Analysis: Serum Fructosamine as a Screening Test for Type 2 Diabetes

537 APPROXIMATELY 5.4 million Americans have type 2 diabetes and do not know it.1 At an early stage, this disease is asymptomatic. If patients with early type 2 diabetes fail to receive treatment at an early stage of the disease, then they are at increased risk of developing end organ disease of the kidneys, eyes, nerves, and heart. Early detection and initiation of treatment of type 2 diabetes can decrease the burden to society of this disease, in terms of both human suffering and financial costs. Screening programs, using a variety of inexpensive and simple tests, have been developed for mass screenings at healthfairs or at a workplace to identify individuals who are at particularly high risk of developing type 2 diabetes. The identified individuals are then invited to be tested with a rigorous diagnostic test, such as a fasting plasma glucose test or a 75-gram oral glucose tolerance to determine whether type 2 diabetes is truly present. In this issue, Carter and his associates have presented evidence supporting the use of a combination of both blood glucose and blood fructosamine screening with a portable meter for poor glycemic control.2 Glucose binds to serum proteins in a nonenzymatic reaction which occurs in proportion to the prevailing serum glucose concentration during the lifespan of each protein. This nonenzymatic reaction is known as glycation, and the product is a glycated protein. The glycation process occurs between glucose and a protein’s amino terminus or an amino acid on a side chain, such as lysine. Measurement of a glycated protein can serve as an index of the magnitude of the mean blood glucose level during the lifespan of that protein.3 The best known glycated protein test is Hemoglobin A1c, also known as glycated hemoglobin, glycosylated hemoglobin, and glycohemoglobin, which refers to a stable hemoglobin component formed slowly by a nonenzymatic reaction between glucose and hemoglobin. The Hemoglobin A1c level is determined by the average blood glucose level over the lifespan of an erythrocyte, which is 120 days. In practice the concentration of this analyte reflects the magnitude of glycemic control over the previous 2–3 months.4 Hemoglobin A1c is a widely used test for monitoring control and adjusting therapy in diabetes. Its use as a diagnostic test for diabetes is controversial. An elevated Hemoglobin A1c level is highly specific but insensitive for detecting diabetes.5 The term “fructosamine” refers to the sum of all ketoamine linkages between circulating glucose and serum proteins. This substance does not contain fructose; however, the glucose chain, which is linked to the protein amino group in a ketoamine bond, becomes modified to resemble the open-chain form of fructose. All serum proteins can become glycated, and