The clinical value of glycated haemoglobin and glycated plasma proteins

AGEs-Induced and Endoplasmic Reticulum Stress/Inflammation-Mediated Regulation of GLUT4 Expression and Atherogenesis in Diabetes Mellitus

In recent decades, complex and exquisite pathways involved in the endoplasmic reticulum (ER) and inflammatory stress responses have been demonstrated to participate in the development and progression of numerous diseases, among them diabetes mellitus (DM). In those pathways, several players participate in both, reflecting a complicated interplay between ER and inflammatory stress. In DM, ER and inflammatory stress are involved in both the pathogenesis of the loss of glycemic control and the development of degenerative complications. Furthermore, hyperglycemia increases the generation of advanced glycation end products (AGEs), which in turn refeed ER and inflammatory stress, contributing to worsening glycemic homeostasis and to accelerating the development of DM complications. In this review, we present the current knowledge regarding AGEs-induced and ER/inflammation-mediated regulation of the expression of GLUT4 (solute carrier family 2, facilitated glucose transporter member 4), as a marker of glycemic homeostasis and of cardiovascular disease (CVD) development/progression, as a leading cause of morbidity and mortality in DM.

Is the measurement of glycated hemoglobin A1c alone an efficient screening test for undiagnosed diabetes? Japan National Diabetes Survey

The aim of the study was to assess the screening test properties of HbA1c for undiagnosed diabetes (DM) according to the 1999-WHO criteria and its relevance of the Japan National Diabetes Survey Cut-off points for possible and probable DM: HbA1c >or=5.6 and 6.1%. Screening properties of HbA1c predicting undiagnosed DM was examined and compared with that of fasting plasma glucose (FPG) in 1904 Funagata-town inhabitants aged 35-89 years old. The prevalence of previous DM, undiagnosed DM, and impaired glucose regulation (IGR) were 5.5, 6.0, and 18.6%, while the prevalence of probable and possible DM were 7.7 and 5.4%. The area under the receiver operating characteristic curve for undiagnosed DM was similar between HbA1c (0.856 [95% CI: 0.812-0.899]) and FPG (0.902 [0.869-0.936]). HbA1c of 5.6% gave a sensitivity of 56.5%, a specificity of 95.1%, positive and negative predictive values of 44.2 and 97.0%, and a proportion of people above the cut-off point of 8.2%. True positive tests were significantly higher with mean levels of BMI, fasting, and 2-h plasma glucose, and HbA1c, but lower with mean levels of high-density-lipoprotein cholesterol than in false negative tests. The measurement of HbA1c alone may be efficient to screen undiagnosed DM and the cut-off point of 5.6% might be proper with respect to screening tests properties for undiagnosed DM, and prediction of vascular complications in Japan.

Plasma Prekallikrein as a Risk Factor for Diabetic Retinopathy

BACKGROUND

The aim of the study was to verify the hypothesis that in diabetes there is an increased activation of coagulation system leading in consequence to diabetic retinopathy.

METHODS

Thirty three healthy subjects (controls, 16 males and 17 females) and 35 patients with diabetes type 1 (15 males and 20 females) were examined. We monitored plasma prekallikrein (PPK), glycemia, fructosamine, glycosylated hemoglobin, activated partial thromboplastin time (PTT), INR, fibrinolysis in euglobulins time (FET), level of antithrombin III (AT III), fibrinogen (Fb) and fibrinogen degradation products (FDP).

RESULTS

In diabetic patients without retinopathy, PKK concentration was 16% higher (p <0.005), in patients with background retinopathy 33% higher (p <0.001), and in patients with proliferative retinopathy PKK concentration was 50% higher (p <0.001) than in controls. In the subgroup of patients with proliferative retinopathy PTT was significantly shorter (p <0.001), and FET was significantly longer (p <0.001) than in control. In patients with diabetes higher FDP concentrations were found than in controls (p <0.05). Significant correlations were found between PPK and fructosamine levels in all diabetic patients (R(S)=+0.57 p <0.001), in diabetic patients without retinopathy (R(S)=+0.61, p <0.05), and in diabetic patients with retinopathy (R(S)=+0.62, p <0.005). We found negative correlation between PPK concentration and PTT (R(S)=-0.43, p <0.001) and positive correlation between PPK concentration and FET (R(S)=+0.59, p <0.00001) in the entire study group.

CONCLUSIONS

The occurrence of diabetic retinopathy is connected with higher levels of plasma prekallikrein.

Serum concentrations of IGF-I, IGFBP-3 and c-peptide and risk of hyperplasia and cancer of the breast in postmenopausal women

Experimental evidence suggests that insulin and insulin-related growth factors may play a role in breast pathology through their mitogenic and anti-apoptotic effects on breast cells. Our objective was to assess the relationship between serum concentrations of insulin-like growth factor-I (IGF-I), its major binding protein (IGFBP-3), the ratio IGF-I:IGFBP-3, c-peptide (a marker of insulin secretion) and the ratio c-peptide:fructosamine (a marker of insulin resistance) and the risk of epithelial hyperplasia (an established breast cancer risk factor) and localized breast cancer among postmenopausal women. Study subjects were patients who provided serum before breast biopsy or mastectomy in 3 hospitals in Grand Rapids, MI between 1977 and 1987. Two case groups, 186 subjects with epithelial hyperplasia of the breast and 185 subjects with localized breast cancer, were compared to 159 subjects with nonproliferative breast changes that have not been associated with increased breast cancer risk. Serum concentrations of IGF-I, IGFBP-3 and the ratio IGF-I:IGFBP-3 were not related to risk of either hyperplasia or breast cancer. For women in the highest quartile of c-peptide or of c-peptide:fructosamine compared to those in the lowest quartile, the odds ratios (ORs) for hyperplasia were 3.0 (95% confidence interval [CI] 1.4-6.5) and 3.3 (95% CI 1.5-7.3), respectively (p trend = 0.02 and 0.02, respectively). The corresponding ORs for breast cancer were 1.5 (95% CI 0.7-3.0) and 1.6 (95% CI 0.8-3.2), respectively (p trend = 0.35 and 0.25, respectively). Our results suggest that insulin and insulin resistance may play a role in breast pathology in postmenopausal women.

Clinical validity of a self-test fructosamine in outpatient diabetic management

BACKGROUND

Measurement of glycated hemoglobin and hemoglobin A1c (HbA1c) is now well established as the best means of measuring overall glucose control in managing diabetes. Other glycated serum protein assays reflecting recent glycemic control, e.g., glycated albumin and glycated protein (fructosamine), have also been validated in clinical studies. Regardless of the method, the expense and inconvenience of laboratory testing of blood samples may contribute to the well-documented underutilization of clinical glycated protein assessment. Accordingly, a rapid, inexpensive fingerstick test of fructosamine has been developed. This study cross-sectionally and prospectively assesses the clinical validity of fingerstick fructosamine versus laboratory determination.

METHODS

Fifty-one subjects (18 control, 33 with diabetes) participated in a cross-sectional study and 20 subjects with type 2 diabetes participated in a prospective, 6-week study with clinical intervention consisting of glipizide gits or metformin in mono- and combination therapy. Subjects had weekly laboratory determination of serum fructosamine, glycated hemoglobin, and fasting glucose; fingerstick fructosamine was obtained at each clinic visit.

RESULTS

Fingerstick fructosamine was shown to correlate highly to laboratory fructosamine (r = 0.80, p < 0.001) and glycated hemoglobin (r = 0.81, p < 0.001). In the clinical intervention study subjects, significant decreases in fasting glucose (p < 0.001), laboratory fructosamine (p < 0.001), and fingerstick fructosamine (p < 0.001) were noted compared to baseline. The subject's self-test fingerstick fructosamine mirrored laboratory testing of fructosamine in detection of changes in clinical glucose control.

CONCLUSIONS

This study demonstrates that fingerstick fructosamine correlates well to laboratory assessment of fructosamine and glycated hemoglobin. The patient self-test fructosamine provides the same clinical information as laboratory assessment.

Clinical value of glycated hemoglobin and fructosamine in the long-term glycemic control of children with acute lymphoblastic leukemia

Hyperglycemia in children with acute lymphoblastic leukemia (ALL) has been well documented in the literature. The purpose of the present study was to evaluate the clinical value of glycated hemoglobin (GHb) and fructosamine (Frc) in the long-term glycemic control of ALL patients. An attempt was made to identify the risk factors for hyperglycemia in ALL patients. The study group comprised 26 newly diagnosed ALL patients admitted to hospital during 1995-96. Patients with a history of blood transfusion or infection within the past 3 months were excluded from the study. White blood cell (WBC) counts, fasting blood glucose (FBG), GHb and Frc levels were analyzed in venous blood on screening day 0, before induction of chemotherapy. Frc analysis was repeated on the 21st day and GHb level on the 60th day of chemotherapy. FBG tests were performed before each dose of L-asparaginase, on days 21 and 60. None of the patients was obese. Although six children (23%) had hyperglycemia during the induction therapy, four of them had a GHb level higher than normal on admission. Only one patient who developed hyperglycemia had a family history of diabetes mellitus. Patients with a high initial WBC count (> 20 x 10(9)/L) had a significantly higher baseline GHb than patients with a WBC count below this level. GHb values returned to normal after achievement of complete remission. It is suggested that the leukemic process could impair glucose metabolism and baseline GHb may be used to monitor possible small changes in glucose homeostasis of ALL patients, prior to chemotherapy.

The reproducibility and usefulness of the oral glucose tolerance test in screening for diabetes and other cardiovascular risk factors

We examined the reproducibility of oral glucose tolerance tests (OGTT) using the World Health Organization criterion in 212 Chinese subjects (male 149, female 63) who underwent two 75 g OGTTs within a 6-week period. The overall reproducibility was 65.6% (139/212) of which 74 subjects had normal glucose tolerance, 24 had diabetes and 41 had impaired glucose tolerance (IGT) on two occasions. The subjects were divided into three groups [group 1: normal OGTTs on both occasions (n = 74); group 2: one abnormal OGTT (either diabetes or IGT (n = 51); group 3: 2 abnormal OGTTs (n = 87)]. Subjects in group 1 were younger, had lower blood pressure, body mass index (BMI), waist-to-hip ratio (WHR), fasting and 2 h plasma insulin levels, triglyceride, very-low density lipoprotein and apolipoprotein-B concentrations than both groups 2 and 3. Group 2 had similar characteristics as group 3 except for a lower glycated haemoglobin (HbA1c), fasting and 2 h plasma glucose during the two OGTTs. With receiver operating characteristic curve (ROC) analysis, a HbA1c of 5.3% gave an optimal sensitivity of 70.7% and specificity of 74.3% to predict diabetes as defined by a 2 h plasma glucose value > or = 11.1 mmol/L in the first OGTT. Of the 212 subjects, 73 had HbA1c > or = 5.3%. The reproducibility of OGTT was 56.2% for these 73 subjects. With ROC analysis, a BMI of 25 kg/m2 gave an optimal sensitivity of 53.7% and specificity of 56.7% to predict diabetes. For the 36 subjects with BMI > or = 25 kg/m2, the reproducibility of OGTT was 58.3%. Similarly, for the 140 subjects with WHR > or = 0.9, the reproducibility of OGTT was 57.9%. These findings confirmed the poor reproducibility of OGTT which was not improved even amongst subjects with high HbA1c, BMI or WHR. Furthermore, subjects with one abnormal OGTT, whether reproducible or not, had a higher cardiovascular risk profile compared to subjects who had two normal OGTTs.

Chromatographic and electrophoretic methods for modified hemoglobins

The discovery of the clinically important glycohemoglobin adducts and their relation to diabetes mellitus have greatly stimulated the study of other minor post-translational modifications of hemoglobin. Chromatographic and electrophoretic procedures have played an important role in these studies. Today several hemoglobin adducts are known and the formation of adducts with glucose, phosphorylated carbohydrates, urea/cyanate, aspirin, vitamins, acetaldehyde, penicillin and acetyl CoA have been described. Furthermore, new adducts, such as those observed using hemoglobin as a biochemical marker monitoring environmental, occupational and lifestyle exposures to reactive toxic chemicals are constantly being reported. This review deals with chromatographic and electrophoretic separation methods available for the study of non-enzymatic post-translational modifications of hemoglobin. Suitability, perspectives and biomedical applications are discussed.

The effect of delta-gluconolactone, an oxidised analogue of glucose, on the nonenzymatic glycation of human and rat haemoglobin

Nonenzymatic glycation of proteins and oxidative stress are considered independent factors important in the development of the complications of diabetes but may be interrelated by the process of autoxidative glycation. This pathway involves monosaccharide autoxidation to a reactive ketoaldehyde analogue and subsequent reaction with protein to form a ketoimine adduct. This study demonstrates that delta-gluconolactone (delta-GL), an oxidised analogue of glucose, is a potent glycating agent in vitro of haemoglobin present in blood samples from insulin-dependent diabetic and non-diabetic human subjects and from spontaneously diabetic, insulin-dependent BB/Edinburgh (BB/E) rats. The percentage glycated haemoglobin after incubation (37 degrees C, 5 h) with delta-GL (25 mmol/l) was significantly (P < 0.002) higher than that observed using an equimolar concentration of glucose. Intravenous administration of delta-GL (1 g/kg) to non-diabetic BB/E rats also significantly increased glycation of haemoglobin (6.0 +/- 0.1% vs 4.9 +/- 0.1%, P < 0.01) whereas intravenous injection of an identical dose of glucose had no significant effect (5.1 +/- 0.1% vs 5.0 +/- 0.2%). These results support the hypothesis that nonenzymatic glycation of proteins involves attachment by both native and oxidised monosaccharides. Further investigation of the interactions between diabetes-associated increases in oxidative stress and glycation on the development and progression of the vascular complications of diabetes is necessary.

Comparison of antioxidant activity in lipoprotein fractions from insulin-dependent diabetics and healthy controls

The insulin-dependent diabetic patient is at greatly increased risk of premature atherosclerosis. Oxidative damage to lipoproteins has been implicated as an important factor in the atherogenic process. Diabetic patients are exposed to excessive oxidative stress because of non-enzymatic glycation of proteins and a variety of defects in antioxidant systems. We have previously described an enhanced chemiluminescent method for measuring protective 'chain-breaking' antioxidant activity in plasma lipoprotein fractions. In this study we compare the lipid content and antioxidant activity of plasma lipoproteins in 22 young insulin-dependent diabetics without vascular complications and 20 age- and sex-matched controls. Mean levels of haemoglobin A 1c in the diabetic group were 8.8 +/- 0.2%. There were no significant differences in serum total cholesterol, apolipoprotein A, apolipoprotein B or lipoprotein(a) levels between the study groups. Serum total triglyceride levels (1.32 +/- 0.11 versus 1.01 +/- 0.08 mmol/l; P < 0.05) and LDL-associated triglyceride (0.28 +/- 0.04 versus 0.15 +/- 0.02 mmol/l; P < 0.05) were significantly elevated in the diabetic group. Total plasma antioxidant activity was significantly reduced in the diabetic group (272.0 +/- 15.4 versus 338.3 +/- 20.7 micromol/l; P < 0.05). Antioxidant activity measured in five lipoprotein fractions isolated by density gradient ultracentrifugation (VLDL1. VLDL2, LDL1, LDL2 and HDL) showed no significant differences between groups when corrected for protein, total lipid or cholesterol content. When corrected for triglyceride content significantly lower antioxidant values were found in the diabetic HDL fraction only. The results of this study imply that the susceptibility of the insulin-dependent diabetic to the development of premature atherosclerosis cannot be attributed to reduced antioxidant activity in circulating plasma lipoproteins.

Plasma ubiquinol/cholesterol ratios in patients with hyperlipidaemia, those with diabetes mellitus and in patients requiring dialysis

Plasma ubiquinol was measured in diabetics, patients on haemodialysis (HD) therapy, patients maintained by continuous ambulatory peritoneal dialysis (CAPD), hyperlipidaemic patients and control subjects. Ubiquinol values were standardized using total cholesterol (mumol/mmol). Diabetics, HD and CAPD patients were found to have plasma ubiquinol levels which were lower than the control subjects. There was no difference in values between the control subjects and hyperlipidaemic patients. Values for diabetics with poor metabolic control were similar to those with good control, and patients with diabetic complications had values which were not significantly different from those for patients with no complications. IDDM patients were found to have values which were lower than the control group, whereas values for the NIDDM patients were not significantly different. These results suggest that increased oxidative stress in certain patient groups may be the result of, and/or the cause of, decreased plasma ubiquinol. This could be due to increased demand or to decreased ability to regenerate the effective form of antioxidant.

Glycated haemoglobin and metabolic control of diabetes mellitus: external versus locally established clinical targets for primary care

OBJECTIVES

To examine current targets for glycated haemoglobin as a marker for metabolic control in diabetes mellitus in relation to datasets from several areas, and to consider whether target setting could be improved.

DESIGN

Data collected from enhanced care records of general practices for a representative community based sample of people with diabetes.

SETTING AND SUBJECTS

3022 people with diabetes on the lists of 37 general practices (total list size 222,550) in South Glamorgan in 1992; samples of glycated haemoglobin had been processed at two laboratories with different methodologies and reference ranges.

MAIN OUTCOME MEASURES

Last glycated haemoglobin level measured in subjects for 1992 and published data from other studies considered in relation to existing goals and standards for the metabolic control of diabetes.

RESULTS

An ascertainment rate for people with diabetes of 1.36% was obtained. The rate of data capture for haemoglobin A1 was 75.7%, and the mean level for study samples was 10.5% at one laboratory and 10.0% at the other (similar values to those of comparable studies). These mean levels of haemoglobin A1 in representative populations of people with diabetes are poor or very poor according to published standards, including those of the British Diabetic Association. These findings are set in the context of the psychology of goal setting and performance in complex clinical situations.

CONCLUSION

Targets for clinical care that are set in the absence of normative data and local feasibility assessments should be treated with caution. Targets are more likely to enhance health care if target setters recognise the importance of psychological aspects of goal setting and motivation.

Serum immunoglobulin concentrations in diabetic patients

The relationship between glycated haemoglobin (an index of long-term diabetic control), fructosamine (an index of intermediate-term diabetic control), and serum IgA, IgG, and IgM was studied in 110 diabetic patients (41 Type 1 and 69 Type 2) and compared with 111 healthy non-diabetic subjects. Significant increases in serum IgA (by 82.7%, p < 0.001) and IgG (by 35.2%, p < 0.001) concentrations were observed whereas the concentration of IgM was significantly decreased (by 46.7%, p < 0.001) in diabetic patients compared with non-diabetic subjects. Using Spearman's rank correlations, IgA correlated with fructosamine (r = 0.77, p < 0.001), HbA1 (r = 0.76, p < 0.001), and albumin (r = -0.58, p < 0.001) for the entire population sample but only fructosamine (r = 0.19, p < 0.05) and HbA1 (r = 0.28, p < 0.001) correlated with IgA in diabetic patients, respectively. It is concluded that abnormal levels of IgA, IgG, and IgM are very common in diabetic patients in whom serum IgA concentrations are influenced by the degree of glycaemic control. Whether changes in IgA and other immunoglobulins are implicated in the pathogenesis of diabetic complications (such as susceptibility to infection) deserve further study.

Fructosamine in obese normal subjects and type 2 diabetes

The effect of various grades of obesity on serum fructosamine concentrations was studied in Type 2 diabetic (n = 105) and non-diabetic (n = 128) subjects. In obese diabetic and non-diabetic subjects (body mass index > or = 30 kg m-2), the concentration of fructosamine was markedly lower than that obtained for lean diabetic and non-diabetic subjects with similar glycaemic control. Stepwise multiple-regression analysis showed that fructosamine was associated with glycaemic control (as indicated by fasting plasma glucose and glycated haemoglobin), fasting triglycerides, and body mass index in both diabetic and non-diabetic subjects. In vitro studies showed marked decreases in both the extent of [14C]-glucose incorporation into plasma proteins and fructosamine production by incubated sera of obese patients whether diabetic or non-diabetic, with obese subjects with body mass index > 40 kg m-2 exhibiting the greatest decrease. In conclusion, serum fructosamine concentrations are shown to decrease in obese diabetic and non-diabetic subjects with body mass index > or = 30 kg m-2 giving rise to the underestimation of glycaemic control as indicated by fructosamine measurement. A change in the glycation reaction itself may be partly responsible for such decrease.

Serum fructosamine as a screening test for diabetes in the elderly: a pilot study

OBJECTIVE

To determine the value of serum glycated protein, measured as serum fructosamine, as a screening test for diabetes in the elderly.

DESIGN

Cross-sectional pilot study.

SETTING

Ambulatory research clinic in university setting.

PATIENTS

One hundred fifty-seven consecutive community-dwelling participants in the Cardiovascular Health Study, average age 71.8 + 5 (mean +/- SD, range 65-88 years).

MEASUREMENTS

Serum fructosamine levels (first and second generation assay) were obtained. All subjects who did not have a diagnosis of diabetes were given a 75-g glucose tolerance test (GTT).

RESULTS

Twenty-six subjects (17%) (10 previously diagnosed, 16 undiagnosed and asymptomatic) had diabetes mellitus, and 38 subjects (24%) had impaired glucose tolerance by history or by the GTT (WHO criteria). Only the 16 asymptomatic diabetics were included in the analysis for the pilot study. There was a significant difference in the fasting fructosamine level between non-diabetics and asymptomatic diabetics for the first generation (2.06 +/- .21 vs 2.53 +/- .49 mMol/L, P < 0.0015) and second generation assay (221 +/- 27 vs 269 +/- 48 mMol/L, P < 0.0012). Receiver operator curves were constructed to evaluate the test characteristics of serum fructosamine. Using a point of > or = 2.3 mMol/L for the first-generation assay, the sensitivity to detect asymptomatic diabetes was 75%, specificity 83%, and positive predictive value 35%. To detect both diabetes and impaired glucose tolerance using a cutpoint of > or = 2.3 mMol/L, the sensitivity was 24%, specificity 95%, and positive predictive value 68%. Employing a cut point of 250 muMol/L for the second generation assay, the sensitivity to detect diabetes was 81%, specificity 87%, and positive predictive value 43%. However, to detect diabetes and glucose intolerance using the second generation assay, the sensitivity was 39% and specificity was 86%.

CONCLUSION

This study demonstrated that a single measurement of either first or second generation fructosamine showed promise as a screening test for diabetes, but not impaired glucose tolerance, in older people.

Glycosylated serum proteins and glycosylated hemoglobin in the assessment of glycemic control in insulin-dependent and non-insulin-dependent diabetes mellitus

To evaluate the relative value of glycosylated serum proteins (GSPs) versus glycosylated hemoglobin (HbA1c) in assessing glycemic control in diabetes mellitus, we performed regular monitoring of GSPs and HbA1c in 30 subjects with insulin-dependent diabetes mellitus (IDDM) or non-insulin-dependent diabetes mellitus (NIDDM) who performed frequent self-glucose monitoring. Analysis of the relationship between patterns of glycemic control and GSPs and HbA1c demonstrated that subjects with IDDM and NIDDM appeared similar when the more traditional indicators of glycemic control such as mean blood glucose level (166.9 +/- 20.9 v 177.4 +/- 39.6 mg/dL) or HbA1c (83.57 +/- 12.8 v 80.24 +/- 15.7 mmol hydroxymethyl furfuraldehyde [HMF]/mol hemoglobin [Hgb]) were used. However, when GSP levels or the standard deviation of mean glucose levels (SDMG) were used to assess glycemic control, higher levels were found in subjects with IDDM (52 +/- 10.3 mg/g protein and 28.59 +/- 7.60 mg/dL) versus NIDDM (44.6 +/- 15.2 mg/g protein and 21.6 +/- 15.9 mg/dL). Using multivariate analysis, GSPs were predictive of SDMG (P = .046), whereas HbA1c added no significant further information (P = .27). Our results suggest that GSPs may be more sensitive than HbA1c assay to the greater fluctuations in blood glucose levels generally associated with IDDM.

Glycated haemoglobin centiles: a basis for audit in children's clinics?

Services for children with diabetes are a good model for audit because of relatively well-defined and available measures of outcome. Estimation of glycated haemoglobin (HbA1) is accepted as one index of control, although the assay and normal ranges vary in different centres. Sheffield has a stable clinic population and we have taken blood for HbA1 on each patient two to four times per year since 1983. HbA1 values have been aligned in 3-monthly increments from time of diagnosis to construct a graph showing the mean plus or minus two standard deviation values for the clinic population and also a rough 'centile chart' that describes the unfortunate but expected pattern of deteriorating control with duration of diabetes. There are undoubtedly methodological flaws in this novel approach; however, such charts constructed for each clinic may be a suitable basis for comparative assessment of the control of an individual and also for auditing the effects of changes in practice that strive for optimum glucose levels in the clinic population.

Insulin resistance and breast-cancer risk

Life-style has a major influence on the incidence of breast cancer. To evaluate the effects of life-style related metabolic-endocrine factors on breast cancer risk we conducted a case-control study comparing 223 women aged 38 to 75 years presenting with operable (stage I or II) breast cancer and 441 women of the same age having no breast cancer, who participated in a population-based breast cancer screening program. Women reporting diabetes mellitus were excluded. Sera from 110 women of the same age group presenting with early stage melanoma, lymphoma or cervical cancer were used as a second 'other-cancer control group'. Serum levels of C-peptide were significantly higher in early breast cancer cases compared to controls. The same was found for the ratios C-peptide to glucose or C-peptide to fructosamine, indicating insulin resistance. Sex hormone binding globulin was inversely, triglycerides and available estradiol were positively related to C-peptide. Serum C-peptide levels were related to body mass index (BMI), and to waist/hip ratio (WHR), in particular in controls. However, the relative increase of C-peptide, C-peptide to glucose or C-peptide to fructosamine in cases was independent of BMI or WHR. The log relative risk was linearly related to the log C-peptide levels. Relative risk according to quintiles, and adjusted for age, family history, BMI and WHR, for women at the 80% level was 2.9 as compared with those at the 20% level for C-peptide. Elevated C-peptide or C-peptide to fructosamine values were not observed in the sera from women belonging to the 'other-cancer control group'. This study suggests that hyperinsulinemia with insulin resistance is a significant risk factor for breast cancer independent of general adiposity or body fat distribution.

The inter-relationships between albuminuria, plasma albumin concentration and indices of glycaemic control in non-insulin-dependent diabetes mellitus

We studied the relationship between albuminuria (measured as albumin/creatinine ratio (alb/Cr) in a random urine sample) and measures of glycaemic control (fructosamine, HbA1 and glucose) in 470 patients with non-insulin-dependent diabetes mellitus (NIDDM). Albumin excretion was in the microalbuminuric range (alb/Cr ratio > 5.4-40.3) in 112 (23.8%) and in the macroalbuminuric range (alb/Cr ratio > 40.3 mg/mmol) in 89 patients (18.9%). Fourteen percent (n = 67) of patients had a normal plasma HbA1 (< or = 8.5%) while 27% (n = 127) had a normal plasma fructosamine concentration (< or = 2.2 mmol/l). Using stepwise multiple regression analysis, plasma fructosamine concentration was found to be independently and negatively associated with urine albumin/creatinine ratio (B = 0.24, P < 0.006) in the macroalbuminuric group. Further analysis of the relationship between plasma albumin concentration and indices of glycaemic control showed that plasma albumin concentration correlated negatively with random plasma glucose concentration in the normoalbuminuric patients (r = -0.16, P = 0.008) but not in microalbuminuric or macroalbuminuric groups. HbA1 was not correlated with plasma albumin concentration. Our results indicate that albuminuria has an effect on the plasma fructosamine concentration which is independent of plasma albumin concentration.

Glycated haemoglobin: an assessment of high capacity liquid chromatographic and immunoassay methods

We have assessed five high-throughput systems for the measurement of glycated haemoglobin and have reviewed published evaluations of individual analysers. All systems offered better precision than a widely used electroendosmosis method. The low pressure chromatography and immunoassay systems demonstrated greater between-batch imprecision than the high performance liquid chromatography analysers, the latter achieving the proposed analytical goal of between-batch coefficients of variation less than 5%. Agreement between all systems measuring HbA1 was good but there was variability amongst observed HbA1c values. The systems were also assessed for their quality of chromatographic separation, simplicity of operation, flexibility, cost and potential for interference by other haemoglobins.

Collection and storage of capillary blood in glass fibre filters for glycated haemoglobin measurement by a microcolorimetric method

A filter method for collection and storage of capillary blood spots for glycated haemoglobin (gHb) has been developed. Glass fibre filters (GFB) impregnated with 0.8 M boric acid were used to collect and store capillary blood. Haemoglobin from the dried blood spots was eluted into water and determined by Drabkin's method, while gHb in the eluates was determined by the microcolorimetric method. The intraassay coefficients of variation (CVs) were 4.5, 4.5 and 3.1% at 882, 1101 and 1704 pmol HMF/mg Hb, respectively. The corresponding inter-assay CVs were 8.6, 8.6 and 6.3%, respectively. A total of 63 paired capillary and venous blood samples were measured by both the direct and GFB method. The GFB method showed excellent correlation with the direct method (r = 0.948 and r = 0.994) after 7 and 14 days' storage at room temperature. The GFB method will enable prior collection and postage of blood samples by patients.

Within-clinic glycosylated haemoglobin measurement

The performance of the Diamat HPLC analyser (Bio Rad Instruments) was assessed, and the effect of this on-site HbA1 assay on the therapeutic decisions made at the diabetic clinic evaluated. The intra-assay CV for HbA1 at concentrations of 8.3 and 13.4% was 3.8 and 0.4%, respectively, with inter-assay CV of 5.0 and 3.0%. On a single day 82 HbA1 tests on consecutive patients were performed at the clinic. In 43 insulin-treated patients and 79 non-insulin-treated diabetic patients the HbA1 result changed the management decision in 25 and 18% of patients, respectively. The relationship between HbA1 and self blood glucose monitoring (SBGM) results in the previous 6-week period were also evaluated. In 41% of patients with insulin-treated diabetes who produced SBGM diaries there was a discrepancy between categories of blood glucose control, all of these patients having better SBGM than HbA1 values. This study highlights the feasibility and value of a within-clinic HbA1 assay for clinical decision-making and its usefulness in identifying problems of agreement with self-monitored tests.

Comparison of glycosylated fibrinogen, albumin, and haemoglobin as indices of blood glucose control in diabetic patients

The value of glycosylated fibrinogen as an index of short-term diabetic control was compared with indices of long-term (glycosylated haemoglobin) and intermediate-term (glycosylated albumin) diabetic control, respectively. In this study, percentages of these glycosylated proteins and fasting plasma glucose concentration were determined in 95 healthy non-diabetic subjects and 48 diabetic patients (22 well-controlled and 26 poorly-controlled) after an overnight fast. The differences in the percentages of glycosylated fibrinogen, haemoglobin, and albumin between non-diabetic subjects (4.7, 6.4, and 2.0), well-controlled diabetic patients (6.9, 9.5 and 2.9), and poorly-controlled diabetic patients (11.3, 15.8, and 5.1) were statistically significant (p less than 0.05). The percent glycosylated fibrinogen exhibited significant association with severity of hyperglycaemia when diabetic patients were divided by 2, 4, and 6 standard deviations above the mean of fasting plasma glucose of non-diabetic subjects. There were significant correlations between glycosylated fibrinogen and fasting plasma glucose (r = 0.83, p less than 0.001), glycosylated haemoglobin (r = 0.94, p less than 0.001) and glycosylated albumin (r = 0.92, p less than 0.001) for all subjects studied. In ten newly diagnosed diabetic patients after 6 days of treatment, only the decrease in glycosylated fibrinogen (33.4%) was significant (p less than 0.05), but not that of glycosylated haemoglobin (4.8%) or albumin (8.0%). It is suggested that glycosylated fibrinogen provides the clinician with earlier objective evidence of the metabolic response to therapeutic intervention, and might be regarded as a short-term (2-3 days) index of blood glucose control.