Determining Stability of Stored Samples Retrospectively: The Validation of Glycated Albumin

Abstract

BACKGROUND:Determining the stability of stored samples for assays that were not available at the time of original collection is problematic. To assess sample stability for a relatively new assay of glycated albumin (GA), we first measured GA in fresh samples and in samples stored for 19 -23 years. We then compared the regression of the contemporaneous glycohemoglobin (Hb A 1c ) values against the GA results from fresh vs stored samples, reasoning that similar slopes and intercepts would provide strong, albeit indirect, support for the stability of the stored samples for GA measurements.

A newer conversion equation for the correlation between HbA1c and glycated albumin

“…The high correlation between HbA1c and GA is well known [23]. Our results are consistent with Tahara's findings.…”

Utility of glycated albumin for the diagnosis of diabetes mellitus in a Japanese population study: results from the Kyushu and Okinawa Population Study (KOPS)

“…This assay uses a glycated amino acid elimination reaction for an improved enzymatic glycated albumin measurement assay, which has correlated very highly (r=0.99) with values for glycated albumin obtained by HPLC assay [14]. The assay is stable even for samples stored for a long period of time (frozen for 19-23 years) [22]. Although the actual CVs for the automated assay had no international reference standard or reference method, the assay had intra-assay and interassay CVs of 1.1% and 1.6%, respectively, in laboratories at both Tufts University and Asahi Kasei Pharma.…”

“…Plasma HDLcholesterol was measured using a direct homogenous assay of the plasma using detergents (Determiner L HDL-C, Kyowa Medex). The Lipid Metabolism Laboratory maintains lipid standardisation with the Centers for Disease Control, Atlanta, Georgia, for these assays, and intra-assay and inter-assay CVs were less than 2% [13,22].…”

Recent Topics in Chemical and Clinical Research on Glycated Albumin

“…The analysis of stored GA from past large-scale cohort studies are also starting to be published, 24 after confirmation that GA can be measured in stored samples. 25,26 An analysis of stored samples from the Diabetes Control and Complications Trial (DCCT) published in 2014 25 showed that GA was associated with diabetic retinopathy and nephropathy to the same extent as HbA1c.…”

“…15,16 Moreover, in late pregnancy, iron-deficiency anemia has the effect of raising HbA1c levels but does not affect GA levels. 17,18 Thus, original researches on GA in vitro [19][20][21][22][23] or clinical usage [24][25][26][27] and review articles of GA [28][29][30][31] have recently increased whereas HbA1c has a long history of research.…”