Interlaboratory Comparison of Enzymatic Methods for Serum Glucose Determination

Abstract

This report describes an interlaboratory comparison of enzymatic serum glucose methods as currently applied in several instrumental adaptations. Four spectrophotometric, hexokinase-based methods used with the Du Pont "aca," the Abbott "Bichromatic Analyzer," the Aminco "Rotochem," and the Technicon "AutoAnalyzer II" were compared with glucose oxidase-based methods as used with the Beckman "Glucose Analyzer" and the "AutoAnalyzer II." We analyzed both normal samples and samples that contained potential interfering substances or were otherwise abnormal. Although all methods were satisfactorily precise, methodological bias was noted in several cases, particularly with abnormal specimens. The hexokinase-based methods were generally more variable. The most consistent data were obtained from the two glucose oxidase methods and the Du Pont aca. Results of this study comprises part of the background information required for development of an accurate glucose reference method under the auspices of the AACC Standards Committee.

Precision and accuracy of blood glucose measurements using three different instruments

“…In contrast to the YSI, the BMG has also been evaluated against other laboratory instruments using the hexokinase method and was found to yield more stable results particularly in abnormal samples (i.e. hemolysis, bilirubin) [4]. As BMG, YSI and EKF instruments do not use photometrical detection, these methods are not affected by turbidities or chromophoric substances like bilirubin or hemoglobin (personal communication with manufacturers).…”

“…From the late 1970s on, the Glucose analyzer II (BMG) by Beckman Instruments has been used as a reference method for the analysis of glucose concentrations employing the glucose oxidase method in heparinized plasma [4]. The YSI 2300 instrument (YSI) from Yellow Springs Instruments Co. uses the same principle but in contrast to the BMG, is capable to measure both whole blood and plasma samples.…”

Fasting Plasma Glucose (FPG) and the Risk of Impaired Glucose Tolerance in Obese Children and Adolescents

“…In fact, although FPG, FSI, and HOMA IR could be indifferently proposed as potential parameters to select obese children at higher risk of IGT, the chance of using the same FPG threshold for both genders despite pubertal stage makes FPG preferable. Other advantages are (i) the widespread availability of plasma glucose measurements in all laboratories; (ii) the lower interlaboratory variability of measuring plasma glucose rather than serum insulin; and (iii) the lower cost of measuring plasma glucose than serum insulin (29,30,31).…”

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“…Oxidative coupling of hydrogen peroxide with 4 Amino-antipyrine (4-AAP) and phenol produces quinoeimine, a red colored dye which is measured at 520 nm. The color intensity is directly proportional to the amount of glucose released by the sample 26 The absorbance was read at 520nm using an ELISA reader against Millipore water (100 µL) as blank.…”

“…The glucose released by the cortisol-induced liver is estimated using glucose oxidase reagent. The percentage of the glucose released was also estimated 26 . Standard reaction mixtures were prepared as follows -(a) Liver + Saline: 2 mL of normal saline was added to the liver placed in the culture plate.…”