The IFCC Reference Measurement System for HbA1c: A 6-Year Progress Report

The effect of anaemia and abnormalities of erythrocyte indices on HbA1c analysis: a systematic review

AIMS/HYPOTHESIS

The use of HbA1c for the diagnosis of diabetes is now widely advocated despite caveats to its use. Anaemia is cited as a major confounder to this use; however, the effect of erythrocyte indices and to what degree anaemia influences HbA1c levels is not known.

METHODS

A systematic electronic database search of MEDLINE, EMBASE, the Cumulative Index to Nursing & Allied Health Literature (CINAHL) and the Cochrane Library was conducted for relevant articles published between January 1990 and May 2014. Included studies had at least one measurement of HbA1c and glucose, and a least one index of haematinic deficiency, involving non-pregnant adults, not known to have diabetes.

RESULTS

A total of 12 articles from 544 were included. The majority of studies focused on iron deficiency anaemia (IDA) and, in general, demonstrated that the presence of iron deficiency with or without anaemia led to an increase in HbA1c values compared with controls, with no concomitant rise in glucose indices. Data on the effects of other indices of erythrocyte abnormalities on HbA1c are limited but show a possible decrease in HbA1c values with non-iron deficiency forms of anaemia.

CONCLUSIONS/INTERPRETATION

HbA1c is likely to be affected by iron deficiency and IDA with a spurious increase in HbA1c values; conversely, non-IDA may lead to a decreased HbA1c value. This may lead to confusion when diagnosing diabetes using HbA1c. This review clearly identifies the need for more evidence, especially in identifying the types and degrees of anaemia likely to have significant impact on the reliability of HbA1c.

C-peptide immunoreactivity index is associated with improvement of HbA1c: 2-Year follow-up of sitagliptin use in patients with type 2 diabetes

AIMS

This retrospective study aimed to determine the hypoglycaemic effect of 2 years of sitagliptin administration in terms of changes in HbA1c and C-peptide immunoreactivity (CPR) index (plasma CPR [ng/mL]/glucose [mg/dL]×100).

METHODS

The inclusion criteria for DPP-4 inhibitor-naive outpatients with type 2 diabetes (n=285) were: continuation of sitagliptin for ≥700 days from initial administration and measurement of HbA1c, serum CPR, and plasma glucose levels at 0, 3, 6, 12, 18, and 24 months after sitagliptin initiation. Logistic regression analyses determined the factors contributing to the response to sitagliptin, based on responder (ΔHbA1c ≤-0.4% [≤-4 mmol/mol]) and non-responder (ΔHbA1c >-0.4% [>-4 mmol/mol]) groups.

RESULTS

The HbA1c level decreased and CPR index increased from baseline to 3, 6, 12, 18, and 24 months after the start of sitagliptin administration (HbA1c: 7.4 ± 0.8% [57 ± 9 mmol/mol], 7.3 ± 0.9% [57 ± 9 mmol/mol], 7.4 ± 0.9% [58 ± 10 mmol/mol], 7.1 ± 0.8% [55 ± 9 mmol/mol], and 7.3 ± 0.9% [57 ± 10 mmol/mol], respectively, all P<0.001 vs. baseline [8.0 ± 1.0%, 64 ± 11 mmol/mol] and CPR index: 1.69 ± 0.96, 1.71 ± 1.10, 1.62 ± 0.96, 1.64 ± 0.92, and 1.66 ± 0.96, respectively, all P<0.05 vs. baseline [1.47 ± 0.81]). Higher baseline HbA1c level, shorter diabetes duration, and greater CPR index increase after sitagliptin administration were associated with the response to sitagliptin.

CONCLUSIONS

Our results suggest that sitagliptin improves glycaemic control via an improved intrinsic insulin response.

Cardiometabolic Risk, Socio-Psychological Factors, and Trajectory of Grip Strength Among Older Japanese Adults

OBJECTIVE

To examine the association between cardiometabolic risk (percent body fat [BF%], triglycerides [TG], high-density lipoprotein [HDL]-cholesterol, hemoglobin A1c [HbA1c]), socio-psychological factors (education and self-rated health [SRH]), and trajectories of grip strength (GS) in older adults.

METHOD

Longitudinal 8-year data from 1,381 Japanese adults aged 65 years or above were analyzed using hierarchical linear models, stratified according to gender.

RESULTS

GS declined following a linear trajectory. In both genders, higher BF% was associated with weaker GS, but not with the rate of decline. GS trajectory did not correlate with baseline TG, HDL-C, or HbA1c. Cardiometabolic factors mediated educational differences in GS intercept in both genders. In women, better SRH predicted stronger GS. The effect of SRH was robust to adjustments for cardiometabolic risk.

DISCUSSION

In older adults, GS and its rate of decline are selectively associated with both cardiometabolic risk and socio-psychological characteristics. Cardiometabolic risk mediates educational disparities in GS but not differences in subjective assessments of health.

Alpha-lipoic acid modifies circulating angiogenic factors in patients with type 2 diabetes mellitus

AIMS

In recent years interest has been focused on angiogenesis as a process involved in coronary artery disease (CAD) and diabetic distal sensorimotor polyneuropathy (DSPN). Recent studies have demonstrated the possible angiogenesis-modulating potential of alpha-lipoic acid (ALA) for DSPN and CAD. The aim of our study was to investigate the influence of ALA on serum angiogenic factors in patients with DM-2 (type 2 diabetes) with CAD and DSPN.

METHODS

Sixty patients with type 2 DM (T2DM) and CAD and 25 non-diabetic subjects were studied. Thirty patients with T2DM, CAD and DSPN were given 600 mg of ALA a day for 90 days. VEGF, bFGF, MCP-1, angiogenin, IL-12 and IL-10 concentrations in the sera were measured by flow cytometry.

RESULTS

ALA significantly increased VEGF, bFGF and IL-10 and decreased MCP-1 serum concentrations in patients with T2DM and CAD and DSPN. VEGF and IL-10 serum levels, both before and after ALA-treatment, were higher in this group than in T2DM and CAD patients, while circulating bFGF was higher and MCP-1 serum level lower in patients with T2DM and CAD and DSPN only in the post-ALA-treatment, compared to the T2DM and CAD group.

CONCLUSIONS

ALA may influence angiogenesis in type 2 diabetic patients through an effect on some circulating factors including VEGF, bFGF, MCP-1 and IL-10.

Empirical mode decomposition analysis of near-infrared spectroscopy muscular signals to assess the effect of physical activity in type 2 diabetic patients

Type 2 diabetes is a metabolic disorder that may cause major problems to several physiological systems. Exercise has proven to be very effective in the prevention, management and improvement of this pathology in patients. Muscle metabolism is often studied with near-infrared spectroscopy (NIRS), a noninvasive technique that can measure changes in the concentration of oxygenated (O2Hb) and reduced hemoglobin (HHb) of tissues. These NIRS signals are highly non-stationary, non-Gaussian and nonlinear in nature. The empirical mode decomposition (EMD) is used as a nonlinear adaptive model to extract information present in the NIRS signals. NIRS signals acquired from the tibialis anterior muscle of controls and type 2 diabetic patients are processed by EMD to yield three intrinsic mode functions (IMF). The sample entropy (SE), fractal dimension (FD), and Hurst exponent (HE) are computed from these IMFs. Subjects are monitored at the beginning of the study and after one year of a physical training programme. Following the exercise programme, we observed an increase in the SE and FD and a decrease in the HE in all diabetic subjects. Our results show the influence of physical exercise program in improving muscle performance and muscle drive by the central nervous system in the patients. A multivariate analysis of variance performed at the end of the training programme also indicated that the NIRS metabolic patterns of controls and diabetic subjects are more similar than at the beginning of the study. Hence, the proposed EMD technique applied to NIRS signals may be very useful to gain a non-invasive understanding of the neuromuscular and vascular impairment in diabetic subjects.

The ratio of glycated albumin to hemoglobin A1c measured in IFCC units accurately represents the glycation gap

The glycation gap (G-gap: difference between measured hemoglobin A1c [A1C] and the value predicted by its regression on the fructosamine level) is stable and associated with diabetic complications. Measuring A1C level in International Federation of Clinical Chemistry (IFCC) units (A1C-SI; mmol/mol) and National Glycohemoglobin Standardization Program units (A1C-NGSP; %) and using glycated albumin (GA) level instead of fructosamine level for calculating the G-gap, we investigated whether the G-gap is better represented by GA/A1C ratio if expressed in SI units (GA/A1C-SI ratio) rather than in NGSP units (GA/A1C-% ratio). We examined 749 Japanese children with type 1 diabetes using simultaneous GA and A1C measurements. Of these, 369 patients were examined more than five times to assess the consistency of the G-gap and the GA/A1C ratio within individuals. The relationship of GA/A1C-% ratio to the corresponding A1C-NGSP was stronger than that of GA/A1C-SI ratio to A1C-IFCC. At enrollment, the inverse relationship between the GA/A1C-SI ratio and G-gap was highly significant (R(2) = 0.95) compared with that between the GA/A1C-% ratio and G-gap (R(2) = 0.69). A highly significant inverse relationship was also observed between the mean GA/A1C-SI ratio and the mean G-gaps obtained individually over time (R(2) = 0.95) compared with that using the corresponding A1C-NGSP (R(2) = 0.67). We conclude that the G-gap is better represented by the GA/A1C-SI ratio. We propose the use of mean GA/A1C-SI ratios easily obtained individually over time as reference values in Japanese children with type 1 diabetes (6.75 ± 0.60 [means ± SD]).

Pharmacokinetic and pharmacodynamic study of ipragliflozin in Japanese patients with type 2 diabetes mellitus: a randomized, double-blind, placebo-controlled study

AIMS

Ipragliflozin is a novel and highly selective sodium-glucose transporter 2 (SGLT2) inhibitor that reduces plasma glucose levels by enhancing urinary glucose excretion in patients with type 2 diabetes mellitus (T2DM). We examined the pharmacokinetic and pharmacodynamic characteristics of two oral doses of ipragliflozin in Japanese patients with T2DM.

METHODS

In this randomized, placebo-controlled, double-blind study, patients were treated with placebo, 50mg or 100mg ipragliflozin once daily for 14 days. Plasma and urine pharmacodynamic parameters were measured on Days -1 and 14, and pharmacokinetic parameters on Day 14. Pharmacodynamic characteristics included area under the curve (AUC) for plasma glucose and insulin for 0-3h (AUC0-3h) and 0-24h (AUC0-24h). Pharmacokinetic characteristics included AUC0-24h, maximum ipragliflozin concentration (Cmax), and time to maximum plasma ipragliflozin concentration (tmax).

RESULTS

Thirty patients were enrolled; 28 were included in pharmacokinetic/pharmacodynamic analyses and 30 in safety analyses. Administration of 50 and 100mg ipragliflozin significantly reduced fasting plasma glucose, as well as the AUC0-3h and AUC0-24h for plasma glucose relative to placebo. Both doses of ipragliflozin also reduced AUC0-24h for insulin, body weight, and glycoalbumin, while urinary glucose excretion increased remarkably. Cmax and AUC0-24h were 1.7- and 1.9-fold higher, respectively, in the 100-mg group than in the 50-mg group.

CONCLUSIONS

Ipragliflozin increased urinary glucose excretion and improved fasting and postprandial glucose, confirming its pharmacokinetic/pharmacodynamic properties in Japanese patients with T2DM.

Misleading hemoglobin A1c levels in a patient with paroxysmal nocturnal hemoglobinuria

OBJECTIVES

We report a case of a patient with diabetes mellitus and unexpectedly low hemoglobin A1c results associated with paroxysmal nocturnal hemoglobinuria (PNH). We review the impact of shortened RBC half-life on the interpretation of hemoglobin A1c levels.

METHODS

Patient history and laboratory test results were obtained from electronic medical records and analyzed.

RESULTS

The patient's hemoglobin A1c declined in parallel to worsening anemia after the diagnosis of PNH. However, elevated serum glucose (random), fructosamine, and glycated albumin suggest ongoing hyperglycemia. Together, these results argue that the decline in hemoglobin A1c was due to decreased RBC survival secondary to PNH.

CONCLUSIONS

Hemoglobin A1c levels must be interpreted with caution in patients with hematologic diseases that change RBC survival. Serum fructosamine and glycated albumin measurements are alternative measures of time-averaged blood glucose control and may be useful in this subset of patients.

Circulating monocyte chemotactic protein 1 (MCP-1), vascular cell adhesion molecule 1 (VCAM-1) and angiogenin in type 2 diabetic patients treated with statins in low doses

Statins are known as agents promoting a biphasic dose-dependent effect on angiogenesis under experimental conditions. Dysregulation of angiogenesis plays an important role in the development of atherosclerosis and it may be affected by metabolic factors. The aim of this research was to explain how low doses of statins modify serum concentrations of pro-angiogenic factors MCP-1 and angiogenin in type 2 diabetic patients. Measurements of metabolic control parameters were performed in 30 patients with type 2 diabetes treated with low doses of statin, and in 34 statin-free patients with type 2 diabetes. The serum levels of MCP-1 and VCAM-1 in statin-treated patients were lower than those of the statin-free group. ANCOVA results revealed that these effects were dependent only on the use of statins. In type 2 diabetic subjects, overall positive correlation was found between total cholesterol or LDL serum concentration and MCP-1 serum level. The angiogenin concentration in the serum did not show differences and was comparable in both groups. The angiogenin serum level correlated negatively with HDL, LDL and with HbA1c. Multivariate regression analysis indicated that angiogenin serum levels in type 2 diabetic patients were determined mainly by HbA1c, HDL-cholesterol and diabetes duration. It has been shown that statins used in low doses in type 2 diabetic subjects decrease MCP-1 and VCAM-1serum levels, most likely due to the statins-related effect on the lipid profile, while angiogenin serum levels in this group are determined rather by the current metabolic control.

A Progress Report of the IFCC Committee for Standardization of Thyroid Function Tests

BACKGROUND

The IFCC Committee for Standardization of Thyroid Function Tests aims at equivalence of laboratory test results for free thyroxine (FT4) and thyrotropin (TSH).

OBJECTIVES

This report describes the phase III method comparison study with clinical samples representing a broad spectrum of thyroid disease. The objective was to expand the feasibility work and explore the impact of standardization/harmonization in the clinically relevant concentration range.

METHODS

Two sets of serum samples (74 for FT4, 94 for TSH) were obtained in a clinical setting. Eight manufacturers participated in the study (with 13 FT4 and 14 TSH assays). Targets for FT4 were set by the international conventional reference measurement procedure of the IFCC; those for TSH were based on the all-procedure trimmed mean. The manufacturers recalibrated their assays against these targets.

RESULTS

All FT4 assays were negatively biased in the mid- to high concentration range, with a maximum interassay discrepancy of approximately 30%. However, in the low range, the maximum deviation was approximately 90%. For TSH, interassay comparability was reasonable in the mid-concentration range, but worse in the pathophysiological ranges. Recalibration was able to eliminate the interassay differences, so that the remaining dispersion of the data was nearly entirely due to within-assay random error components. The impact of recalibration on the numerical results was particularly high for FT4.

CONCLUSIONS

Standardization and harmonization of FT4 and TSH measurements is feasible from a technical point of view. Because of the impact on the numerical values, the implementation needs careful preparation with the stakeholders.

Three of 7 hemoglobin A1c point-of-care instruments do not meet generally accepted analytical performance criteria

BACKGROUND

In 2009, we investigated the conformance of 8 hemoglobin A(1c) (Hb A(1c)) point-of-care (POC) instruments. Since then, instruments have improved and new devices are available on the market. In this second study, we evaluated the performance of DCA Vantage, Afinion, InnovaStar, Quo-Lab, Quo-Test, Cobas B101, and B-analyst Hb A(1c) POC instruments.

METHODS

Clinical and Laboratory Standards Institute protocols EP-5 and EP-9 were applied to investigate imprecision, accuracy, and bias. We assessed bias using the mean of 3 certified secondary reference measurement procedures (SRMPs). Assay conformance with the National Glycohemoglobin Standardization Program (NGSP) certification criteria was also evaluated. Interference of common Hb variants was investigated for methods that could work with hemolysed material.

RESULTS

The total CVs for all instruments, except for the DCA Vantage at a high Hb A(1c) value, were ≤3.1% in SI units and ≤2.1% in Diabetes Control and Complications Trial (DCCT) units. Afinion, DCA Vantage, B-analyst, and Cobas B101 instruments passed the NGSP criteria with 2 different reagent lot numbers. Quo-Test, Quo-Lab, and InnovaStar instruments had a negative bias compared to the mean of the 3 SRMPs and failed NGSP criteria. Most of the common Hb variants did not interfere with the investigated instruments, except Hb AE for the Cobas B101.

CONCLUSIONS

Afinion, DCA Vantage, Cobas B101, and B-analyst instruments met the generally accepted performance criteria for Hb A(1c). Quo-Test, Quo-Lab, and InnovaStar met the criteria for precision but not for bias. Proficiency testing should be mandated for users of Hb A1c POC assays to ensure quality.

The relationship between estimated average glucose and fasting plasma glucose

BACKGROUND

Estimated average glucose (eAG) is a value calculated from hemoglobin A1c (HbA1c) that reflects average glycemic status over the preceding few months. A linear relationship between HbA1c and eAG was demonstrated by the International HbA1c-Derived Average Glucose (ADAG) Trial in 2008. We investigated the relationship between fasting plasma glucose (FPG) and eAG.

METHODS

This retrospective study was conducted by reviewing the medical records of 6443 subjects, including 5567 diabetic patients and 876 non-diabetic subjects. The levels of HbA1c and FPG were reviewed and eAG was calculated using the regression equation published by the ADAG trial: eAGmmol/L=1.59×HbA1c(NGSP, %)-2.59[eAGmg/dL= 28.7×HbA1c(NGSP, %)-46.7].

RESULTS

In all subjects, FPG showed a moderate correlation with eAG (r=0.672, p<0.001). When diabetic and non-diabetic subjects were divided into subgroups according to FPG level, the correlation between eAG and FPG decreased in both diabetic [FPG ≥10.0 mmol/L (180 mg/dL), r=0.425; FPG 7.2-9.9 mmol/L (130-179 mg/dL), r=0.373; FPG <7.2 mmol/L (130 mg/dL), r=0.202] and non-diabetic [FPG 5.6-6.9 mmol/L (100-125 mg/dL), r=0.363; FPG <5.6 mmol/L (100 mg/dL), r=0.186] subgroups as the FPG level decreased. The differences between eAG and FPG were statistically significant (p<0.001). Only 81% (4487/5567) of diabetic patients had a lower FPG level than eAG level.

CONCLUSIONS

Our results suggest that the relationship between eAG and FPG may depend on glycemic control, thereby enhancing our understanding of eAG.

[Assays of HbA1c and Amadori products in human biology]

Different Amadori products, formed during the early steps of the non-enzymatic glycation of proteins, may be assayed in current practice in human biology. The most important marker is HbA1c, resulting from the binding of glucose to the N-terminal extremity of HbA beta chains. HbA1c may be evaluated by various techniques (ion exchange or affinity high performance liquid chromatography, capillary electrophoresis, immunoassay, enzymatic technique) and is considered the best marker of diabetic patient survey. Due to its irreversible and cumulative formation, it provides a retrospective information on the glycemic balance over the four to eight weeks preceding blood collection. It benefits from an international standardization, based on a reference method using liquid chromatography coupled to capillary electrophoresis or mass spectrometry, maintained by an international network of reference laboratories. When HbA1c assay cannot be used (anemia, hemolysis, hemoglobinopathy) or when a shorter period of glycemic equilibrium must be evaluated (child and adolescent, pregnancy, therapeutic changes), other Amadori products may be assayed, like plasma fructosamine (all plasma glycated proteins) or glycated albumin. Nevertheless, these assays are less used in practice, because their semiological value has been less evidenced. Besides, fructosamine assay lacks specificity, and glycated albumin assay has been described recently. An expanding use of HbA1c assay is expected, especially for the diagnosis of diabetes mellitus and the evaluation of other risks, especially cardiovascular ones.

LDL cholesterol performance of beta quantification reference measurement procedure

BACKGROUND

Accurate measurement of blood lipids is crucial in cardiovascular disease risk management. The Centers for Disease Control and Prevention (CDC) Cholesterol Reference Method Laboratory Network (CRMLN) has assured the accuracy of these measurements for over 20 years using beta quantification (BQ) method as reference measurement procedure (RMP) for high- and low-density lipoprotein cholesterol (HDL-C, LDL-C). Only limited data exist about the performance of the BQ RMP.

METHODS

Bottom fraction cholesterol (BFC), HDL-C, and LDL-C results after ultracentrifugation from the CDC lipid reference laboratory and the Japanese CRMLN laboratory were compared using 280 serum samples measured over the past 15 years. Data were compared statistically using method comparison and bias estimation analysis.

RESULTS

Regression analysis between CDC (x) and Osaka (y) for BFC, HDL-C, and LDL-C were y=0.988x+1.794 (R(2)=0.997), y=0.980x+1.118 (R(2)=0.994), and y=0.987x+1.200 (R(2)=0.997), respectively. The Osaka laboratory met performance goals for 90% to 95% of the CDC reference values.

CONCLUSIONS

The BQ method by the Osaka CRMLN laboratory is highly accurate and has been stable for over 15 years. Accurate measurement of BFC is critical for the determination of LDL-C.

Comparison of Arkray/ELITech ADAMS HA-8180V with Bio-Rad Variant, II Turbo2.0 and Tosoh Bioscience HLC-723G8 for HbA1c determination

OBJECTIVE

This study aimed to evaluate a new ion-exchange HPLC system to measure hemoglobin A1c (HbA1c) in comparison to two other widely used HPLC systems.

METHODS

Analytical performance and hemoglobin variants detection was assessed on the new Arkray/ELITech ADAMS HA-8180V, in parallel to Bio-Rad Variant II Turbo2.0 and Tosoh Bioscience HLC-723G8. A method comparison and concordance for the classification of patients according to the American Diabetes Association (ADA) categories was performed using kappa test.

RESULTS

ADAMS HA-8180V demonstrated excellent within-run imprecision (0%) and between-run imprecision: ≤1.21% using blood sample and ≤0.94% using quality controls. Method comparison of ADAMS HA-8180V with the two other systems yielded very high coefficient correlation (r > 0.995). A very good agreement (kappa value ≥0.81) was observed between methods for the classification of patients according to the ADA categories. In addition, all systems were able to detect the presence of most classical variants such as HbC, HbS, HbD, and HbE.

CONCLUSION

The Arkray/ELITech ADAMS HA-8180V demonstrated high analytical performance similar to previous systems such as Biorad(TM) Variant II Turbo 2.0 and Tosoh Bioscience HLC-723G8. The three systems allow a high-quality HbA1c measurement and appeared interchangeable for diabetes diagnosis or for the therapeutic monitoring of patients without hemoglobin variants.

Statins in low doses reduce VEGF and bFGF serum levels in patients with type 2 diabetes mellitus

BACKGROUND/AIMS

Recent experimental research revealed that statins at low doses induce angiogenesis, which in turn may be related to the course of atherosclerosis. There are no clinical studies evaluating the effect of 'low-dose' statins on serum levels of angiogenesis regulators in diabetic subjects. We aimed to explain how low doses of statins modify the serum concentrations of two potent proangiogenic factors, vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF), in patients with type 2 diabetes.

METHODS

Measurements of fasting glucose level, HbA1c, 1,5-anhydro-D-glucitol and lipid profile were taken from 47 patients with type 2 diabetes treated with low doses of atorvastatin (10 mg daily) or simvastatin (10-20 mg daily), from 45 statin-free patients with type 2 diabetes and from 23 nondiabetic subjects. Measurements of VEGF and bFGF in serum were taken using the BD™ Cytometric Bead Array.

RESULTS AND CONCLUSION

Statins used in low doses in patients with type 2 diabetes reduce the serum concentration of VEGF and bFGF which suggests antiangiogenic potential of these doses. Nevertheless, this effect could be neutralized by postprandial hyperglycemia.

Entropy analysis of muscular near-infrared spectroscopy (NIRS) signals during exercise programme of type 2 diabetic patients: quantitative assessment of muscle metabolic pattern

Diabetes mellitus (DM) is a metabolic disorder that is widely rampant throughout the world population these days. The uncontrolled DM may lead to complications of eye, heart, kidney and nerves. The most common type of diabetes is the type 2 diabetes or insulin-resistant DM. Near-infrared spectroscopy (NIRS) technology is widely used in non-invasive monitoring of physiological signals. Three types of NIRS signals are used in this work: (i) variation in the oxygenated haemoglobin (O2Hb) concentration, (ii) deoxygenated haemoglobin (HHb), and (iii) ratio of oxygenated over the sum of the oxygenated and deoxygenated haemoglobin which is defined as: tissue oxygenation index (TOI) to analyze the effect of exercise on diabetes subjects. The NIRS signal has the characteristics of non-linearity and non-stationarity. Hence, the very small changes in this time series can be efficiently extracted using higher order statistics (HOS) method. Hence, in this work, we have used sample and HOS entropies to analyze these NIRS signals. These computer aided techniques will assist the clinicians to diagnose and monitor the health accurately and easily without any inter or intra observer variability. Results showed that after a one-year of physical exercise programme, all diabetic subjects increased the sample entropy of the NIRS signals, thus revealing a better muscle performance and an improved recruitment by the central nervous system. Moreover, after one year of physical therapy, diabetic subjects showed a NIRS muscular metabolic pattern that was not distinguished from that of controls. We believe that sample and bispectral entropy analysis is need when the aim is to compare the inner structure of the NIRS signals during muscle contraction, particularly when dealing with neuromuscular impairments.

HbA1c: a review of analytical and clinical aspects

After the relationship between glycemic control and the HbA1c concentration was demonstrated, many tests have been developed to determine the HbA1c concentration. The test results are standardized to the International Federation of Clinical Chemistry (IFCC) Reference Measurement Procedure (RMP) in harmony with the efforts of the National Glycohemoglobin Standardization Program (NGSP). The longitudinal use of the test requires strict quality management including accreditation of the laboratory, a dedicated internal control design, participation in an external quality assessment (EQA) program (proficiency test), and careful consideration of pre- and post-analytical aspects of the test. Performance goals for optimizing determination of the HbA1c concentration have been described. As an index of long-term glycemic control and a risk predictor, the HbA1c concentration is an indispensable part of routine management of diabetes. Because of the improving quality of the test, the HbA1c concentration is being increasingly applied in the diagnosis of diabetes. There are, however, concerns of this application in point-of-care settings. The HbA1c concentration is also used to achieve stringent control in pregnant diabetic patients. Strict standardization enables the definition of universal reference values and clinical decision limits. This review describes the present status of analytical and clinical aspects of determining the HbA1c concentration and highlights the challenges involved.

Evaluation of haemoglobin A1c measurement by an enzymatic method using an automated analyser that has an on-board haemolysis system

BACKGROUND

Enzymatic assays, which can be run on a general automated clinical analyser, have been developed for haemoglobin A1c (HbA1c) measurement. The performance of the BM Test HbA1c which is an enzymatic HbA1c assay was evaluated using the Bio Majesty (BM)6010/C, which has an on-board haemolysis system.

METHODS

We evaluated whether the difference in sampling position from the centrifuged erythrocyte layer caused a difference in HbA1c values obtained by the BM6010/C and the Tosoh G7. The performance of the BM Test HbA1c was evaluated.

RESULTS

The results of the paired t-test showed no significant difference between the values of HbA1c when the tip positions of the sample probe were at 1 mm, 3 mm or 5 mm and the values given by the Tosoh G7. The coefficient of variation (CV) of intra-assay and inter-assay precision were both approximately 1.0%. The correlation coefficient obtained from an analysis of 351 routine laboratory samples with the BM Test HbA1c and the Tosoh G7 was 0.994. The upper limit of linearity was verified up to 17.0 (NGSP%). No interference was observed from chemically modified derivatives of haemoglobin. The presence of haemoglobin variants produced no statistically significant differences in the results between the BM Test HbA1c and the Primus high-performance liquid chromatography (HPLC). Accuracy evaluation using an International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) HbA1C control was within 3.4% relative error (%) of the assigned value.

CONCLUSIONS

The above outcomes prove that the measurement system, the BM Test HbA1c analysed on the BM6010/C, which has an on-board haemolysis system, is effective in laboratory routine tests.

Evaluation of turbidimetric inhibition immunoassay (TINIA) and HPLC methods for glycated haemoglobin determination

BACKGROUND

Various factors may affect the accuracy of hemoglobin (Hb) A1c measurements that are widely used to monitor glycemic control in diabetic patients. This study was aimed to compare the values of HbA1c obtained by two different methods, Roche Tina-quant second and thirdgeneration HbA1c assays based on the turbidimetric inhibition immunoassay (TINIA), and high-performance liquid chromatography (HPLC) cation-exchange method used by Arkray Adams HA-8160 analyzer.

METHODS

Measurements of HbA1c were carried out in blood samples from 2,917 patients using above-mentioned methods. Linear regression was used for the correlation analysis and linear equations. Bland-Altman plots were performed from method comparison data using MedCalc statistical software.

RESULTS

For the low control, the second generation Tina-quant assay had within-run and between-run CVs 0.8% and 0.9%; for the high control within-run and between-run CVs were 1% and 0.96%, respectively. HPLC method for the low control had within-run CV 1% and between-run CV 1.3%; for the high control within-run CV was 0.6% and between-run CV was 0.9%.

CONCLUSION

There was a good concordance between the results of TINIA and HPLC methods (y = 1.091x - 0.363; r(2) = 0.96).

Development of affinity microcolumns for drug-protein binding studies in personalized medicine: interactions of sulfonylurea drugs with in vivo glycated human serum albumin

This report used high-performance affinity microcolumns to examine the changes in binding by sulfonylurea drugs to in vivo glycated HSA that had been isolated from individual patients with diabetes. An immunoextraction approach was developed to isolate HSA and glycated HSA from clinical samples, using only 20 μL of plasma or serum and 6-12 nmol of protein to prepare each affinity microcolumn. It was found that the affinity microcolumns could be used in either frontal analysis or zonal elution studies, which typically required only 4-8 min per run. The microcolumns had good stability and allowed data to be obtained for multiple drugs and experimental conditions over hundreds of sample application cycles. Both the overall binding, as measured by frontal analysis, and site-specific interactions, as examined by zonal elution, showed good agreement with previous data that had been obtained for in vitro glycated HSA with similar levels of modification. It was also possible to directly compare the changes in site-specific binding that occurred between sulfonylurea drugs or as the level of HSA glycation was varied. This method is not limited to clinical samples of glycated HSA but could be adapted for work with other modified proteins of interest in personalized medicine.

Predisposing factors for surgical site infection of spinal instrumentation surgery for diabetes patients

PURPOSE

Diabetes mellitus (DM) is known as an important risk factor for surgical site infection (SSI) in spine surgery. It is still unclear however which DM-related parameters have stronger influence on SSI. The purpose of this study is to determine predisposing factors for SSI following spinal instrumentation surgery for patients with DM.

METHODS

110 DM patients (66 males and 44 females) who underwent spinal instrumentation surgery in one institute were enrolled in this study. For each patient, various preoperative or intraoperative parameters were reviewed from medical records. Patients were divided into two groups (SSI or non-SSI) based on the postoperative course. Each parameter between these two groups was compared. Univariate and multivariate analyses were performed to determine predisposing factor for SSI.

RESULTS

The SSI group consisted of 11 patients (10%), and the non-SSI group of 99 patients (90%). Univariate analysis revealed that preoperative proteinuria (p = 0.01), operation time (p = 0.04) and estimated blood loss (p = 0.02) were significantly higher in the SSI group compared to the non-SSI group. Multivariate logistic regression identified preoperative proteinuria as a statistically significant predictor of SSI (OR 6.28, 95% CI 1.58-25.0, p = 0.009).

CONCLUSIONS

Proteinuria is a significant predisposing factor for SSI in spinal instrumentation surgery for DM patients. DM patients with proteinuria who are likely to suffer latent nephropathy have a potential risk for SSI. For them less invasive surgery is recommended for spinal instrumentation. In this retrospective study, there was no significant difference of preoperative condition in glycemic control between the two groups.

Haemoglobin A1c: Historical overview and current concepts

Since the discovery of the relation between increased concentrations of fast haemoglobin fractions in patients with diabetes mellitus compared to concentrations in subjects without diabetes mellitus by Samuel Rahbar and co-workers in 1969, glycated haemoglobin A1c (HbA1c) has become a "gold standard" for glucose management in patients with diabetes mellitus. Recently, HbA1c has been advocated as a diagnostic marker for diabetes mellitus, which further underlines the importance of HbA1c. There are currently more than 30 methods available on the market with an analytical performance ranging from poor to state of the art. This review describes the biochemistry of HbA1c and the concepts of analytical and biological variation with respect to the measurement of HbA1c. Subsequently, aspects regarding the discovery of HbA1c are described. In addition, an overview is given on the assays methods that are currently available for the measurement of HbA1c. Finally, recommendations for the minimally required analytical performance characteristics of the current HbA1c assays are presented.

The long and winding road to optimal HbA1c measurement

The importance of hemoglobin A1c (HbA1c) as an indicator of mean glycemia and risks for complications in patients with diabetes mellitus was established by the results of long-term clinical trials, most notably the Diabetes Control and Complications Trial (DCCT) and United Kingdom Prospective Diabetes Study (UKPDS), published in 1993 and 1998 respectively. However, clinical application of recommended HbA1c targets that were based on these studies was difficult due to lack of comparability of HbA1c results among assay methods and laboratories. Thus, the National Glycohemoglobin Standardization Program (NGSP) was initiated in 1996 with the goal of standardizing HbA1c results to those of the DCCT/UKPDS. HbA1c standardization efforts have been highly successful; however, a number of issues have emerged on the "long and winding road" to better HbA1c, including the development of a higher-order HbA1c reference method by the International Federation of Clinical Chemistry (IFCC), recommendations to use HbA1c to diagnose as well as monitor diabetes, and point-of-care (POC) HbA1c testing. Here, we review the past, present and future of HbA1c standardization and describe the current status of HbA1c testing, including limitations that healthcare providers need to be aware of when interpreting HbA1c results.

A semi-mechanistic model of the relationship between average glucose and HbA1c in healthy and diabetic subjects

HbA1c is the most commonly used biomarker for the adequacy of glycemic management in diabetic patients and a surrogate endpoint for anti-diabetic drug approval. In spite of an empirical description for the relationship between average glucose (AG) and HbA1c concentrations, obtained from the A1c-derived average glucose (ADAG) study by Nathan et al., a model for the non-steady-state relationship is still lacking. Using data from the ADAG study, we here develop such models that utilize literature information on (patho)physiological processes and assay characteristics. The model incorporates the red blood cell (RBC) aging description, and uses prior values of the glycosylation rate constant (KG), mean RBC life-span (LS) and mean RBC precursor LS obtained from the literature. Different hypothesis were tested to explain the observed non-proportional relationship between AG and HbA1c. Both an inverse dependence of LS on AG and a non-specificity of the National Glycohemoglobin Standardization Program assay used could well describe the data. Both explanations have mechanistic support and could be incorporated, alone or in combination, in models allowing prediction of the time-course of HbA1c changes associated with changes in AG from, for example dietary or therapeutic interventions, and vice versa, to infer changes in AG from observed changes in HbA1c. The selection between the alternative mechanistic models require gathering of new information.

Reference measurement procedures for Alzheimer's disease cerebrospinal fluid biomarkers: definitions and approaches with focus on amyloid β42

Cerebrospinal fluid (CSF) biomarkers for Alzheimer's disease (AD) are increasingly used in clinical settings, research and drug trials. However, their broad-scale use on different technology platforms is hampered by the lack of standardization at the level of sample handling, determination of concentrations of analytes and the absence of well-defined performance criteria for in vitro diagnostic or companion diagnostic assays, which influences the apparent concentration of the analytes measured and the subsequent interpretation of the data. There is a need for harmonization of CSF AD biomarker assays that can reliably, across centers, quantitate CSF biomarkers with high analytical precision, selectivity and stability over long time periods. In this position paper, we discuss reference procedures for the measurement of CSF AD biomarkers, especially amyloid β42 and tau. We describe possible technical approaches, focusing on a selected reaction monitoring mass spectrometry assay as a candidate reference method for quantification of CSF amyloid β42.

High-resolution HbA(1c) separation and hemoglobinopathy detection with capillary electrophoresis

The CAPILLARYS HbA(1c) kit used on the CAPILLARYS 2 Flex Piercing system is designed for separating and quantifying the HbA(1c) fraction of hemoglobin while detecting hemoglobin variants and HbA(2). The aim of this study was to assess the performance of this new capillary electrophoresis kit for routine HbA(1c) quantification for patients with diabetes. The reliability of the system for HbA(2) measurement was also assessed. Precision, correlation, and linearity studies were performed. The effect of hemoglobin concentration and the presence of coexistent interfering substances were evaluated. The results were found to be accurate and linear in the clinically significant analytic range with excellent precision (mean interassay coefficient of variation of 0.7%). HbA(1c) measurement is independent of the presence of common hemoglobin interferences for HbA(1c) quantification and the total concentration of hemoglobin. Moreover, the technique provides a rapid and reliable separation of HbA(2). The measurement is reproducible and the results in β-thalassemia carriers were statistically different from those in noncarriers. Thus, this technique might be used for β-thalassemia detection. Given the short time of the analysis and the high throughput, this is a suitable system for the control of diabetes and the detection of hemoglobinopathies in laboratories with high workflow.

The association between left ventricular diastolic function and a mild-to-moderate decrease in glomerular filtration rate in patients with type 2 diabetes mellitus

This prospective study evaluated the relationship between echocardiography parameters of left ventricular (LV) diastolic function and mild-to-moderate renal function impairment in 82 patients with type 2 diabetes mellitus. The mean age of the patients was 61.1 years. A significant correlation was found between estimated glomerular filtration rate (eGFR) and the ratio of peak velocity of early transmitral flow (E) to peak velocity of early diastolic mitral annular motion (E'). Cluster analysis revealed two subgroups of patients with different E' values but comparable eGFRs. The correlation between eGFR and E/E' was significant in 38 patients with E' ≤ 7.1 cm/s, but not significant in 44 patients with E' > 7.1 cm/s. The results suggest that the deterioration of LV relaxation (E') represents the underlying condition for the association between mild-to-moderate renal function impairment and the non-invasive parameter of LV end-diastolic pressure (E/E'), in patients with type 2 diabetes without any previous cardiovascular event and with well-controlled blood pressure.

Hemoglobin A1c above threshold level is associated with decreased β-cell function in overweight Latino youth

OBJECTIVE

To examine whether a hemoglobin A1c (HbA1c)-identified prediabetic state (HbA1c ≥ 6.0%-6.4%) is associated with decreased insulin sensitivity (SI) and β-cell dysfunction, known factors in the pathogenesis of type 2 diabetes, in an overweight pediatric population.

STUDY DESIGN

A total of 206 healthy overweight Latino adolescents (124 males and 82 females; mean age, 13.1 ± 2.0 years) were divided into 2 groups: lower risk (n=179), with HbA1c <6.0%, and higher risk (n=27), with HbA1c 6.0%-6.4%. Measurements included HbA1c, oral glucose tolerance testing, fasting and 2-hour glucose and insulin, SI, acute insulin response, and disposition index (an index of β-cell function) by the frequently sampled intravenous glucose tolerance test with minimal modeling. Body fat was determined by dual-energy X-ray absorptiometry.

RESULTS

Compared with the lower risk group, the higher risk group had 21% lower SI (1.21 ± 0.06 vs 1.54 ± 0.13; P<.05), 30% lower acute insulin response (928 ± 102 vs 1342 ± 56; P<.01), and a 31% lower disposition index (1390 ± 146 vs 2023 ± 83; P=.001) after adjusting for age and total percent body fat.

CONCLUSION

These data provide clear evidence of greater impairment of β-cell function in overweight Latino children with HbA1c 6.0%-6.4%, and thereby support the adoption of the International Expert Committee's HbA1c-determined definition of high-risk state for overweight children at risk for type 2 diabetes.

Current controversies in the use of haemoglobin A1c

Haemoglobin A(1c) (HbA(1c)) has recently been adopted by the World Health Organization into its recommended criteria for diabetes diagnosis. Much debate continues regarding the relative benefits and potential disadvantages surrounding the use of HbA(1c) for this purpose. There is a lack of consensus as to whether this alteration to the definition of diabetes is a step forward or whether it could add further confusion and ambiguity to the debate on the method and criteria for the diagnosis of this globally important disease. This review provides a comprehensive overview of the current issues surrounding how HbA(1c) is measured and reported; and of the evidence for and against its use in diagnosis.

Design, history and results of the Thiazolidinedione Intervention with vitamin D Evaluation (TIDE) randomised controlled trial

AIMS/OBJECTIVE

Conflicting data regarding cardiovascular effects of thiazolidinediones (TZDs) and extra-skeletal effects of vitamin D supported the need for a definitive trial. The Thiazolidinedione Intervention with vitamin D Evaluation (TIDE) trial aimed to assess the effects of TZDs (rosiglitazone and pioglitazone) on cardiovascular outcomes and the effects of vitamin D (cholecalciferol) on cancers and mortality.

METHODS

A large multicentre 3 × 2 factorial double-blind placebo-controlled randomised trial recruited from outpatient primary care and specialty clinics in 33 countries. From June 2009 to July 2010, 1,332 people with type 2 diabetes and other cardiovascular risk factors aged ≥ 50 years whose HbA(1c) was 6.5-9.5% (48-80 mmol/mol) when using two or fewer glucose-lowering drugs were randomised by a central computer system to placebo (n = 541), rosiglitazone 4-8 mg/day (n = 399) or pioglitazone 30-45 mg/day (n = 392); 1,221 participants were randomised to placebo (n = 614) or vitamin D 1,000 IU/day (n = 607). Participants and all study personnel were blind to treatment allocation. The primary outcome for the TZD arm was the composite of myocardial infarction, stroke or cardiovascular death, and for the vitamin D arm it was cancer or all-cause death. All randomised participants were included in the primary analysis.

RESULTS

From the study design, 16,000 people were to be followed for approximately 5.5 years. However, the trial was stopped prematurely because of regulatory concerns after a mean of 162 days without consideration of the accrued data. In the TZD arm, the cardiovascular outcome occurred in five participants (0.9%) in the placebo groups and three participants (0.4%) in the TZD groups (two allocated to pioglitazone, one to rosiglitazone). In the vitamin D arm, the primary outcome occurred in three participants (0.5%) in the placebo group and in two participants (0.3%) receiving vitamin D. Adverse events were comparable in all groups.

CONCLUSIONS/INTERPRETATION

Uncertainty persists regarding the clinically relevant risks and benefits of TZDs and vitamin D because of the early cancellation of this comprehensive trial.

Is there a relationship between mean blood glucose and glycated hemoglobin?

Measurement of hemoglobin A1c (HbA1c) is considered the gold standard for monitoring chronic glycemia of diabetes patients. Hemoglobin A1c indicates an average of blood glucose levels over the past 3 months. Its close association with the risk for the development of long-term complications is well established. However, HbA1c does not inform patients about blood glucose values on a daily basis; therefore, frequent measurements of blood glucose levels are necessary for the day-to-day management of diabetes. Clinicians understand what HbA1c means and how it relates to glucose, but this is not the case with patients. Therefore, the translation of the HbA1c results into something more familiar to patients seemed a necessity. The scope of this article is to review the literature to search for enough scientific evidence to support the idea of a close relationship between HbA1c and mean blood glucose (MBG), and to justify the translation of HbA1c into something that reflects the MBG. Most studies confirm a close relationship between HbA1c and MBG, although different studies result in different linear equations. Factors affecting this relationship may limit the usefulness and applicability of a unique mathematical equation to all diabetes populations.