Development and characterization of a latex turbidimetric immunoassay using rabbit anti-CRP single-chain Fv antibodies

In this study, we developed and demonstrated a latex turbidimetric immunoassay (LTIA) using latex beads immobilized with rabbit monoclonal single-chain variable fragments (scFvs) selected from an scFv-displayed phage library. Sixty-five different anti-c-reactive protein (anti-CRP) scFv clones were identified after biopanning selection using antigen-coupled multi-lamellar vesicles. By ranking antigen-binding clones using the apparent dissociation rate constant (appkoff) as a sorting index, scFv clones with a dissociation constant (KD free) ranging from 4.07 × 10-9 M to 1.21 × 10-11 M were isolated. Among them, three candidates (R2-6, R2-45, and R3-2) were produced in the culture supernatant at concentrations of 50 mg/L or higher in flask culture and maintained at considerably high antigen-binding activity in immobilized state on the CM5 sensor chip surface. All the scFv-immobilized latexes (scFv-Ltxs) prepared were well-dispersed in 50 mM MOPS at pH 7.0, without additives for dispersion, and their antigen-dependent aggregation was sufficiently detectable. The reactivity of scFv-Ltx to antigen differed among the scFv clones, in particular, R2-45 scFv-Ltx detected the CRP with the highest signal. Furthermore, the reactivity of scFv-Ltx varied significantly with salt concentration, scFv immobilization density, and the type of blocking protein. Particularly, antigen-dependent latex aggregation improved significantly in all rabbit scFv clones when scFv-Ltx was blocked with horse muscle myoglobin compared with conventional bovine serum albumin; while their baseline signals in the absence of antigen were fully stable. Under optimal conditions, R2-45 scFv-Ltx exhibited greater aggregation signals with antigen concentrations higher than those produced by conventional polyclonal antibody-immobilized latex for CRP detection in LTIA. The methodology for rabbit scFv isolation, immobilization, and antigen-dependent latex aggregation demonstrated in the present study can be applicable to scFv-based LTIA for various target antigens.

Additive and Interactive Genetically Contextual Effects of HbA1c on cg19693031 Methylation in Type 2 Diabetes

Type 2 diabetes mellitus (T2D) has a complex genetic and environmental architecture that underlies its development and clinical presentation. Despite the identification of well over a hundred genetic variants and CpG sites that associate with T2D, a robust biosignature that could be used to prevent or forestall clinical disease has not been developed. Based on the premise that underlying genetic variation influences DNA methylation (DNAm) independently of or in combination with environmental exposures, we assessed the ability of local and distal gene x methylation (GxMeth) interactive effects to improve cg19693031 models for predicting T2D status in an African American cohort. Using genome-wide genetic data from 506 subjects, we identified a total of 1476 GxMeth terms associated with HbA1c values. The GxMeth SNPs map to biological pathways associated with the development and complications of T2D, with genetically contextual differences in methylation observed only in diabetic subjects for two GxMeth SNPs (rs2390998 AG vs. GG, p = 4.63 × 10−11, Δβ = 13%, effect size = 0.16 [95% CI = 0.05, 0.32]; rs1074390 AA vs. GG, p = 3.93 × 10−4, Δβ = 9%, effect size = 0.38 [95% CI = 0.12, 0.56]. Using a repeated stratified k-fold cross-validation approach, a series of balanced random forest classifiers with random under-sampling were built to evaluate the addition of GxMeth terms to cg19693031 models to discriminate between normoglycemic controls versus T2D subjects. The results were compared to those obtained from models incorporating only the covariates (age, sex and BMI) and the addition of cg19693031. We found a post-pruned classifier incorporating 10 GxMeth SNPs and cg19693031 adjusted for covariates predicted the T2D status, with the AUC, sensitivity, specificity and precision of the positive target class being 0.76, 0.81, 0.70 and 0.63, respectively. Comparatively, the AUC, sensitivity, specificity and precision using the covariates and cg19693031 were only 0.71, 0.74, 0.67 and 0.59, respectively. Collectively, we demonstrate correcting for genetic confounding of cg19693031 improves its ability to detect type 2 diabetes. We conclude that an integrated genetic–epigenetic approach could inform personalized medicine programming for more effective prevention and treatment of T2D.

Effects of exercise intensity on gut microbiome composition and function in people with type 2 diabetes

Exercise is positively associated with higher microbial diversity, but there is limited information on exercise intensity's effect on gut microbiome composition and function in clinical populations. This study examines whether different intensities of exercise exert differential effects on gut microbiome composition and function in low active people with type 2 diabetes.This is a sub-study of the Exercise for Type 2 Diabetes Study, a single centre, prospective, randomised controlled trial. Participants (n=12) completed 8-weeks of combined aerobic and resistance moderate intensity continuous training (C-MICT) or combined aerobic and resistance high-intensity interval training (C-HIIT). Faecal samples were collected before and after intervention to measure gut microbiome composition and metabolic pathways (metagenome shotgun sequencing) and short-chain fatty acids.Post-exercise α-diversity was different between groups as was the relative abundance of specific taxa was (p<0.05). Post-exercise relative abundance of Bifidobacterium, A. municiphila, and butyrate-producers Lachnospira eligens, Enterococcus spp., and Clostridium Cluster IV were higher at lower exercise intensity. Other butyrate-producers (from Eryspelothrichales and Oscillospirales), and methane producer Methanobrevibacter smithii were higher at higher exercise intensity. Pyruvate metabolism (ko00620),COG 'Cell wall membrane envelope biogenesis' and 'Unknown function' pathways were significantly different between groups and higher in C-MICT post-exercise. Differential abundance analysis on KO showed higher expression of Two-component system in C-HIIT. Transcription factors and 'unknown metabolism' related pathways decreased in both groups. There were no significant between group changes in faecal short chain fatty acids.Exercise intensity had a distinct effect on gut microbiome abundance and metabolic function, without impacting short-chain fatty acid outputTrial registration: Australian New Zealand Clinical Trials Registry identifier: ACTRN12615000475549..

A study to correlate effect of dietary modification on biochemical and cardiovascular parameters among prediabetics

Objectives:

Dietary factors are important in the prevention and treatment of prediabetes and diabetes mellitus (DM). This study was designed to evaluate the prevalence, associated risk factors, dietary modification, and calories consumption calculated by the food frequency questionnaire and correlate them with the metabolic parameters, namely blood glucose, HbA1c, lipid profile, and cardiovascular parameters as heart rate variability and carotid intima media thickness (CIMT) among the prediabetics.

Methods:

An experimental interventional study was carried out in the Department of Physiology and Medicine at the RUHS College of Medical Sciences and Associated Group of Hospitals. The assessments were done at baseline and after 6 months of post-dietary modification. The total duration of the study was 6 months. A total of 250 prediabetic subjects were enrolled. Study Group A (n = 125) was engaged in dietary modification, whereas Group B (n = 125) was considered as control. The dietary assessment was done by a food frequency questionnaire.

Result:

After dietary modification, a decrease in the body mass index (1.3%), systolic blood pressure (3.1%), diastolic blood pressure (3.1%), blood glucose (2.8%), triglyceride (2.8%), high density lipoprotein (0.9%), HbA1c (2%), cholesterol (1.4%), and low-frequency/high-frequency ratios (1%), carotid intima media thickness (1.6%), as compared to control, was noticed after 6 months of dietary modification.

Conclusion:

This study suggested that prediabetics required health education including nutritional education as diet modification can play an important role to encourage diabetes-onset prevention and its related complications. The health-care providers and workers should increase the awareness about the importance of diet and encourage the prediabetics toward a healthy lifestyle, which may help in the quality of life and appropriate self-care, primary prevention of diabetes and its complications.

CTRI Registration:

CTRI/2017/06/008825.

Method comparison of Particle Enhanced Immunoturbidimetry (PEIT) with High Performance Liquid Chromatography (HPLC) for glycated hemoglobin (HbA1c) analysis

BACKGROUND AND OBJECTIVE

High Performance Liquid Chromatography (HPLC) technique is considered as a gold standard for HbA1c analysis however all laboratories cannot adopt it due to certain limitations. Our aim was to compare Particle Enhanced Immunoturbidimetry (PEIT) method with High Performance Liquid Chromatography (HPLC) for HbA1c analysis.

METHOD

All blood samples were analyzed by HPLC assay on a Bio-Rad D-10 analyzer and PEIT on an Erba XL-200 analyzer. Precision studies were undertaken and Coefficient of Variation (%CV) calculated. Systemic Error (SE), Random Error (RE) and Total Error (TE_calc) were obtained. The Total Allowable Error (TEa) set by the National Glycohemoglobin Standardization Program (NGSP) for HbA1c is 6%.The acceptable evaluation method is where TE_calc is less than TE_a. RESULTS: The Precision studies were satisfactory with Coefficient of Variation (%CV) being less than 4% for both techniques. Mean HbA1c levels were slightly higher from HPLC than PEIT 9.07 ± 2.23% and 8.93 ± 2.10% respectively, although the difference was minimal. RE was 1.41%, TE_calc was 1.55%, which was less than TEa set by the NGSP. Both methods strongly correlated with the correlation coefficient (r) 0.9716, p < 0.0001.

CONCLUSION

Our study showed HbA1c analysis by PEIT technique is precise, accurate, rapid and convenient and can be employed as an alternative to HPLC technique in countries where cost is a major problem for diagnosis and treatment.

Associations of Arginine with Gestational Diabetes Mellitus in a Follow-Up Study

In the reported study we applied the targeted metabolomic profiling employing high pressure liquid chromatography coupled with triple quadrupole tandem mass spectrometry (HPLC–MS/MS) to understand the pathophysiology of gestational diabetes mellitus (GDM), early identification of women who are at risk of developing GDM, and the differences in recovery postpartum between these women and normoglycemic women. We profiled the peripheral blood from patients during the second trimester of pregnancy and three months, and one year postpartum. In the GDM group Arg, Gln, His, Met, Phe and Ser were downregulated with statistical significance in comparison to normoglycemic (NGT) women. From the analysis of the association of all amino acid profiles of GDM and NGT women, several statistical models predicting diabetic status were formulated and compared with the literature, with the arginine-based model as the most promising of the screened ones (area under the curve (AUC) = 0.749). Our research results have shed light on the critical role of arginine in the development of GDM and may help in precisely distinguishing between GDM and NGT and earlier detection of GDM but also in predicting women with the increased type 2 diabetes mellitus (T2DM) risk.

New Validated Method for Quantification of Glycated Hemoglobin by LC-QToF-MS: Is HRMS Able to Quantify Clinical Samples?

High-resolution mass spectrometry is a powerful tool in clinical analysis but remains less explored due to its lower dynamic range and sensitivity compared to triple quadrupoles. Glycated hemoglobin (HbA1c) is the current gold standard biomarker to monitor the control of diabetes, representing long-term plasma glycemic levels. Due to its clinical importance, several methods have been developed for HbA1c quantification, using different principles; however, the results obtained with these techniques may differ according to the method adopted. Hence, there is a great need to standardize the current methods to quantify glycated hemoglobin. A new UPLC-QToF-MS method was fully validated and tested to quantify HbA1c in human samples. The peptides VHLTPE m/z 695.373 and gly-VHLTPE m/z 857.426, obtained via Glu-C digestion, were the selected peptides for quantification of HbA1c (mmol/mol). Chromatographic separation was obtained in a C18 column, maintained at 40 °C. The mobile phase was composed of water and acetonitrile, both containing 0.02% TFA and 0.1% acetic acid, and eluted in gradient mode. The method was fully validated, being considered linear in the range of 25-107 mmol/mol of HbA1c, and was sensitive, selective, precise, accurate, and free of matrix and carryover effects. The method was successfully applied to real samples, reaching about 90% agreement with reference method results, providing accurate and precise information on peptide mass, without laborious sample preparation. These results support the use of HRMS to improve the quality of quantitative results of HbA1c in health services and demonstrate a possible application of peptide investigation for clinical analysis in the near future.

Effects of switching to low-dose rosuvastatin (5 mg/day) on glucose metabolism and lipid profiles in Japanese patients with type 2 diabetes and dyslipidemia: a single-arm, prospective, interventional trial

Aims

We investigated the effects of switching from other statins, such as pravastatin (5 or 10 mg/day), rosuvastatin (2.5 mg/day), or pitavastatin (1 or 2 mg/day), to low-dose rosuvastatin (5 mg/day) on glucose metabolism and lipid profiles in Japanese patients with type 2 diabetes and dyslipidemia.

Methods

This was a prospective, two-center, open-label, single-arm, interventional trial. Several clinical parameters were analyzed at baseline and 24 weeks after switching from other statins to rosuvastatin at 5 mg/day. The primary endpoints were changes in hemoglobin (Hb) A1c level and lipid profile.

Results

Forty-five patients were enrolled in the trial. The mean HbA1c level increased significantly from 7.1 ± 0.7 to 7.5 ± 0.9% (P < 0.001), whereas the mean low-density lipoprotein cholesterol (LDL-C) level decreased significantly from 108.9 ± 16.5 to 91.6 ± 24.5 mg/dL (P < 0.001). Multiple linear regression analysis showed that changes in HbA1c levels were significantly and positively correlated with fasting plasma glucose (FPG) levels at baseline. Receiver operating characteristic (ROC) curve analysis examining the relationship between HbA1c and FPG showed that FPG was a significant predictor of changes in HbA1c levels (area under the curve, 0.72). The cutoff FPG value of 168 mg/dL had a sensitivity of 47% and a specificity of 93%.

Conclusions

Switching to a low dose of rosuvastatin impaired glucose metabolism in Japanese patients with type 2 diabetes and dyslipidemia. Patients with high FPG levels were particularly prone to an exacerbation of glucose metabolism.

The changing relationship between HbA1c and FPG according to different FPG ranges

PURPOSE

Since the American Diabetes Association included hemoglobin A1c (HbA1c) in the diagnostic criteria for diabetes in 2010, the clinical use of HbA1c has remained controversial. We explored the use of HbA1c for diagnosing diabetes and intermediate hyperglycemia in comparison with fasting plasma glucose (FPG).

METHODS

We screened 3710 adult subjects (mean age = 55.24 years) comprising 1704 males and 2006 females. We drew an receiver operating characteristic (ROC) curve to evaluate the ability of HbA1c to diagnose diabetes and intermediate hyperglycemia according to FPG. We used Kappa coefficient and Pearson's correlation coefficient to evaluate the relationship between HbA1c and FPG in different FPG ranges.

RESULTS

The areas under ROC curve to diagnose diabetes and intermediate hyperglycemia were 0.859 (95 % CI 0.827-0.892) and 0.633 (95 % CI 0.615-0.651). The kappa coefficients between FPG and HbA1c for diagnosis of diabetes and intermediate hyperglycemia were 0.601 (P < 0.001) and 0.104 (P < 0.001). The Pearson's correlation coefficient of FPG and HbA1c was 0.640 (P < 0.001), but when we classified FPG as normal, intermediate hyperglycemia and diabetes, the coefficients became 0.07 (P = 0.002), 0.185 (P < 0.001) and 0.760 (P < 0.001), respectively.

CONCLUSIONS

The relationship between HbA1c and FPG changed according to the different FPG ranges. When FPG was higher, the relationship was stronger. HbA1c and FPG were highly consistent in diagnosing diabetes, but they were not in predicting intermediate hyperglycemia.

Significance of HbA1c Test in Diagnosis and Prognosis of Diabetic Patients

Diabetes is a global endemic with rapidly increasing prevalence in both developing and developed countries. The American Diabetes Association has recommended glycated hemoglobin (HbA1c) as a possible substitute to fasting blood glucose for diagnosis of diabetes. HbA1c is an important indicator of long-term glycemic control with the ability to reflect the cumulative glycemic history of the preceding two to three months. HbA1c not only provides a reliable measure of chronic hyperglycemia but also correlates well with the risk of long-term diabetes complications. Elevated HbA1c has also been regarded as an independent risk factor for coronary heart disease and stroke in subjects with or without diabetes. The valuable information provided by a single HbA1c test has rendered it as a reliable biomarker for the diagnosis and prognosis of diabetes. This review highlights the role of HbA1c in diagnosis and prognosis of diabetes patients.

Genetic Predisposition to Diabetic Nephropathy: Evidence for a Role of ACE (I/D) Gene Polymorphism in Type 2 Diabetic Population from Kutch Region

Genetic polymorphism as described with angiotensin-converting enzyme gene has been proposed as a putative mediator of diabetic nephropathy. We substantiate the hypothesis that genetic variants of the ACE have significant impacts on diabetic nephropathy. To assess the possible association between the three ACE polymorphic variants and DN in an ethnically homogeneous type 2 diabetic population from Kutch region. A 287-bp insertion/deletion polymorphism in intron 16 of the ACE gene was examined by polymerase chain reaction using a case-control approach conducted with 309 unrelated type 2 diabetic patients of Kutch origin (159 Ahir and 150 Rabari, with >10 years duration of T2DM). Of the patients, 143 had nephropathy {AER >30 mg/day (Ahir, n:73 and Rabari, n:70)} and were considered as cases; all others {n:166 (86 Ahir and 80 Rabari)} were normoalbuminuric (AER <30 mg/day) and were treated as controls. Suitable descriptive statistics was used for different variables. Genotype frequencies in all groups were all in accordance with the Hardy-Weinberg equilibrium. Genotypic distribution was significantly different between cases and controls (Ahir: x(2) :8.87, 2 d.f. p = 0.0118; Rabari: x(2) :11.01, 2 d.f. p = 0.0041). Multivariate logistic regression analysis revealed that DD genotype was a significant and strongest independent predictor of microalbuminuria (Ahir: p = 0.0362, OR = 2.65, 95 % CI 1.89-6.36; Rabari: p = 0.024, OR = 2.81, 95 % CI 1.9-6.65). However, it did not independently change the odds of having macroalbuminuria versus microalbuminuria. Analysis of the association under various genetic models revealed that ACE I/D polymorphic variant contribute to DN susceptibility under recessive mode only. Genetic variation at the ACE locus as D/D variant in intron 16, contribute to an increased risk of nephropathy in T2DM patients but not extent of DN severity, and thus this polymorphism might be considered as genetic risk factors for DN among patients with type 2 diabetes.

The elevated gene expression level of the A(2B) adenosine receptor is associated with hyperglycemia in women with gestational diabetes mellitus

BACKGROUND

Adenosine receptors denoted by A1 , A2A , A2B , and A3 and encoded by ADORA1, ADORA2A, ADORA2B, and ADORA3 genes, respectively, are adenosine-activated G-protein-coupled receptors that play an important role in obesity and type 2 diabetes mellitus. However, little is known about their significance in gestational diabetes mellitus (GDM). The purpose of this study was to investigate whether there are changes in leukocyte AR expression in GDM patients and whether these alterations are linked to well-known diabetic genes.

METHODS

Leukocytes were isolated from the blood of normal glucose tolerant (NGT; n = 35) and GDM (n = 82) pregnant women, and expression of ARs was determined by a semi-quantitative polymerase chain reaction (PCR). Univariate correlation analysis was performed to investigate associations between expression of ARs and anthropometric and metabolic parameters of patients. Furthermore, the identification of diabetic genes linked to significantly differentiated leukocyte adenosine receptors expression in GDM women was also carried out with the use of the human diabetes RT(2) profiler PCR arrays.

RESULTS

ADORA2B mRNA expression was significantly higher in GDM versus NGT pregnant women (p < 0.05), and positively correlated with the glucose level at 1-h 75-g oral glucose tolerance test (OGTT; r = 0.21, p = 0.044). Nineteen diabetic genes linked to leukocyte ADORA2B overexpression associated with hyperglycemia in GDM women were also identified.

CONCLUSIONS

Maternal leukocyte ADORA2B overexpression is associated with hyperglycemia in GDM subjects, and it is accompanied by complex alterations in the expression of diabetes-related genes involved in insulin action, carbohydrate and lipid metabolism, oxidative stress, and inflammation.

Dyslipidemia associated with poor glycemic control in type 2 diabetes mellitus and the protective effect of metformin supplementation

The nature of the dyslipidemia associated with diabetes mellitus is complex and is the major risk factor for atherosclerosis and coronary artery disease. Aim of this study was to assess the effect of glycemic control, achieved by metformin, glibenclamide and insulin, on lipid profile in type 2 diabetic patients. One hundred and sixty-five type 2 diabetes mellitus patients were classified into good glycemic control (Group I) and poor glycemic control (Group II) on the basis of their blood HbA1c values. The Group II was characterized with high serum triglyceride (190.46 ± 15.20 mg/dl), total cholesterol (175.3 ± 6.31 mg/dl) as well as high LDL-cholesterol (109.0 ± 5.88 mg/dl). Significant correlations were evident between HbA1c and dyslipidemia, particularly serum TG (r = 0.28, P < 0.05), and between HbA1c and total cholesterol (r = 0.310, P < 0.05). Better glycemic control and improved dyslipidemia were observed in patients on combination therapy of metformin plus glibenclamide.

Passive adsorption of human antirrabic immunoglobulin onto a polystyrene surface

The latex agglutination immunoassay technique uses polymer colloids as carriers of adsorbed proteins to enhance the antigen-antibody reaction. The aim of the present work is to study the adsorption of Human Antirrabic Immunoglobulin (HA-IgG) on polystyrene latex (PS). The physical adsorption of HA-IgG on PS latex was investigated as a function of pH at 2 mM ionic strength. The amount of HA-IgG adsorbed onto PS latex greatly depends on pH; its value showed a maximum in the neighborhood of the IEP of HA-IgG. The electrophoretic method was applied to characterize latex particles. The influence of the amount of HA-IgG adsorbed (J(ads)) on the electrophoretic mobility and zeta-potential values was also studied.

Comparative performance of lab tests and blood testing device to monitor glucose, total cholesterol and triacylglycerol in type 2 diabetic patients

The performance of lab tests (LT) and blood testing devices (BTD) to monitor glycemia vs. glycated hemoglobin A1c (A1c) were compared. In addition, the performance of blood glucose, total cholesterol (TC) and triacylglycerol measured by LT and BDT were compared. All parameters were measured based on the same blood samples from overnight fasted type 2 diabetic patients (T2DP). Linear regression analysis was used for all comparisons. The results showed that A1c correlated better with LT-glucose (r = 0.58) than BTD-glucose (r = 0.42). Moreover, LT vs. BTD showed r values of 0.90, 0.82 and 0.92 for glucose, TC and triacylglycerol, respectively. It was concluded that the performance of LT-glucose was better than BDT-glucose. Moreover, since triacylycerol and TC measured by BTD correlated better with LT compared to BDT-glucose vs. LT-glucose, the inclusion of BTD-TC and BTD-triacylglycerol for detecting and monitoring hyperlipidemia in T2DP should be considered.

Selective electrochemical sensing of glycated hemoglobin (HbA1c) on thiophene-3-boronic acid self-assembled monolayer covered gold electrodes

We report a novel concept of sensing glycated hemoglobin, HbA 1c, which is now the most important index for a long-term average blood glucose level, by first selectively immobilizing it on the thiophene-3-boronic acid (T3BA) self-assembled monolayer (SAM)-covered gold electrode by a selective chemical reaction with boronic acid. HbA 1c thus immobilized is then detected by the label-free electrochemical impedance spectroscopic (EIS) measurements with a redox probe, an equimolar mixture of K 3Fe(CN) 6 and K 4Fe(CN) 6, present. The rate of charge transfer between the electrode and the redox probe is shown to be modulated by the amount of HbA 1c in the matrix hemoglobin solution due to the blocking effect caused by the binding of HbA 1c with boronic acid. Both the formation of a well-defined T3BA-SAM on the gold surface and the chemical binding of its boronic acid with HbA 1c in solution were confirmed by quartz crystal microbalance, atomic force microscopy, and EIS experiments.

Electrochemical detection of HbA1c, a maker for diabetes, using a flow immunoassay system

An on-chip electrochemical flow immunoassay system for the detection of hemoglobin A1c (HbA1c) was developed using anti-human hemoglobin (Hb) IgG labeled with ferrocene monocarboxylic acid (Fc-COOH) and boronate-affinity chromatography. An on-chip column packed with boronate-activated agarose beads was used for the separation of HbA1c from both non-glycated Hb and free antibody. Anti-human Hb IgG conjugated to Fc-COOH (Fc-IgG) was used for the electrochemical detection of HbA1c. The assay procedure included immunoreactions with Fc-IgG and HbA1c, separation of immunocomplexes by boronate affinity, and electrochemical detection of Fc-IgG-HbA1c immunocomplexes. The immunoreaction mixtures were injected onto a boronate-affinity column. HbA1c-antibody complexes were then trapped onto the column by the affinity of HbA1c to boronic acid. Subsequently, elution buffer containing sorbitol was applied to elute HbA1c-antibody complexes and a current was detected by applying 600 mV versus Ag/AgCl. The elution signal was an estimation of the HbA1c amount. A linear correlation between the increase of current and HbA1c concentration was obtained up to an HbA1c concentration of 500 microg/ml. The HbA1c flow immunoassay was successfully achieved using hemolysates. This electrochemical flow immunoassay system enabled us to construct a novel point-of-care testing device for the monitoring of glycated proteins including HbA1c.

New enzymatic assay for glycohemoglobin

BACKGROUND

Previous methods to measure glycohemoglobin (GHb) have been time-consuming or imprecise; we therefore developed a new enzymatic assay for GHb.

METHODS

Blood cells were first hemolyzed, and hemoglobin was digested with protease to yield fructosyl amino acid. Fructosyl amino acid oxidase acts on the fructosyl amino acid and generates hydrogen peroxide, which reacts with chromogens in the presence of peroxidase. Total hemoglobin was measured spectrometrically in the same reaction tube. The results were reported as the ratio of the concentrations of GHb and hemoglobin.

RESULTS

The measured values were comparable to those determined with a HPLC method and with an immunoassay in blood samples from 2854 patients with diabetes. Regression analysis for the enzymatic assay (y) vs the HPLC method (x) produced the following: r = 0.979; slope, 0.994 [95% confidence interval (CI), 0.986-1.001]; y-intercept, 0.04% (95% CI, -0.09% to 0.01%); n = 2854. For the enzymatic assay (y) vs the immunoassay (x), the regression statistics were as follows: r = 0.982; slope, 1.002 (95% CI, 0.995-1.009); y-intercept, 0% (95% CI, -0.05% to 0.05%); n = 2854.

CONCLUSIONS

The values measured by the new enzymatic assay are sufficiently correlated with those of the conventional HPLC method and immunoassay, but the proposed assay for GHb is rapid and has high precision.

Use of Home Hemoglobin A1c Test Kits to Monitor the Effectiveness of Diabetes Care

BACKGROUND

Periodic measurement of glycated hemoglobin (HbA1c) is highly recommended for people with diabetes to determine whether their blood glucose is adequately controlled. Quality improvement programs initiated by health plans often focus on ensuring that HbA1c is being monitored in members with diabetes. To focus improvement efforts on members with poor blood glucose control, health plans need to know which members have high HbA1c levels. Recent development of home test kits provides another opportunity for health plans to help members measure their HbA1c and to identify members with high levels.

METHODS

A sample of members from two health plans who were sent HbA1c self-test kits in January 2000 participated in a telephone interview. To understand why members did or did not use self-test kits sent by their health plans, the survey focused on perceived ease of use, outcomes, and normative beliefs.

RESULTS

In the group of 380 members who were interviewed, 170 (45%) used the kit. HbA1c values were > 8 mg/dl in 43%. Among the 170 who used the kit, 160 said that they would use the kit. Their most common reason for using the kit was to find out how well their blood glucose was being controlled (48%). Convenience (12%) was the next most frequent reason for using the kit. Among the 210 members who did not use the kit, 81 members said that they would not or were not sure if they would when interviewed. Their most frequent reason for not using the kit was duplication of tests done by physicians (34%). Others were too busy (12%), wanted to talk with their physician (11%), or had difficulty using the kit (11%).

CONCLUSIONS

Because the majority of health plan members did not use the kit and the majority who did use the kit had HbA1c levels < 8 mg/dl, sending home test kits to members did not result in a high yield of members with elevated HbA1c levels. Physicians' support for use of the kits and efforts to make kits easier to use might increase use. Efforts to avoid duplication of physicians' measurements could make this strategy to identify members with poorly controlled levels of blood glucose more cost-effective, although health plans would not know which monitored members might benefit most from programs to improve care of diabetes.

Effects of Hemoglobin Variants and Chemically Modified Derivatives on Assays for Glycohemoglobin

Background: Glycohemoglobin (gHb), measured as hemoglobin (Hb) A1c or as total gHb, provides a common means for assessing long-term glycemic control in individuals with diabetes mellitus. Genetic variants and chemically modified derivatives of Hb can profoundly affect the accuracy of these measurements, although effects vary considerably among commercially available methods. The prevalence of genetic variants such as HbS, HbC, and HbE, and chemically modified derivatives such as carbamyl-Hb among patient populations undergoing testing is not insignificant. Clinical laboratories and sites responsible for point-of-care testing of gHb need to be aware of the interferences produced in assays by these Hbs.

Approach: We conducted a review of the literature describing the effects of variant Hbs on gHb assay methods commonly used in clinical laboratories.

Content: This review summarizes the documented effects of both common and uncommon Hb variants and derivatives on the measurement of gHb. Where known, we discuss mechanisms of interference on specific assays and methodologies. We specifically address effects of commonly encountered Hbs, such as carbamyl-Hb, HbS, HbC, HbE, and HbF, on assays that use cation-exchange chromatography, immunoassays, or boronate affinity methods for measuring gHb.

Summary: A variety of patient- and laboratory-related factors can adversely affect the measurement of gHb in patients harboring Hb variants or derivatives. Identification of the variant or derivative Hb before or during testing may allow accurate measurement of gHb by the selection of a method unaffected by the given variant or derivative. However, laboratories should make available alternative, non-Hb-based methods for assessing long-term glycemic control in individuals with HbCC, HbSS, or HbSC disease, or with other underlying disorders where the concentration of gHb does not accurately reflect long-term glycemic control.