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CLSI EP25-A: Evaluation of Stability of In Vitro Diagnostic Reagents, 1st Edition
L. Test Principle:
The Lucica Glycated Albumin-L provides quantitative measurement of glycated albumin
based on an enzymatic method and quantitative albumin measurement by a colorimetric
assay. The glycated albumin value (mmol/mol) is automatically calculated by the test
system using the glycated albumin concentration (µmol/L) and the albumin concentration
(µmol/L).
Measurement of glycated albumin:
The serum sample reacts with a ketoamine oxidase to eliminate endogenous glycated
amino acids. The generated hydrogen peroxide is converted to H
2
O by reaction with
peroxidase and hydrogen donor (N, N-Bis (4-sulfobutyl)-3-methylaniline disodium salt).
The treated solution reacts with an albumin-specific protease, which converts glycated
albumin to glycated amino acids. The glycated amino acids react with a ketoamine
oxidase to form glucosone, amino acids, and hydrogen peroxide. The generated hydrogen
peroxide reacts with peroxidase in the presence of N, N-Bis (4-sulfobutyl)-3-
methylaniline disodium salt and 4-aminoantipyrine (4-AA) forming a blue-purple
pigment. Measurement of the absorbance of this blue-purple pigment quantifies the
glycated amino acids produced by glycated albumin.
Measurement of albumin:
The serum sample reacts with the pretreatment solution to convert reduced albumin to
oxidized albumin. The treated solution reacts with bromocresol purple, forming a blue
conjugate of albumin and bromocresol purple. The absorbance of this blue conjugate is
measured to quantify albumin concentration.
M. Performance Characteristics (if/when applicable):
1. Analytical performance:
a. Precision/Reproducibility:
An internal precision study and a multisite precision study at three centers were
performed. Precision studies used three levels of glycated albumin (GA) controls, a
human serum albumin (HSA) pool with a low glycated albumin value, and five native
serum pools. For the internal precision studies, samples were tested with 2 runs per
day, 2 replicates per run over 20 days. Results from different lots were similar.
The precision summary table of glycated albumin values (mmol/mol) for the internal
precision study is shown below.