-second reaction time and the reference method. The coefficient of correlation is 0.99, and the regression line y = 1.24~-4.0.Fig. 2 shows that when the time of reaction was reduced to 45 sec, the coefficient of correlation was still very high (0.99) Acta Med Scand 200
298
P . Hornnes and C . Kiihl y ' l 24.x-4 r-099 P'O.001
glucose
mgllOOml
glucose mgl100ml
y = 0 98.X-2 r = 0.99 p 0.001
'
300
300
//,"'
v 0
L
%
W
a8
0
L
W >
45 sec
60sec
,
//
Serum Glucose Determination with Dextrostix and the Eyetone Reflectance Meter P. Hornnes and C. Kuhl From the Department of Internal Medicine T , Bispebjerg Hospital, University of Copenhagen, Copenhagen, Denmark
ABSTRACT. A simple, modified procedure for the Dextrostix-Eyetone system has been evaluated in order to enable the system to measure the concentration of glucose in serum as well as in whole blood. A reduction of the ordinary time of reaction on the Dextrostix from 60 to 45 sec gave serum glucose determinations by the Dextrostix-Eyetone system that correlated almost perfectly with those obtained by a specific conventional laboratory procedure. Thus, the coefficient of correlation was 0.99 and the regression line very close to the ideal line. As the modification is very simple and does not involve any changes in the adjustment of the instrument, it is recommendable in all cases where only serum samples are available.
Blood glucose determination by the DextrostixEyetone system is a precise and reliable alternative to conventional laboratory methods (2). In the performance of the ordinary Dextrostix-Eyetone procedure, a sample of whole blood is required, the sample being transferred to the Dextrostix by means of a pipette, or, even more easily, by dipping the strip into the sample (1). For many hospital and laboratory purposes serum is, however, a preferable medium to whole blood and, furthermore, serum may be stored deep-frozen for later analysis. The practical value of the Eyetone measuring device would hence be considerably increased if it could also be applied to serum samples. The aim of the present investigation was to evaluate a modification of the current operating procedure for the Dextrostix-Eyetone system in order to enable the system to work with serum as a substrate.
MATERIAL AND METHODS Serum samples were obtained from patients submitted to glucose tolerance tests or insulin-hypoglycemia tests for other reasons. Hyperglycemic samples were also prepared by adding a concentrated aqueous glucose solution. In a preliminary study, 34 serum samples were analysed in duplicate by the conventional 60-second Dextrostix-Eyetone procedure. As the results did not compare satisfactorily with those obtained by a glucose oxidase reference method (3). new series of experiments were initiated in order to investigate if changes in the time of reaction on the Dextrostix might improve the performance of the system. A 15-second reduction of the time of reaction appeared to yield almost correct results. Consequently, 90 serum samples were analysed in duplicate by the reference method (3) as well as by the Dextrostix-Eyetone procedure, allowing a 45-second time of reaction only. Otherwise the measuring was done in close accordance with the operating manual. Serum was applied to the reagent area of the strip by means of a pipette. Orthogonal regression analysis was applied to test the correlation between serum glucose concentrations obtained by the reference method and the DextrostixEyetone procedure. Analysis of variance was used for comparing the precisions of the methods. The significance of differences between variances was tested by means of the F-test. P-values less than 0.05 were considered significant.
RESULTS Fig. 1 shows concentrations of serum glucose obtained by the Dextrostix-Eyetone system using a 60-second reaction time and the reference method. The coefficient of correlation is 0.99, and the regression line y = 1.24~-4.0.Fig. 2 shows that when the time of reaction was reduced to 45 sec, the coefficient of correlation was still very high (0.99) Acta Med Scand 200
298
P . Hornnes and C . Kiihl y ' l 24.x-4 r-099 P'O.001
glucose
mgllOOml
glucose mgl100ml
y = 0 98.X-2 r = 0.99 p 0.001
'
300
300
//,"'
v 0
L
%
W
a8
0
L
W >
45 sec
60sec
,
//
