What is Glycated Albumin?
Glycated albumin, also known as fructosamine, refers to albumin that has been bound to glucose in the blood through a non-enzymatic reaction called glycation. Albumin is the most abundant protein found in blood plasma and serves as a transport molecule for various substances including fatty acids, hormones, and metal ions. Under normal conditions, a small percentage of albumin circulating in the blood undergoes glycation as glucose binds to its free amino groups. However, in conditions of hyperglycemia such as diabetes mellitus, there is a significant rise in the levels of glycated albumin as more glucose binds to albumin over time.
How is Glycated Albumin Formation Regulated?
The rate of glycated albumin formation is directly proportional to the blood glucose concentration and the lifespan of albumin in the circulation. On average, albumin survives for around 20 days in the blood before being removed and new albumin is synthesized. This lengthy lifespan allows albumin to reliably reflect average blood glucose levels over the past 2-3 weeks. In comparison, hemoglobin A1c (HbA1c) reflects average glucose levels over the past 2-3 months due to the lifespan of red blood cells. Thus, measuring glycated albumin provides a shorter term indication of glycemic control compared to HbA1c.
Significance of Glycated Albumin Assay
Glycated Albumin Assay is an alternate method for monitoring long term glycemia in patients with diabetes besides HbA1c testing. It has several clinical applications:
- Identifying fluctuations in blood glucose: As it reflects shorter term glycemic control, glycated albumin is more sensitive in catching post-prandial fluctuations or day-to-day variations in blood sugar levels compared to HbA1c.
- Diagnosing gestational diabetes: HbA1c levels are not reliable for diagnosing gestational diabetes as pregnancy itself causes changes in red blood cell turnover. Glycated albumin assay is unaffected.
- Monitoring patients on hemodialysis: HbA1c levels are unreliable in end-stage renal disease patients requiring dialysis due to altered red blood cell kinetics. Glycated albumin provides a better indication of glycemic control in these individuals.
- Detecting fructosamine mimetic conditions: Rare genetic disorders or other clinical conditions can artificially lower HbA1c independently of glycemia. Glycated albumin is not affected in such situations.
How is the Glycated Albumin Assay Performed?
Similar to HbA1c testing, the glycated albumin assay involves measuring the binding of glucose to albumin using blood samples. The two common methods used are:
1. Colorimetric/enzymatic assay: This assay utilizes albumin-specific protease to break the albumin-glucose bond and release glycated albumin. An enzyme then reacts with the freed glucose to generate color. The color intensity directly relates to glycated albumin level.
2. E lectrophoresis assay: Here, serum proteins are separated according to electrical charge using capillary electrophoresis. Glycated albumin migrates at a distinct position from nonglycated albumin and can be precisely quantified.
Both assays are highly specific, simple to perform and generate glycated albumin results as a percentage of total albumin or as absolute concentrations in a unit of mmol/L. A reference range of 11.0-16.0% is considered normal.
In Conclusion, the glycated albumin assay serves as a useful adjunct to HbA1c testing for optimally managing diabetes and prediabetes. It provides a shorter term indication of glycemic exposure that is particularly valuable when fluctuations are of clinical importance. With standardization of analytic methods, glycated albumin is gaining acceptance as a reliable marker for routine monitoring of glycemic control.
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