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

Glycated Albumin (GA) has been proposed as a short-term indicator of glycemic homeostasis. The aim of this study is to describe the distribution of GA in a large sample of blood donors from Italy to evaluate whether demographic features, namely age and sex, could influence GA levels and define specific reference limits. The study included 1334 Italian blood donors. GA was measured using an enzymatic method (quantILab Glycated Albumin, IL Werfen, Germany). The upper reference limit (URL) was calculated using the non-parametric percentile method. A modest, although significant, increase of GA was observed in relation to age (p<0.001), especially in males, where the differences were more pronounced (p<0.001 in males, p=0.003 in females). Slight differences were documented based on sex (12% [11.3-12.8] in males; 12.2% [11.4-13.1] in females; p=0.01). After excluding individuals with fasting plasma glucose ≥7 mmol/L, the calculated GA URL was 14.5% (95% CI: 14.3-14.7). Subjects with GA>14.5% presented a mean age of 48.4±12.2 years, 66.7% were males and the mean glucose was 6.88±2.5 mmol/L. GA in Caucasians shows a similar increasing trend at older ages documented in other ethnicities. The definition of the URL in this population could be useful for both clinical studies, which will clarify the role of GA for diagnosing and monitoring diabetes, and will encourage the introduction of GA in clinical practice.