Committee on Diabetes Mellitus Indices of the Japan Society of Clinical Chemistry-recommended reference measurement procedure and reference materials for glycated albumin determination

Abstract

Background: Glycated albumin is an intermediate glycaemic control marker for which there are several measurement procedures with entirely different reference intervals. We have developed a reference measurement procedure for the purpose of standardizing glycated albumin measurements. Methods: The isotope dilution liquid chromatography/tandem mass spectrometry method was developed as a reference measurement procedure for glycated albumin. The stable isotopes of lysine and fructosyl-lysine, which serve as an internal standard, were added to albumin isolated from serum, followed by hydrogenation. After hydrolysis of albumin with hot hydrochloric acid, the liberated lysine and fructosyl-lysine were measured by liquid chromatography/tandem mass spectrometry, and their concentrations were determined from each isotope ratio. The reference materials (JCCRM611) for determining of glycated albumin were prepared from pooled patient blood samples. Results: The isotope dilution-tandem mass spectrometry calibration curve of fructosyl-lysine and lysine showed good linearity (r ¼ 0.999). The inter-assay and intra-assay coefficient of variation values of glycated albumin measurement were 1.2 and 1.4%, respectively. The glycated albumin values of serum in patients with diabetes assessed through the use of this method showed a good relationship with routine measurement procedures (r ¼ 0.997). The relationship of glycated albumin values of the reference material (JCCRM611) between these two methods was the same as the relationship with the patient serum samples. Conclusion: The Committee on Diabetes Mellitus Indices of the Japan Society of Clinical Chemistry recommends the isotope dilution liquid chromatography/tandem mass spectrometry method as a reference measurement procedure, and JCCRM611 as a certified reference material for glycated albumin measurement. In addition, we recommend the traceability system for glycated albumin measurement.

Definition of the upper reference limit of glycated albumin in blood donors from Italy

“…The use of an enzymatic-colorimetric assay allows the high-throughput measurement of GA because it is performed on the same sample used for routine clinical chemistry tests, and with analyzers commonly used in clinical laboratories. The standardization of the method for GA and the definition of biological variability have been recently achieved [10,15]; however, no large studies on a reference Caucasian population have been published yet. Moreover, before introducing GA in clinical practice, it is important to define specific reference limits and the potential influence of age and sex on its distribution in a reference population.…”

“…This assay measures total albumin and the glycated amino acids originated from the proteolytic degradation of glycated albumin simultaneously. GA concentration is reported as a percentage of the total albumin, and corrected with the inter-method arithmetic expression designed to adhere to the GA levels determined with HPLC [10]. Imprecision of the assay was evaluated analyzing two samples, at the concentrations of 15.2% and 32.1%, respectively, 20 times in the same run (within-run CV %), and repeated for 15 days (between-run CV %).…”

“…Glycated albumin (GA) has been proposed as a short-term indicator of glycemic homeostasis, given that albumin turnover is about 20 days [8]. Recently, a colorimetric-enzymatic method has been developed to assess circulating levels of GA on automated analyzers, commonly used for the measurement of clinical chemistry traditional test [9,10]. GA has been introduced in Japan for blood donor screenings as an effective indicator for individuals at risk of developing diabetes [11].…”

Analytical Performances of an Enzymatic Assay for the Measurement of Glycated Albumin

“…The Japan Clinical Chemistry Reference Material (JCCRM) 611 is certified reference material for measurement of GA% in human serum and is available through the ReCCS (Reference Material Institute for Clinical Chemistry Standards) according to the Japan Society of Clinical Chemistry recommendation (17). This material is titrated with isotope dilution-mass spectrometry and provided in liquid frozen vials (3 levels).…”

“…This material is titrated with isotope dilution-mass spectrometry and provided in liquid frozen vials (3 levels). It is the current highest level of traceability for GA determination according to the Committee on Diabetes Mellitus Indices of the Japan Society of Clinical Chemistry (17).…”