HbA1c and the diagnosis of diabetes mellitus

On-chip, aptamer-based sandwich assay for detection of glycated hemoglobins via magnetic beads

Diabetes can be diagnosed and monitored by measurement of the cutoff ratio between glycated hemoglobins (HbA1c) and total hemoglobin (Hb), which does not require a fasting blood sample and is less influenced by biological variations. In this study, we combined the advantages of the microfluidic system and the selected low-cost, stable and specific aptamers and developed an integrated, aptamer-based microfluidic system for automatic glycated hemoglobin measurements. The detection process of human whole blood can be totally automated in this integrated microfluidic system. According to the experimental results, when compared to conventional bench-top manual assays, reagent consumption was significantly reduced by 75%, and the analysis time was reduced from 3.5h to 30 min. Besides, the novelty in this research also lies in the simultaneously performed two parallel assays for detection of Hb and HbA1c in a single chip. Therefore, this sensitive and low-cost aptamer-based microfluidic system may become a promising tool for point-of -care diagnosis of diabetes.

Prevalence of hyperglycaemia and undiagnosed diabetes mellitus in patients with acute myocardial infarction

The prevalence of hyperglycaemia and undiagnosed diabetes mellitus was assessed in 214 consecutive patients admitted to the coronary care units with acute myocardial infarction (AMI). On admission, 16 patients (7.5%) had known diabetes, and 19 patients, not previously known to be diabetic, had blood glucose concentrations of greater than or equal to 9 mmol/l. Fifteen patients survived for 2 months at which time a 75 g oral glucose tolerance test showed diabetes in 9 (60%) and impaired glucose tolerance in 4 (27%). Ten of these 13 patients (77%) with abnormal glucose tolerance had elevated glycosylated haemoglobin (HbA1c) on admission, indicating pre-existing glucose intolerance or diabetes. The prevalence of undiagnosed diabetes was 4.5% (9/198). However, we may have overlooked undiagnosed diabetes in a small number of patients on admission, since only a random blood glucose less than 8 mmol/l rules out diabetes, WHO criteria. Elevated blood glucose in patients with AMI is more likely to reflect a stationary pre-existing abnormal glucose tolerance than a temporary stress-induced phenomenon.

Hospital management of diabetes

The degree of hyperglycemia may be an important predictor of morbidity and mortality among patients with MI or stroke, and in those undergoing surgical procedures including coronary artery bypass. Hyperglycemia should be aggressively controlled from the time of hospital admission regardless of the patient's primary medical problem or previous diabetes status. Innovative systems for monitoring glucose and for delivering insulin coupled with new pharmacologic therapy, such as long-acting insulin analogues, may help reduce the morbidity and mortality occurring in the estimated 6 million annual hospitalizations that are accompanied by hyperglycemia in the United States.

A nation-wide cross-sectional study of glycosylated haemoglobin in Danish children with type 1 diabetes

A nation-wide screening for HbA1c was carried out in Denmark. Twenty-one paediatric departments treating children with Type 1 diabetes participated. During a period of 4 months 884 children were included, 93% of all those followed at these centres, representing approximately 70-80% of all children and adolescents with Type 1 diabetes in Denmark. Among the children 351 were less than or equal to 12 years and 533 were adolescents between 12 and 18 years. Children less than or equal to 12 years had a HbA1c concentration of 8.9 +/- 1.5 (+/- SD)% and an insulin dose of 0.71 +/- 0.3 U kg-1 24-h-1. For adolescents HbA1c was significantly higher 9.7 +/- 2.0% (p less than 0.001) and insulin dose significantly increased 0.85 +/- 0.3 U kg-1 24-h-1 (p less than 0.001). Normal range for HbA1c is 4.0-6.5 (mean 5.3)% of total haemoglobin. Boys and girls less than or equal to 12 years had similar HbA1c, but girls received 13% more insulin (p less than 0.001). In the group of adolescents, girls had a HbA1c 4% higher than boys (9.9 +/- 2.0 vs 9.5 +/- 2.0%, p less than 0.025), received 11% more insulin (p less than 0.001), and had 6% higher body mass index (p less than 0.001). A weak correlation was found between insulin dose and the HbA1c level (r = 0.29, p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

The diabetic kidney: from hyperfiltration and microalbuminuria to end-stage renal failure

This article describes many new concepts within the area of diabetic renal involvement and diabetic renal disease. Considerable progress has taken place within this area, not only regarding diagnosis of early diabetic nephropathy but also the early treatment of nephropathy in its incipient stage.

The glycohaemoglobin assay as a screening test for diabetes mellitus: the Islington Diabetes Survey

Blood glucose 2 h after an oral glucose load (2hBG) and glycohaemoglobin (GHb) (Corning agar-gel electrophoresis) levels were used as screening tests in a general practice diabetic screening programme. The diagnosis of diabetes (DM) was based on a separate oral glucose tolerance test (OGTT) in 223 of 1040 screened subjects, selected as a stratified sample biased towards higher levels of 2hBG and GHb. The GHb assay was also repeated at the recall examination and urine was tested for glycosuria before and after glucose administration. At a cut-off level of 8.1%, the screening GHb assay correctly identified 90% of all probable diabetics with a specificity of 85.3% (95% Cl 83.3-87.3%) and a positive predictive value of 14.0% (9.0-19.0%). The specificity of the screening GHb assay as a screening test for true DM was 45.8% (39.0-52.4%) at 90% sensitivity, and that of the recall GHb assay was 64.5% (57.9-71.1%). The screening 2hBG was 93.3% (88.9-97.7%) specific at 90% sensitivity as a screening test for true DM diagnosed by OGTT at recall. The test characteristics for fasting glycosuria were: sensitivity 16.7% (0-37.8%) and specificity 98.0% (96.0-100.0%). Equivalent values for the post-glucose test for glycosuria were: 72.7% (46.4-99.0%) and 77.4% (70.1-84.7%), respectively. While GHb assay is a poorer screening test for DM than the 2hBG at the single cut-off level quoted, comparison of the accuracy of the two tests shows that the GHb assay is only marginally less accurate. It is superior to testing for glycosuria as a screening test for DM and can be performed on any random blood sample, facilitating its use in population screening.

Prevalence and risks of hyperglycaemia and undiagnosed diabetes in patients with acute myocardial infarction

Two studies were undertaken to assess the prevalence of undiagnosed diabetes mellitus in patients admitted with acute myocardial infarction (AMI), and the effect of diabetes mellitus and admission hyperglycaemia on outcome. In the retrospective study, admission levels of plasma glucose (APG) were higher (p less than 0.02) in patients dying from cardiogenic shock than in survivors, but they were not related to infarct size. In the prospective study APG was related (p less than 0.01) to concurrent levels of glycosylated haemoglobin (HbA1c), which were in turn related to outcome--the mortality rate was 23% for those with normal HbA1c (less than 7.5%), 33% for those with borderline abnormal HbA1c (7.5-8.5%), and 63% for those with clearly abnormal HbA1c (greater than 8.5%). Cardiogenic shock was commoner in the groups with higher HbA1c levels. In addition, admission hyperglycaemia was associated (p less than 0.01) with the incidence of cardiogenic shock even after correcting for the effects of HbA1c. All of the survivors from the clearly abnormal HbA1c group, but none of those from other groups, were diabetic at follow up, suggesting an overall prevalence of undiagnosed diabetes mellitus of 5.3%. The contribution of undiagnosed diabetes mellitus to total mortality following AMI seems at present to be underestimated.

Glycosylated haemoglobins: biochemical evaluation and clinical utility

A review is given of the biochemical background of the glycosylated haemoglobins, their methods of determination, and their clinical significance. Special attention is paid to the sample preparation. For all methods except the colorimetric TBA-method, the removal of the labile pre-HbA1c fraction is essential. Under proper conditions, high-performance liquid chromatography, agar-gel electrophoresis and affinity chromatography are suitable methods for use in the clinical laboratory for the estimation of HbA1c and HbA1. However, the colorimetric TBA-method must be considered to be the method of choice. The clinical utility of the test is stressed with special respect to the management of diabetic pregnancies, the control of home-monitoring of blood glucose, and the objective measurement of the effect of changing diabetic therapy.

Characteristics of labile HbA1 in erythrocytes from normals and diabetics

Incubation of erythrocytes from diabetic patients and non-diabetic persons in 0.15 mol/l saline at 37 degrees C was followed by a decrease in ion-exchange microcolumn determined HbA1 only during the first 4 h. The fraction removed was denoted as labile HbA1 and the remaining fraction as stable HbA1. Incubation in saline overnight at 20 degrees C did not completely remove the labile fraction. Incubation in saline overnight at 4 degrees C yielded only a slight decrease in labile HbA1. Incubation in saline containing various glucose concentrations (up to 100 mmol/l) produced increasing amounts of HbA1 during the first 3-4 h after which an equilibrium was reached. In both normal and diabetic erythrocytes incubated for 3-4 h we found a linear relationship between changes in labile HbA1 and glucose concentration. The degree of increase in labile HbA1 was the same in normals and diabetics and not dependent on pre-existing normal or moderately increased stable HbA1. In the blood from non-diabetics (n = 30) labile HbA1 was 0.5 +/- 0.3% (mean +/- SD) and in diabetics (n = 80) 1.6 +/- 0.8%. The correlation between labile HbA1 and simultaneously determined blood glucose was r = 0.72.