In diabetes, maintaining a normal blood glucose is essential to preventing many medical complications, including heart attacks, diabetic nephropathy, diabetic neuropathy and also diabetic retinopathy eventually leading to blindness. Most commonly, blood sugars are measured by either blood glucose monitoring which measures the current blood glucose level, or by Glycated hemoglobin which measures average glucose levels over approximately 3 months.In a similar way to hemoglobin A1c testing, fructosamine testing determines the fraction of total serum proteins that have undergone glycation. Since albumin is the most abundant protein in blood, fructosamine levels typically reflect albumin glycation.. Because albumin has a half-life of approximately 20 days, the plasma fructosamine concentration reflects relatively recent changes in blood glucose. In patients with diseases that reduce red blood cell lifespan, such as hemolytic anaemia or hemoglobinopathies such as sickle-cell disease, a hemoglobin-based A1c test can be misleadingly low. A1c results may also be falsely high or low in hemoglobinopathies because abnormal hemoglobin variants can interfere in the analysis. In these cases, fructosamine measurement can be used as a marker of blood sugar levels, as its measurements are based on albumin instead of hemoglobin. However, any condition that changes serum albumin will affect the fructosamine result. In practice, fructosamine is rarely measured clinically due to a number of pragmatic concerns. First, diabetes care is rarely changed in short intervals, since diabetes medications can take months to reach a steady state. An exception to this is pregnancy, where medication needs can change more rapidly and fructosamine may help provide closer short-term monitoring. Second, fructosamine has higher variability than A1c tests. Third, the overwhelming majority of studies in diabetes care are based on A1c measurements, which can make fructosamine results difficult to interpret. Fourth, the A1c test is very well standardized and trusted due to its nearly universal use. A variety of more advanced forms of the A1c test can more accurately assay A1c levels during complex hemoglobinopathies and other conditions. However this does not overcome the effect of shortened red blood cell lifespan on A1c results.
Because glycated albumin has a shorter half-life than glycated hemoglobin, glycated albumin reflects recent glycemic control more accurately and usefully for monitoring patients with diabetic end stage renal disease . It can be used less often than blood sugar testing. An average blood glucose level of 155–160 mg/dL could be matched to a GA value of 18–19% in patients with ESRD. The ratio of GA/HbA1c is 3.0 approximately.
Interpretation of results
There is no standard reference range available for this test. The reference values depends upon the factors of patient age, gender, sample population, and test method. Hence, each laboratory report will include the patient's specific reference range for the test. An increase in fructosamine in lab testing results usually means an increase in glucose in the blood. On average, each change of 3.3 mmol in average blood sugar levels will give rise to changes of 1% HbA1c and 75 µmol fructosamine values. However, this overemphasizes the upper-limit of many laboratories' reference ranges of 285 μmol/L as equivalent to HbA1c 7.5% rather than 6.5%. A comparative study, which has been used in official advice for Quality and Outcomes Framework guidance in the UK and summarized by the United States' National Quality Measures Clearinghouse: gives the following formula and resulting values:
