The clinical utility of glycosylated hemoglobin

A Novel Approach for Glycosylated Hemoglobin Testing Using Microchip Affinity Electrophoresis

OBJECTIVE

Effective management of diabetes largely benefits from early diagnosis followed by intensive long-term regulation of blood glucose. The levels of glycohemoglobin (HbA1 and HbA1c) have been used as standard biomarkers to assess long-term blood glucose concentrations for diabetes diagnosis and management. Gold standard laboratory methods for HbA1 and HbA1c testing are often costly and not widely available. Moreover, currently available point-of-care (POC) immunoassay-based glycohemoglobin tests may produce inaccurate test results for patients with co-existing diseases such as hemoglobin disorders and anemia. Here, we report a POC platform, HemeChip-GHb, for quantitative HbA1 detection leveraging paper-based affinity electrophoresis.

METHODS

We describe the design and development of the HemeChip-GHb test. Feasibility and accuracy of the HemeChip-GHb system were demonstrated by testing blood samples collected from healthy donors, patients with prediabetes, and patients with diabetes.

RESULTS

HbA1 levels measured with HemeChip-GHb show 0.96 correlation to the levels reported from the clinical standard HPLC tests, and with a bias of -0.72% based on Bland-Altman analysis. 99.6% of the HbA1 levels for paired HemeChip-GHb and HPLC fell within A and B zones of no difference in clinical outcome based on error grid analysis.

CONCLUSION

Using HemeChip-GHb we achieved accurate diabetes status detection with sensitivity and specificity of 100%.

SIGNIFICANCE

We presented a novel POC paper-based affinity electrophoresis platform that has the potential for accurately diagnosing diabetes, and addressing an unmet need for accurate and affordable diagnostics in resource-challenged environments.

Impacts of ambient air pollution on glucose metabolism in Korean adults: a Korea National Health and Nutrition Examination Survey study

BACKGROUND

Exposure to air pollution was reported to affect glucose metabolism, increasing the risk of diabetes mellitus. We conducted an epidemiological study on glucose metabolism and air pollution by exploring the levels of fasting blood glucose (FBG) and hemoglobin A1c (HbA1c) with changes in ambient air quality, depending on the characteristics of the susceptible population.

METHODS

We carried out a cross-sectional analysis of a nationally representative sample of 10,014 adults (4267 in male and 5747 in female) from the Korea National Health and Nutrition Examination Survey in 2012 and 2013 along with data from the Korean Air Quality Forecasting System. The analysis was performed using a generalized linear model stratified by sex, age, and presence of diabetes. We assessed the changes in FBG and HbA1c associated with exposures to particulate matter (PM₁₀), fine particulate matter (PM_2.5), and nitrogen dioxide (NO₂) after controlling for confounders.

RESULTS

There were 1110 participants with diabetes (557 in male and 553 in female). Overall, the FBG level increased by 7.83 mg/dL (95% confidence interval [CI]: 2.80-12.87) per interquartile range (IQR) increment of NO₂, 5.32 mg/dL (95% CI: 1.22-9.41) per IQR increment of PM₁₀ at a moving average of 0-6 days, and 4.69 mg/dL (95% CI: 0.48-8.91) per IQR increment of PM_2.5 at a moving average of 0-5 days. HbA1c increased by 0.57% (95% CI: 0.04-1.09) per IQR increment of PM₁₀ at a moving average of 0-60 days and 0.34% (95% CI: 0.04-0.63) per IQR increment of PM_2.5 at a moving average of 0-75 days. The change in FBG and HbA1c increased more in the diabetic group, especially in males aged 65 years or more. There was a strong association between elevation in diabetes-related parameters and exposure to air pollution.

CONCLUSIONS

Our study provides scientific evidence supporting that short- and mid-term exposure to air pollution is associated with changes in biological markers related to diabetes. This finding suggests that the impact of air pollution should be reflected in chronic disease management when establishing local health care policies.

Determination of haemoglobin A1c levels using high-performance liquid chromatography of bloodstains

This study aimed to determine haemoglobin A1c (HbA1c) levels in bloodstains shed on glass and fabric surfaces on specified test dates. Blood samples were taken from 26 patients (13 diabetic and 13 non-diabetic). Initial HbA1c levels were detected by using high-performance liquid chromatography (HPLC), and bloodstains were created on both cotton fabric and glass surfaces. Samples were processed at different ages (0, 7, 14, 28 and 56 days) by diluting distilled water and then measuring HbA1c levels by HPLC again. In all stains, HbA1c levels could be determined by using HPLC, but there was a moderate rise in accordance with the age of the stains. A statistically significant difference was found for bloodstains on clothes compared to those on glass surfaces. Receiver operating curve analysis found a sensitivity of 1.0 and specificity of 0.923 (cut-off 6.55) for glass surfaces on the seventh day; a sensitivity of 1.0, a specificity of 0.846 (cut-off 6.45) for clothes on the seventh day; a sensitivity of 1.0 and a specificity of 0.923 (cut-off 6.85) for clothes on the 56th day; and a sensitivity of 1.0 and a specificity of 0.846 (cut-off 7.55) for glass surfaces on the 56th day. In conclusion, this study found that HbA1c levels could be measured with high reliability from forensic bloodstains by using HPLC. Thus, in cases where DNA data banks cannot identify individuals, it would make sense to turn to those who have a medical history of diabetes among the suspects with the results of high HbA1c levels.

HbA1c-testing: Evaluation of two point-of-care analysers

BACKGROUND

HbA_1c is a critical parameter for the medical management of patients with diabetes mellitus. Interventions that reduce HbA_1c levels lead to a diminution of microvascular complications. For two decades, point of care testing (POCT) methods have been regularly used to measure HbA_1c. The results significantly impact on the management of patients with diabetes mellitus and the accuracy of the results is critical. It is important to know the performance of common methods of HbA_1c measurements in daily life. We, therefore, aimed at evaluating the accuracy of two different analysers especially developed for POCT and compared them to a reference method.

METHODS

We prospectively tested two widely used POCT methods to measure HbA_1c, namely Afinion™ AS100 Analyzer (Axis-Shield, Oslo Norway) and DCA Vantage™ Analyzer (Siemens Healthcare Diagnostics, Tarrytown NY, US) in venous samples of 100 patients. As a reference method, we used the high-performance liquid chromatography method G8 HPLC used in the Biochemistry Laboratory of the Inselspital Bern. The National Glycohaemoglobin Standardization Program (NGSP) has certificated all methods used in this study. The comparability and degree of agreement was assessed using Bland-Altman plot.

RESULTS

The HbA_1c levels ranged from 33 to 116 mmol/mol (5.2-12.8%), 31-122 mmol/mol (5.0-13.3%) and 30-119 mmol/mol (4.9-13%) for Afinion™, DCA Vantage™ and G8 HPLC Analyzer, respectively. The 95% limits of agreement were between -0.84 and +0.30 for the Afinion™ and -0.71 and +0.29 for DCA Vantage™. The results of both POCT were significantly lower with a bias of -0.27% and -0.21% (p < 0.0001) for Afinion™ and DCA Vantage™ Analyzer, respectively.

CONCLUSIONS

The POCT methods tested in this study showed a good correlation with the laboratory reference method, however, with an overall negative bias.

Chebulic acid attenuates ischemia reperfusion induced biochemical alteration in diabetic rats

CONTEXT

Diabetic nephropathy is one of the important microvascular complications of diabetes; however, the main problem remains is the control of progression of nephropathy in diabetes. Chebulic acid was selected, as tannins from Terminalia chebula are used as antidiabetic, renoprotective, antioxidant, hypotensive and an α-glucosidase inhibitor.

OBJECTIVE

In this study, we evaluated the effect of chebulic acid on ischemia reperfusion induced biochemical alteration in diabetic rats.

MATERIALS AND METHODS

Chebulic acid (CA) was isolated from T. chebula; LD(50) and acute toxicity studies of CA were done. Renal ischemia and reperfusion technique was used to induce nephropathy in diabetic rats. Glibenclamide (10 mg/kg) was used as diabetic standard; CA at doses of 25 and 50 mg/kg were administered for 28 days and various biochemical parameters were monitored.

RESULTS

The LD(50) was found to be 251 mg/kg; 25 and 50 mg/kg doses were selected as no toxic symptoms were observed at both doses, except slight diarrhea. CA significantly (p < 0.001) reduced the glucose, creatinine, urea nitrogen, glycosylated hemoglobulin, proteinuria, urine albumin excretion, glomerular filtration rate (GFR), and increased serum insulin and glycogen level. CA also restored glucose 6-phosphate dehydrogenase, glutathione, superoxide dismutase, catalase and malondialdehyde levels. Improvement in kidney was also noted in histopathological studies.

CONCLUSIONS

The statistical data indicated that chebulic acid at both doses (25 and 50 mg/kg) improves biochemical alterations caused by renal ischemia in diabetic rats.

Parameters of haematology, clinical chemistry and lipid metabolism in the common marmoset and alterations under stress conditions

Common marmosets are suitable non-human primate models for many human diseases. Standard values for blood parameters are required to evaluate physiological and pathological situations. Two studies were conducted: study I to determine standard values and study II to examine these under changed housing conditions. In study I, all parameters for clinical chemistry were similar in range for both genders with these specifics: male marmosets had significantly higher total and LDL cholesterol levels than females, whereas the mean corpuscular volume and the mean corpuscular haemoglobin were significantly lower than in females. In study II, glucose, lymphocytes and salivary cortisol were significantly lower, and faecal cortisol was increased during the change of housing conditions. In conclusion, standard values for haematology and clinical chemistry for the common marmoset were determined. Further on, parameters that are influenced by relocation stress and its importance for experimental results are described.

Frequent monitoring of A1C during pregnancy as a treatment tool to guide therapy

OBJECTIVE

No guidelines for A1C measurement exist for women with gestational diabetes mellitus (GDM). The aim of this study was to document the rate of A1C decline in women with GDM.

RESEARCH DESIGN AND METHODS

Women with GDM in the Santa Barbara County Endocrine Clinic are managed with a carbohydrate-restricted diet and self-monitored blood glucose before and 1-h postprandial. Insulin is started if the preprandial glucose concentration is ≥90 mg/dl and/or a 1-h postprandial glucose concentration is ≥120 mg/dl. Capillary A1C was tested weekly using the DCA2000+ analyzer.

RESULTS

Twenty-four women with GDM (aged 29.0 ± 7.3 years) with initial A1C ≥7.0% were recruited. Baseline A1C was 8.8 ± 1.8%. Mean A1C decline was 0.47% per week (range 0.10-1.15%); the maximum was 4.3% in 4 weeks.

CONCLUSIONS

This study documents rapid decline in A1C during pregnancy and the utility of weekly A1C to guide therapy.

Maternal blood glucose in diabetic pregnancies and cognitive performance in offspring in young adulthood: a Danish cohort study

AIMS

Maternal diabetes is a known risk factor for perinatal complications, but there are little data on consequences for long-term intellectual outcome in offspring. We assess cognitive performance in military conscripts according to maternal blood glucose levels during pregnancy.

METHODS

We identified a cohort of 60 Danish male offspring of insulin-treated diabetic mothers born between 1976 and 1984 and followed this cohort to military conscription. From medical records, we extracted data on all available values of maternal blood glucose categorized as fasting and non-fasting and by day in pregnancy, together with maternal White class, smoking habits and socio-economic status. The main outcome was cognitive performance at conscription measured with a validated intelligence test. The association between maternal blood glucose level and cognitive performance was assessed by multivariate linear regression and a fitted fractional polynomial.

RESULTS

Median fasting blood glucose values in the second half of pregnancy was negatively associated with cognitive scores at conscription [adjusted coefficient -1.7; 95% confidence interval (CI) -3.0; -0.4]. Restriction to only first-born sibling slightly strengthened the association (coefficient -1.9; 95% CI -3.3; -0.5), but after exclusion of two pregnancies with the blood glucose > 10 mmol/l the association became insignificant (coefficient -0.6; 95% CI -2.6; 1.4).

CONCLUSIONS

Maternal blood glucose level during diabetic pregnancy is negatively associated with cognitive performance in offspring at military conscription. In pregnancies with fasting blood glucose levels below 10 mmol/l, the association is weak and considered to be without clinical relevance.

Examination of lower targets for low-density lipoprotein cholesterol and blood pressure in diabetes--the Stop Atherosclerosis in Native Diabetics Study (SANDS)

Diabetes incidence is increasing rapidly in the United States. Diabetes increases the risk for cardiovascular disease, the major cause of death in diabetic individuals. The conventional cardiovascular risk factors of hyperlipidemia and hypertension worsen diabetic vascular disease. Treatment targets for low-density lipoprotein cholesterol (LDL-C) and blood pressure in diabetic individuals are being debated. The SANDS is a randomized, open-label, 3-year trial to examine the effects of aggressive LDL-C (goal <70 mg/dL) and blood pressure (BP) (goal <115/75 mm Hg) reduction versus the standard goals of <100 mg/dL for LDL-C and <130/85 mm Hg for BP. Five hundred forty-nine American-Indian men and women >40 years old with type 2 diabetes were randomized to 1 of 2 groups. Lipids and BP are managed using Food and Drug Administration-approved medications in an algorithmic approach. The presence and progression of atherosclerosis are evaluated by carotid ultrasonography; echocardiography assesses cardiac function. The primary end point is the composite outcome of change in carotid artery intimal medial thickness and fatal/nonfatal cardiovascular events. These outcomes are combined by using a ranked analysis for carotid thickness and assigning a "worst rank" for a cardiovascular event. Secondary end points include carotid plaque score, left ventricular geometry and function, serum C-reactive protein, and safety measures. Unique aspects of the study design and analysis plan involve the use of a composite outcome and changes during the trial of LDL-C treatment goals for participants with baseline or incident cardiovascular disease in the conventional group because of changes in the standard of care. Study results will further understanding of the effects of aggressive risk factor reduction on atherosclerosis burden and cardiac function in diabetic individuals in US populations and will help determine optimal LDL-C and BP treatment goals for diabetic patients.

Amadori adducts activate nuclear factor-kappaB-related proinflammatory genes in cultured human peritoneal mesothelial cells

Diabetes mellitus leads to a high incidence of several so-called complications, sharing similar pathophysiological features in several territories. Previous reports points at early nonenzymatic glycosylation products (Amadori adducts) as mediators of diabetic vascular complications. In the present study, we analysed a possible role for Amadori adducts as stimulators of proinflammatory pathways in human peritoneal mesothelial cells (HPMCs). Cultured HPMCs isolated from 13 different patients (mean age 38.7+/-16 years) were exposed to different Amadori adducts, that is, highly glycated haemoglobin (10 nM) and glycated bovine serum albumin (0.25 mg ml(-1)), as well as to their respective low glycosylation controls. Amadori adducts, but not their respective controls, elicited a marked increase of NF-kappaB activation, as determined by electromobility shift assays and transient transfection experiments. Additionally, Amadori adducts significantly increased the production of NF-kappaB-related proinflammatory molecules, including cytokines, such as TNF-alpha, IL-1beta or IL-6, and enzymes, such as cyclooxygenase-2 and inducible nitric oxide (NO) synthase, this latter leading to the release of NO by HPMCs. The effects of Amadori adducts were mediated by different reactive oxygen and nitrosative species (e.g. superoxide anions, hydroxyl radicals, and peroxynitrite), as they were blunted by coincubation with the appropriate scavengers. Furthermore, NO generated upon exposure to Amadori adducts further stimulated NF-kappaB activation, either directly or after combination with superoxide anions to form peroxynitrite. We conclude that Amadori adducts can favour peritoneal inflammation by exacerbating changes in NO synthesis pathway and triggering NF-kappaB-related proinflammatory signals in human mesothelial cells.

Diagnostic accuracy of glycohemoglobin A1c (HbA1c) for postprandial hyperglycemia was equivalent to that of fasting blood glucose

OBJECTIVES

To compare the sensitivity, specificity, and total accuracy of an HbA1c of > or =6.5% in the detection of hyperglycemia (PPHG) relative to those of a fasting blood glucose (FBG) of > or =7.0 mmol/L.

METHODS

A total of 6,010 subjects (2,987 men and 3,023 women) living or working in Kasugai, Japan, underwent a medical checkup at Kasugai City Medical Care Center between April 2001 and March 2002. For the 91 subjects who had either a FBG of > or =7.0 mmol/L or an HbA1c of > or =6.5%, a 75-g oral glucose tolerance test was performed to confirm or exclude PPHG. We calculated the true- and false-positive odds ratios to evaluate the sensitivity and specificity of HbA1c relative to FBG, and compared the overall accuracy by calculating the conditional relative odds ratio (CROR).

RESULTS

Among the 91 subjects, the true- and false-positive odds ratios were 0.43 (95% CI 0.26-0.69) and 0.40 (0.13-1.27) (Fisher's exact test, P < .090), respectively; the CROR was 1.07 (95% CI 0.30-3.75).

CONCLUSIONS

Although the HbA1c test was marginally more specific but less sensitive than the FBG test, at the given cutoff points the accuracies of two tests were equivalent.

An efficient preparation of polyanionic affinity agent and its evaluation for the measurement of glycated hemoglobin

An efficient method was developed for the preparation of polyanionic affinity agent (3), a key component in the measurement of glycated hemoglobin (GHb). Glycated hemoglobin is an important clinical marker for diagnosis of patients with diabetes and useful to monitor the management of disease. The affinity agent (3) was prepared based on coupling reaction between poly(acrylic acid) (1) and 3-aminophenylboronic acid (2) in water. The critical features of this polymeric affinity agent (3), such as size, boronic acid incorporation ratio and concentration, on the measurement of glycated hemoglobin were evaluated. It was found that the agent (3) prepared using poly(acrylic acid) (1) with 225 kDa molecular weight gave optimal GHb measurement. The performance test results demonstrated that the boronic acid incorporation ratio and concentration of affinity agent (3) play a critical role in the assay and determines the precision of glycated hemoglobin measurement.

Glycosylated human oxyhaemoglobin activates nuclear factor-kappaB and activator protein-1 in cultured human aortic smooth muscle

Diabetic vessels undergo structural changes that are linked to a high incidence of cardiovascular diseases. Reactive oxygen species (ROS) mediate cell signalling in the vasculature, where they can promote cell growth and activate redox-regulated transcription factors, like activator protein-1 (AP-1) or nuclear factor-kappaB (NF-kappaB), which are involved in remodelling and inflammation processes. Amadori adducts, formed through nonenzymatic glycosylation, can contribute to ROS formation in diabetes. In this study, we analysed whether Amadori-modified human oxyhaemoglobin, glycosylated at either normal (N-Hb) or elevated (E-Hb) levels, can induce cell growth and activate AP-1 and NF-kappaB in cultured human aortic smooth muscle cells (HASMC). E-Hb (1 nm-1 x microm), but not N-Hb, promoted a concentration-dependent increase in cell size from nanomolar concentrations, although it failed to stimulate HASMC proliferation. At 10 nm, E-Hb stimulated both AP-1 and NF-kappaB activity, as assessed by transient transfection, electromobility shift assays or immunofluorescence staining. The effects of E-Hb resembled those of the proinflammatory cytokine tumour necrosis factor-alpha (TNF-alpha). E-Hb enhanced intracellular superoxide anions content and its effects on HASMC were abolished by different ROS scavengers. In conclusion, E-Hb stimulates growth and activates AP-1 and NF-kappaB in human vascular smooth muscle by redox-sensitive pathways, thus suggesting a possible direct role for Amadori adducts in diabetic vasculopathy.

Ion-exchange microchromatography and thiobarbituric acid colorimetry for the measurement of canine glycated hemoglobins

Nonenzymatic glycation of hemoglobin is a slow, continuous, and irreversible process which takes place during the whole lifespan of the erythrocyte. When hemolytic diseases are ruled out, the levels of glycated hemoglobins reflect the time-averaged serum glucose concentration for the preceding weeks. Canine hemoglobin also binds physiologically to intraerythrocytic glucose to form a glycated fraction which provides information on the animal's long-term glycemic status. This study describes an overall evaluation of ion-exchange microchromatography and thiobarbituric acid (TBA) colorimetry for the measurement of canine glycated hemoglobins. The intra- and inter-assay coefficients of variation (CVs) found were less than 5% in normal and diabetic canine samples, and both assays proved linear over the analytical range tested, which was wide enough to include the expected clinical values. Under our laboratory's conditions, the reference range for HbA(1) was 5.82 +/- 0.62% and for HbA(1)c was 2.35 -/+ 0.47%. Sample stability was lower using the ion-exchange procedure, with increases in HbA(1) observed after 4 days in whole blood and hemolysates stored at room temperature, after 12 days in whole blood stored at 4 degrees C, and after 7 days in hemolysates stored at 4 degrees C and -20 degrees C. In the case of TBA colorimetry, whole blood was stable for at least 21 days at room temperature and at 4 degrees C, and hemolysates were stable for 18 days at room temperature, at least 21 days at 4 degrees C, and up to 3 months at -20 degrees C.

Guidelines and Recommendations for Laboratory Analysis in the Diagnosis and Management of Diabetes Mellitus

Background: Multiple laboratory tests are used in the diagnosis and management of patients with diabetes mellitus. The quality of the scientific evidence supporting the use of these assays varies substantially.

Approach: An expert committee drafted evidence-based recommendations for the use of laboratory analysis in patients with diabetes. An external panel of experts reviewed a draft of the guidelines, which were modified in response to the reviewers’ suggestions. A revised draft was posted on the Internet and was presented at the AACC Annual Meeting in July, 2000. The recommendations were modified again in response to oral and written comments. The guidelines were reviewed by the Professional Practice Committee of the American Diabetes Association.

Content: Measurement of plasma glucose remains the sole diagnostic criterion for diabetes. Monitoring of glycemic control is performed by the patients, who measure their own plasma or blood glucose with meters, and by laboratory analysis of glycated hemoglobin. The potential roles of noninvasive glucose monitoring, genetic testing, autoantibodies, microalbumin, proinsulin, C-peptide, and other analytes are addressed.

Summary: The guidelines provide specific recommendations based on published data or derived from expert consensus. Several analytes are of minimal clinical value at the present time, and measurement of them is not recommended.

Glycohemoglobin: A Primary Predictor of the Development or Reversal of Complications of Diabetes Mellitus

Background: Diabetes mellitus is a major health problem worldwide with long-term micro- and macrovascular complications responsible for a majority of its morbidity and mortality. The development and progression of these complications relate strongly to glycemic control.

Methods: We reviewed the literature extensively for studies that relate glycemic control to the development and progression of diabetic complications. We discuss the problems of standardizing glycohemoglobin measurements for monitoring diabetic therapy and also consider recently developed electrospray ionization mass spectrometry methods that have been considered as candidate reference methods for estimation of glycohemoglobin.

Results: Several clinical trials and studies have clearly shown that improved glycemic control is strongly associated with decreased development and/or progression of complications in both type 1 and type 2 diabetes mellitus. Irrespective of the methods used for estimating glycohemoglobin, these results underline the importance of glycohemoglobin for guiding therapy of diabetes mellitus. Recently developed candidate reference methods promise to yield greatly improved standardization for the measurement of glycohemoglobin.

Conclusions: Glycohemoglobin measurement remains the optimal indicator of glycemic control in diabetic patients, but translation of findings from clinical trials to clinical practice worldwide demands consistent values across all assays. To ensure that the important prognostic information still applies to all diabetic patients with the application of the reference method(s), the hemoglobin A1c values reported in the major clinical trials will have to be translated into statistically and computationally compatible values based on the new reference system(s).

Interpretation of Hemoglobin A1c (HbA1c) Values among Diabetic Patients

Background: Few studies have examined patients’ views, knowledge, and understanding of glycohemoglobin A1c (HbA1c) testing. We explored such issues in patients with type 1 diabetes and used their statements to estimate analytical quality specifications for HbA1c testing.

Methods: We recruited 201 patients from a hospital outpatient clinic. A questionnaire was used to collect information on diabetes characteristics, perceived knowledge of HbA1c, last HbA1c value, HbA1c target value, and thresholds for action. Patients were asked to indicate the magnitude of change in HbA1c from 9.4% that they would consider to be a true (real) change; from their responses, we calculated patient-derived quality specifications for HbA1c.

Results: Fifty-eight percent of the patients felt they had “high” knowledge about HbA1c, and &gt;80% of responders knew their last HbA1c value, their target HbA1c, and the threshold value of HbA1c for treatment intensification. The mean acceptable HbA1c value was 7.5%. Patients with lower values on their most recent tests reported lower target values for HbA1c and lower values for the upper HbA1c threshold for treatment intensification. An analytical CV (CVa) of 3.1% would be satisfactory for 75% of patients when HbA1c is increasing (80% confidence), and a CVa of 3.2% would be satisfactory for 75% when HbA1c is decreasing (95% confidence).

Conclusions: Type 1 patients’ perceived knowledge about HbA1c testing is high. They are well informed about their own personal results and about target values and the upper HbA1c threshold for action. The patient-derived analytical quality specification for imprecision (CV) is 3.1%.

In Vitro Diagnostics in Diabetes: Meeting the Challenge

Diabetes is one of the leading causes of death and disability in the world. There is a large population in the world suffering from this disease, and the healthcare costs increase every year. It is a chronic disorder resulting from insulin deficiency and hyperglycemia and has a high risk of development of complications for the eyes, kidneys, peripheral nerves, heart, and blood vessels. Quick diagnosis and early prevention are critical for the control of the disease status. Traditional biosensors such as glucose meters and glycohemoglobin test kits are widely used in vitro for this purpose because they are the two major indicators directly involved in diabetes diagnosis and long-term management. The market size and huge demand for these tests make it a model disease to develop new approaches to biosensors. In this review, we briefly summarize the principles of biosensors, the current commercial devices available for glucose and glycohemoglobin measurements, and the recent work in the area of artificial receptors and the potential for the development of new devices for diabetes specifically connected with in vitro monitoring of glucose and glycohemoglobin HbA1c.

Fetal hemoglobin levels are related to metabolic control in diabetic subjects

We have investigated the relationship between fetal hemoglobin (HbF) levels and metabolic control in subjects with insulin-dependent (N = 79) and non-insulin-dependent diabetes mellitus (N = 242). HbF and hemoglobin A1c (HbA1c) levels were increased in subjects with type 1 and type 2 diabetes as compared to levels in nondiabetic individuals (P < 0.0001), and were significantly higher in type 1 than in type 2 diabetes subjects. Lower levels of HbA1c and HbF were observed in type 2 diabetes subjects treated by diet, intermediate levels in those treated with oral hypoglycemic agents, and higher levels in those treated with insulin. HbF and HbA1c levels were correlated in type 1 diabetes (R2 = 0.57, P < 0.0001) and type 2 diabetes (R2 = 0.58, P < 0.0001) subjects. Following intense treatment, twelve diabetic patients showed significant improvement both in HbA1c and HbF values. We conclude that increased HbF levels reflect poor metabolic control in subjects with diabetes mellitus.

Diagnostic utility of glycosylated hemoglobin concentrations in the cat

Changes in glycosylated hemoglobin (GHb) concentrations, K values (% disappearance of glucose/min after an intravenous injection of 1 g/kg dextrose), and blood glucose concentrations were examined in eight cats before and during the induction of diabetes, and in four of these cats after they were placed on insulin treatment. There was a statistically significant separation of GHb, K values, and fasting blood glucose concentrations between healthy and diabetic cats. Changes in GHb correlated best with the K value and single weekly fasting glucose concentrations averaged over eight periods for each cat while diabetes was induced (R = 0.80 and 0.78, respectively); however, fasting blood glucose concentrations obtained on the day of the GHb measurement were also highly correlated (R = 0.69; P < 0.001). The correlation between GHb and single weekly glucose concentrations obtained in insulin-treated cats at the time of insulin peak action and averaged over an 8-wk time period for each cat was less but still significant (R = 0.53; P < 0.001). It is concluded that GHb measurements are a simple and reliable way to monitor changes in glucose control in the diabetic cat over a prolonged period.

Direct evaluation of glycated and glyco-oxidized globins by matrix-assisted laser desorption/ionization mass spectrometry

Matrix-assisted laser desorption ionization (MALDI) mass spectrometry (MS) has been applied to achieve a qualitative and quantitative evaluation of glycated globins on a wide number of healthy and diabetic subjects. The method allowed us to establish that both alpha- and beta-globins are glycated and that, in addition to simply glycated products, other species are detected. Investigations by different sample treatments and by analysis of the glycated beta-globin fraction obtained by preparative chromatography indicated that these species correspond to glyco-oxidized globins. Consequently MALDI-MS can be validly employed to evaluate not only the glycation level, but also the degree of oxidative stress. The percentages of glycated and glycooxidized species were calculated from the related MALDI spectra by the measurement of the related peak areas, without any other treatment of data. A linear relationship between HbA1c values and the total percentage of glycated and glyco-oxidized globins has been found, and its slope (< 1) has been rationalized by the uncorrected evaluation of glycated globins content in the standard samples employed for HbA1c measurements.

Treatment of diabetes mellitus in dogs using isophane insulin penfills and the use of serum fructosamine assays to diagnose and monitor the disease

The objectives of the study were to test the use of a prefilled insulin syringe (Insulatard Novolet, isophane insulin, 100 IU/mL) in treating diabetic dogs and to test the clinical usefulness of serum fructosamine measurements in diagnosing and monitoring diabetes mellitus in dogs. For this study 15 dogs from throughout Norway with newly diagnosed diabetes mellitus were included and treated over a period of 180 days. All 15 dogs showed pretreatment hyperglycaemia. Of the 13 dogs tested, all showed elevated pretreatment serum fructosamine values. Within 2 weeks, 3 of the 15 included dogs had dropped out of the study. In 8 of the 12 remaining dogs, the clinical signs ceased within this period. Within a month, another dog was euthanised and one had died. Seven of the 10 remaining dogs were clinically normal. Three dogs had normal serum fructosamine concentrations, while in 6 dogs moderately or highly elevated serum fructosamine concentrations persisted. In one case serum fructosamine was not measured at this time. Increase in serum fructosamine concentration seemed to reflect hyperglycaemia and deteriorated clinical condition. Decrease in serum fructosamine concentration seemed to reflect improved glycaemic status and clinical condition. During the study period the owners did a total of approximately 3500 injections on their dogs. No reports of injection difficulties were received. This study documents that Insulatard Novolet is easy and safe to use in treating diabetic dogs and that serum fructosamine reflects long-term glucose concentrations in dogs. Serum fructosamine measurements provided a simple and easy way to diagnose persistent hyperglycaemia and monitor the treatment in diabetic patients.

Monitoring glycemia in diabetes. Short-term assessment

The monitoring of glycemic status is considered a cornerstone of diabetes care. This article reviews current recommendations for routine glycemia monitoring, with emphasis on practical applications. A description of the newly developed National Glycohemoglobin Standardization Program also is provided.

Ageing promotes the increase of early glycation Amadori product as assessed by epsilon-N-(2-furoylmethyl)-L-lysine (furosine) levels in rodent skin collagen. The relationship to dietary restriction and glycoxidation

Glucose has been implicated in the aging process by its ability to react nonenzymatically with long-lived proteins like collagen to produce advanced glycosylated end-products (AGEs). In the initial phase of this reaction, referred to as glycation, glucose reacts with the free amino group of proteins resulting in Schiff base formation followed by rearrangement to an Amadori product. Since the Amadori product is transient due to its conversion to other products as well as its reversibility to the initial products, glycation as an age-related marker in collagen has questionable significance. In human studies, glycation of collagen has been found to increase modestly with age. In rodent studies, results are conflicting due to differences in methodology. Thus, it has been concluded that collagen glycation either does not vary or increases modestly with age. In the present study, a C8 HPLC column was used to measure Amadori product formation as the acid-hydrolyzed breakdown product furosine in the skin of rats and mice. Surprisingly, levels were found to increase at a rapid rate during aging of rodents. Impurity of the furosine peak from the use of crude acid-hydrolyzed skin samples was ruled-out because reductive properties and spectroscopic profiles matched those previously described for furosine. In the present study, glycemia was found important in furosine formation as shown by the glycation lowering effects of dietary restriction on collagen. Decreased collagen turnover probably plays a substantial role in explaining the age-related increase in furosine levels in rodent skin collagen.

Impairment of endothelium-dependent relaxation by increasing percentages of glycosylated human hemoglobin. Possible mechanisms involved

High levels of glycosylated human hemoglobin impair nitric oxide-mediated responses. However, the percentage of glycosylation for which this effect is observed and the mechanisms involved are unknown. We tested endothelium-dependent relaxations caused by acetylcholine in rat aortic segments either in control conditions or after preincubation with increasing percentages of glycosylated human hemoglobin. Human hemoglobin (1 and 10 nmol/L) inhibited endothelium-dependent relaxations only when glycosylated at 9% or higher. We evaluated the effect of 14% glycosylated human hemoglobin on acetylcholine-evoked responses in vessels preincubated with scavengers of superoxide anions, hydroxyl radical, or hydrogen peroxide (superoxide dismutase, deferoxamine, and catalase, respectively); with inhibitors of xanthine oxidase, cyclooxygenase, or thromboxane synthase (allopurinol, indomethacin, and dazoxiben, respectively); with blockers of thromboxane A2/prostaglandin H2 or endothelin receptors (SQ 30741 and BQ-123); and with the precursor of nitric oxide synthesis L-arginine. Superoxide dismutase abolished the effect of glycosylated hemoglobin, and the other substances did not have any effect. Glycosylated hemoglobin at 14% did not modify either the vasoconstrictions induced by the blocker of nitric oxide synthase NG-nitro-L-arginine methyl ester or the relaxations evoked in deendothelialized vessels by sodium nitroprusside and 8-bromo-cGMP. However, it inhibited the vasodilations evoked by exogenous nitric oxide. Superoxide dismutase abolished this latter effect. We conclude that the threshold for glycosylated human hemoglobin (Hb A1) to inhibit endothelium-dependent relaxation is 9%. This effect is due to interference with endothelial nitric oxide by means of superoxide anion production.

Predictors of stroke in middle-aged patients with non-insulin-dependent diabetes

BACKGROUND AND PURPOSE

The risk of stroke is known to be markedly elevated in patients with non-insulin-dependent diabetes mellitus (NIDDM), but the information on risk factors predicting stroke events in middle-aged NIDDM patients is limited. Therefore, we evaluated the significance of different cardiovascular risk factors with respect to the incidence of stroke in middle-aged NIDDM patients.

METHODS

Levels of cardiovascular risk factors were determined at baseline in 1059 NIDDM patients (581 men, 478 women) and 1373 nondiabetic control subjects (638 men, 735 women), aged from 45 to 64 years, in eastern and western Finland. These patients were followed up for 7 years with respect to stroke events.

RESULTS

Altogether, 34 NIDDM patients (13 men, 21 women) and 5 nondiabetic subjects (4 men, 1 woman) died from stroke, and 125 NIDDM patients (61 men, 64 women) and 30 (18 men, 12 women) nondiabetic subjects had a fatal or nonfatal stroke. The risk of stroke in NIDDM men was about threefold and in NIDDM women fivefold higher than that in corresponding nondiabetic subjects. Previous history of stroke increased the risk of a new stroke event by threefold. Patients with hyperglycemia (plasma glucose > 13.4 mmol/L) and high hemoglobin A1 (> 10.7%) had about a twofold higher risk of stroke than patients with better glycemic control. Low levels of high-density lipoprotein cholesterol (< 0.90 mmol/L), high levels of total triglyceride (> 2.30 mmol/L), and the presence of hypertension were associated with a twofold increase in the risk of stroke mortality or morbidity.

CONCLUSIONS

Our prospective population-based study gives evidence that previous history of stroke, hypertension, hyperglycemia, and dyslipidemia are strong predictors of stroke in middle-aged patients with NIDDM.

Effects of age and obesity on glycated haemoglobin and 1,5-anhydroglucitol in screening for type 2 diabetes mellitus

The diagnostic accuracy of glycated haemoglobin (HbA1c) and 1,5-anhydroglucitol (AG) and their association with age and obesity in the community screening for Type 2 diabetes were investigated. HbA1c and AG were measured in 368 subjects at the time of an oral glucose tolerance test (OGTT) based on WHO criteria. The impact of age and obesity on the probability of diabetes was evaluated by multivariate logistic regression analysis. Receiver operating characteristic (ROC) analysis was used to assess diagnostic accuracy of each method. The areas under ROC curves were compared for subjects aged 30-59 and 60-82 years. In the logistic analysis, age was associated with the probability of diabetes, while body mass index did not contribute to the model. The paired ROC analyses indicated that HbA1c was superior to AG only in the younger subjects. When the areas for two age groups were compared, both HbA1c and AG performed better in the younger than older subjects. We conclude that for the younger subjects, HbA1c value is highly sensitive (100.0%) and specific (90.4%) and is helpful for the diagnosis of Type 2 diabetes. On the other hand for the older subjects, both HbA1c and AG are poor screening tests in reference to the OGTT standard.

Non-insulin-dependent diabetes and its metabolic control are important predictors of stroke in elderly subjects

BACKGROUND AND PURPOSE

Non-insulin-dependent diabetes mellitus (NIDDM) is a major risk factor for stroke in the middle-aged population, but few prospective population-based studies are available in the elderly. Moreover, the importance of metabolic control and the duration of diabetes in diabetic subjects has remained controversial. There are no previous studies on association of insulin with the risk of stroke. The present study examined whether NIDDM, its metabolic control and duration, and insulin level predict stroke.

METHODS

We measured cardiovascular risk factors including glucose tolerance, plasma insulin, and glycosylated hemoglobin A1c in a Finnish cohort of 1298 subjects aged 65 to 74 years and investigated the impact of these risk factors on the incidence of both fatal and nonfatal stroke during 3.5 years of follow-up.

RESULTS

Of 1298 subjects participating in the baseline study, 1069 did not have diabetes and 229 had NIDDM. During the 3.5-year follow-up, 3.4% (n = 36) of nondiabetic subjects and 6.1% (n = 14) of NIDDM subjects had a nonfatal or fatal stroke. The incidence of stroke was significantly higher in diabetic women compared with nondiabetic women (odds ratio [OR], 2.25; 95% confidence interval [CI], 1.65 to 3.06). In contrast, the risk of stroke was not significantly higher in diabetic men than in nondiabetic men (OR, 1.36; 95% CI, 0.44 to 4.18). In multivariate logistic regression analyses including all study subjects, fasting and 2-hour glucose (P < .01 and P < .05, respectively), glycosylated hemoglobin A1c (P < .01), atrial fibrillation (P < .05), hypertension (P < .05), and previous stroke (P < .01) predicted stroke events. In diabetic subjects, fasting and 2-hour glucose (P < .01 and P < .05, respectively), glycosylated hemoglobin A1c (P < .05), the duration of diabetes (P < .05), and atrial fibrillation (P < .05) were the baseline variables predicting stroke events. Finally, fasting insulin (P < .05), hypertension (P < .05), and previous stroke (P < .01) were associated with stroke incidence in nondiabetic subjects.

CONCLUSIONS

Our 3.5-year follow-up study provides evidence that NIDDM, its metabolic control, and the duration of diabetes are important predictors of stroke in elderly subjects, particularly in women. Moreover, fasting insulin level appears to be a risk factor for stroke in elderly nondiabetic subjects.

The relationship of blood glucose and haemoglobin A1 levels in diabetic subjects

Recommendations exist that fasting plasma glucose (FPG) levels can be substituted for glycosylated haemoglobin A1 (HbA1) in Type II diabetic subjects (DM II), which have potential important financial implications. The present study was designed to expand this examination and to include Type I DM (DMI) patients and random blood glucose (RBG) values. Data were obtained from 234 DM II and 104 DM I patients, over 3 years. Correlation of HbA1 with FPG levels in DM II yielded an r value of 0.61. Correlation of HbA1 with RBG and 2 h post prandial glucose measurements yielded r values of 0.59 and 0.51 respectively, p < 0.001. In DM I, similar correlations gave r values ranging between 0.27 and 0.38, p < 0.01-0.001. Thus while significant correlations exist between HbA1 and FPG and RBG measurements in both DM I and DM II, clinically applicable information on long-term diabetic control can only be achieved from glucose measurements in DM II but the correlation is not sufficiently tight to recommend substitution of plasma glucose for HbA1 determinations, despite the cost advantages.

Glycated haemoglobin predicts progression to diabetes mellitus in Pima Indians with impaired glucose tolerance

Glycated haemoglobin could offer several practical advantages over the OGTT for assessing glucose metabolism. Initial cross-sectional studies (1983-1985) on 381 subjects (mostly Pima Indians) described the relationship between HbA1c (a specific glycated Hb) and the OGTT. We performed follow-up OGTTs and HbA1c measurements on 257 of these same subjects 1.6-6.1 years later. Subjects were again grouped according to both the result of the OGTT (normal, IGT or diabetes, by WHO criteria) and HbA1c result (normal or elevated based on mean +/- 1.96 SD of normal). Of 66 subjects with IGT at baseline, 47 (71%) had normal HbA1c and 19 (29%) had elevated HbA1c. Twenty-six (39%) of these subjects had diabetes at follow-up. Of these subjects with IGT, a significantly greater percentage of subjects with elevated HbA1c at baseline (68%) showed worsening to diabetes than those with a normal HbA1c (28%); (chi-square = 7.8, df = 1, p < 0.01). Thus, in subjects with IGT, glycated Hb may be a useful predictor of progression to diabetes.

Interference of glycosylated human hemoglobin with endothelium-dependent responses

BACKGROUND

Hypertension and other vascular diseases are more prevalent in diabetic patients than in the general population. In humans and in several animal models of diabetes, a disturbance of endothelium-dependent responses has been shown. Oxyhemoglobin is one of the most known modulators of these endothelium-dependent responses. We postulate that high levels of plasmatic glycosylated hemoglobin, a frequent profile in diabetic patients, may be the cause of the disturbance in endothelium-dependent relaxation and/or contraction.

METHODS AND RESULTS

Endothelium-dependent responses to acetylcholine and several alpha-adrenergic agonists (norepinephrine, methoxamine, and clonidine) were tested in segments of rat aorta. Experiments were carried out in control segments and in those preincubated with several concentrations of nonglycosylated, low-glycosylated (7.3%), and high-glycosylated (14%) human hemoglobin. Low concentrations of high-glycosylated human hemoglobin (1 to 100 nmol/L) but not of low- or nonglycosylated hemoglobin, inhibited endothelium-dependent relaxation caused by acetylcholine in intact vessels. The same effect was observed on relaxations caused by nitric oxide in denuded ones. High-glycosylated human hemoglobin (10 nmol/L) induced an increase in norepinephrine-evoked contraction in intact vessels; this latter effect was also shown in vessels contracted with methoxamine but not with clonidine. De-endothelialization of the vascular segments blunted these effects of high-glycosylated human hemoglobin.

CONCLUSIONS

High glycosylation of human hemoglobin impairs endothelium-mediated vasoactive responses and may play a pathophysiological role in producing hypertension and vascular diseases in diabetic patients.

Reliability and validity of the Diabetes Family Behavior Scale (DFBS)

The Diabetes Family Behavior Scale (DFBS) was designed to measure diabetes-specific family support. The purposes of this study were to refine the scale and to assess reliability and criterion validity in terms of relationship to metabolic control. The DFBS was administered to 321 children and adolescents with insulin-dependent diabetes mellitus (IDDM). Blood was drawn for determination of glycosylated hemoglobin (HbA1c). Based on an item-analysis procedure, the DFBS was revised to include 47 items with two subscales, one to reflect guidance-control and one to reflect warmth-caring. Acceptable internal consistency was found for the DFBS total score (.86), and for the guidance-control (.81) and warmth-caring (.79) subscales. There was a statistically significant relationship in the expected direction between DFBS total score and HbA1c (r = -.12, P < .03), and between the guidance-control subscale and HbA1c (r = -.17, P < .002).

The reappraisal of the association of glycosylated hemoglobin A1c (HbA1c) and blood pressure: a hypertension and diabetes study in a Taiwan rural area

The association of age, body weight, body mass index (BMI) and glycosylated hemoglobin A1c (HbA1c) to blood pressure in the general population of the Ho-long area in Taiwan was examined. A total of 1341 subjects, 746 men and 595 women, aged 40-90 years, were studied. Sex-specific multiple regression analyses were carried out on variables both univariately and significantly associated with blood pressure. Results show HbA1c to be significantly associated with SBP in both males and females before age, weight and/or BMI are adjusted (p < 0.05). After controlling for these confounders, the strength of SBP-HbA1c association was slightly reduced in males, but remained significant. In contrast, there was no significance in females. Moreover, no significant relationship in DBP-HbA1c was found in either sex group. These findings suggest that although a positive correlation was found between HbA1c and SBP, HbA1c or glucose status appeared to be a less important contributing factor in hypertension than age or body weight.