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.

We describe the interlaboratory testing of a candidate Reference Method (Part I) for uric acid in serum. The method is based on the ultrasound spectrophotometric quantitation of uric acid before and after incubation with uricase. A comprehensive investigation involving 12 laboratories was organized to document the transferability, intra- and interlaboratory precision, and general reliability of the candidate Reference Method. The interlaboratory CV with this method was about 2 to 6% for uric acid concentrations ranging from 0.12 to 0.60 mmol/L. The results detailed here demonstrate that the method can be successfully duplicated among different laboratories.

Sensitivity and specificity of three methods (random urine glucose (RUG) > 25 mg. per deciliter; positive Clinitest; and random plasma glucose (RPG) > 140, > 120, and > 100 mg. per deciliter) for detecting the unknown diabetic were compared. In 1,952 screenees, RUG of 96.7 per cent was 3 to 25 mg. per deciliter (normoglucosuria), RUG of 2.0 per cent was 26 to 100 mg. per deciliter (moderate hyperglucosuria), and of 1.3 per cent was > 100 mg. per deciliter (marked hyperglucosuria). Twenty-five randomly selected from each of the first two groups and 18 from the third group had a glucose tolerance test (GTT); seven in the third group had fasting plasma glucose tests > 150 mg. per deciliter. GTTs were evaluated by United States Public Health Service (USPHS), Fajans-Conn (F-C), and summation (S) criteria, and tested screenees divided into nondiabetic (ND) and diabetic (DM). NDs with RUG > 25 mg. per deciliter were false positive screens: renal hyperglucosurics (RHG) if GTT urine glucose ^ 80 mg. per deciliter, nonrenal hyperglucosurics (NRHG) if GTT urine glucose *£ 25 mg. per deciliter. The prevalence of DM was 1.24 per cent (USPHS), 1.37 per cent (F-C), and 1.45 per cent (S). The prevalence of false positives (USPHS) was 2.04 per cent (1.19 per cent RHG and 0.85 per cent NRHG). In the normogluco. uria group, 100 per cent who had a GTT were true negatives. In the moderate hyperglucosuria group, 16 per cent (USPHS) were true positives, 84 per cent false positives (44 per cent RHG, 40 per cent NRHG). In the marked hyperglucosuria group, 72 per cent (USPHS) were true positives, 28 per cent false positives (24 per cent RHG and 4 per cent NRHG). By Clinitest, 23 per cent of the DMs (USPHS) were false negatives, and 1.8 per cent in the normoglucosuria group were false positives. Nine per cent of the DMs were false negatives by RPG > 140, and 4.5 per cent were false negatives by RPG > 120. RUG > 25 mg. per deciliter was as sensitive as the GTT in detecting unknown DMs but was less specific. Random normoglucosuric screenees are unlikely to have diabetes; about 40 per cent of random hyperglucosuric screenees have diabetes. DIABETES 27:810-16, August, 1978.Methods commonly used to determine urine glucose are either insensitive and nonspecific (Clinitest) or sensitive and relatively specific but not quantitative (Clinistix, Keto-diastix, Tes-Tape). 1>2 It has been recommended that diabetes screening be done using more sensitive and specific plasma glucose measurements, preferably after a glucose load. 3 Unfortunately, such methods involve blood collection; thus, they are invasive, expensive, and slow. For this reason, there appears to be an unmet need for a reliable urine screening technique for diabetes, with the method being glucose specific, sensitive, noninvasive, inexpensive, and rapid.Two specific enzymatic methods-glucose oxidase 4 ' 6 and hexokinase 5 -have been developed to measure glucose in blood, plasma, and urine. The original glucose oxidase procedure 4 was colorimetric and measured hydrogen peroxide formation. Si...

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