HbA1c measurement

Electrochemical Biosensors for Whole Blood Analysis: Recent Progress, Challenges, and Future Perspectives

Whole blood, as one of the most significant biological fluids, provides critical information for health management and disease monitoring. Over the past 10 years, advances in nanotechnology, microfluidics, and biomarker research have spurred the development of powerful miniaturized diagnostic systems for whole blood testing toward the goal of disease monitoring and treatment. Among the techniques employed for whole-blood diagnostics, electrochemical biosensors, as known to be rapid, sensitive, capable of miniaturization, reagentless and washing free, become a class of emerging technology to achieve the target detection specifically and directly in complex media, e.g., whole blood or even in the living body. Here we are aiming to provide a comprehensive review to summarize advances over the past decade in the development of electrochemical sensors for whole blood analysis. Further, we address the remaining challenges and opportunities to integrate electrochemical sensing platforms.

There is no dose-response relationship between the amount of exercise and improvement in HbA1c in interventions over 12 weeks in patients with type 2 diabetes: a meta-analysis and meta-regression

AIMS

Aerobic exercise is well recognised as an effective treatment for people with type 2 diabetes but the optimal amount of aerobic exercise to improve glycaemic control remains to be determined. Thus, the aim of this meta-analysis and meta-regression was to assess the impact of volume and intensity of aerobic exercise on glycaemic control.

METHODS

Medline, Cochrane, Embase, and Web of Science databases were searched up until 15 December 2020 for the terms "aerobic exercise AND glycaemic control", "type 2 diabetes AND exercise", and "exercise AND glycaemic control AND Type 2 diabetes AND randomised control trial". We included (i) randomised control trials of ≥ 12 weeks, (ii) trials where participants had type 2 diabetes and were aged 18 or over, and (iii) the trial reported HbA1c concentrations pre- and post-intervention. Two reviewers selected studies and extracted data. Data are reported as standardised mean difference (SMD) and publication bias was assessed using funnel plots.

RESULTS

A total of 5364 original titles were identified. Sixteen studies were included in the meta-analysis. Aerobic exercise reduced HbA1c versus control (SMD = 0.56 (95% CI 0.3-0.82), p < 0.001). There were also significant reductions in BMI (SMD = 0.76 (95% CI 0.25-1.27), p < 0.05). There was no dose-response relationship between improvement in HbA1c and the intensity and volume of the intervention (p > 0.05).

CONCLUSIONS

Twelve-week or longer aerobic exercise programmes improve glycaemic control and BMI in adults with type 2 diabetes. Longer or more intense interventions appear to confer no additional benefit on HbA1c.

Achieving the HbA1c Target Requires Longer Time in Range in Pregnant Women With Type 1 Diabetes

CONTEXT

Continuous glucose monitoring (CGM) overcomes the limitations of glycated hemoglobin (HbA1c).

OBJECTIVE

This study aimed to investigate the relationship between CGM metrics and laboratory HbA1c in pregnant women with type 1 diabetes.

METHODS

An observational study enrolled pregnant women with type 1 diabetes who wore CGM devices during pregnancy and postpartum from 11 hospitals in China from January 2015 to June 2019. CGM data were collected to calculate time in range (TIR), time above range (TAR), time below range (TBR), and glycemic variability parameters. Relationships between the CGM metrics and HbA1c were explored. Linear and curvilinear regressions were conducted to investigate the best-fitting model to clarify the influence of HbA1c on the TIR-HbA1c relationship during pregnancy.

RESULTS

A total of 272 CGM data and corresponding HbA1c from 98 pregnant women with type 1 diabetes and their clinical characteristics were analyzed in this study. Mean HbA1c and TIR were 6.49 ± 1.29% and 76.16 ± 17.97% during pregnancy, respectively. HbA1c was moderately correlated with TIR3.5-7.8(R = -0.429, P = .001), mean glucose (R = 0.405, P = .001) and TAR7.8 (R = 0.435, P = .001), but was weakly correlated with TBR3.5 (R = 0.034, P = .001) during pregnancy. On average, a 1% (11 mmol/mol) decrease in HbA1c corresponded to an 8.5% increase in TIR3.5-7.8. During pregnancy, HbA1c of 6.0%, 6.5%, and 7.0% were equivalent to a TIR3.5-7.8 of 78%, 74%, and 69%, respectively.

CONCLUSION

We found there was a moderate correlation between HbA1c and TIR3.5-7.8 during pregnancy. To achieve the HbA1c target of less than 6.0%, pregnant women with type 1 diabetes should strive for a TIR3.5-7.8 of greater than 78% (18 hours 43 minutes) during pregnancy.

Continuous glucose monitoring targets in type 1 diabetes pregnancy: every 5% time in range matters

With randomised trial data confirming that continuous glucose monitoring (CGM) is associated with improvements in maternal glucose control and neonatal health outcomes, CGM is increasingly used in antenatal care. Across pregnancy, the ambition is to increase the CGM time in range (TIR), while reducing time above range (TAR), time below range (TBR) and glycaemic variability measures. Pregnant women with type 1 diabetes currently spend, on average, 50% (12 h), 55% (13 h) and 60% (14 h) in the target range of 3.5-7.8 mmol/l (63-140 mg/dl) during the first, second and third trimesters, respectively. Hyperglycaemia, as measured by TAR, reduces from 40% (10 h) to 33% (8 h) during the first to third trimester. A TIR of >70% (16 h, 48 min) and a TAR of <25% (6 h) is achieved only in the final weeks of pregnancy. CGM TBR data are particularly sensor dependent, but regardless of the threshold used for individual patients, spending ≥4% of time (1 h) below 3.5 mmol/l or ≥1% of time (15 min) below 3.0 mmol/l is not recommended. While maternal hyperglycaemia is a well-established risk factor for obstetric and neonatal complications, CGM-based risk factors are emerging. A 5% lower TIR and 5% higher TAR during the second and third trimesters is associated with increased risk of large for gestational age infants, neonatal hypoglycaemia and neonatal intensive care unit admissions. For optimal neonatal outcomes, women and clinicians should aim for a TIR of >70% (16 h, 48 min) and a TAR of <25% (6 h), from as early as possible during pregnancy.

Single-Use Disposable Electrochemical Label-Free Immunosensor for Detection of Glycated Hemoglobin (HbA1c) Using Differential Pulse Voltammetry (DPV)

A single-use disposable in vitro electrochemical immunosensor for the detection of HbA1c in undiluted human serum using differential pulse voltammetry (DPV) was developed. A three-electrode configuration electrochemical biosensor consisted of 10-nm-thin gold film working and counter electrodes and a thick-film printed Ag/AgCl reference electrode was fabricated on a polyethylene terephthalate (PET) substrate. Micro-fabrication techniques including sputtering vapor deposition and thick-film printing were used to fabricate the biosensor. This was a roll-to-roll cost-effective manufacturing process making the single-use disposable in vitro HbA1c biosensor a reality. Self-assembled monolayers of 3-Mercaptopropionic acid (MPA) were employed to covalently immobilize anti-HbA1c on the surface of gold electrodes. Electrochemical impedance spectroscopy (EIS) and X-ray photoelectron spectroscopy (XPS) confirmed the excellent coverage of MPA-SAM and the upward orientation of carboxylic groups. The hindering effect of HbA1c on the ferricyanide/ferrocyanide electron transfer reaction was exploited as the HbA1c detection mechanism. The biosensor showed a linear range of 7.5–20 µg/mL of HbA1c in 0.1 M PBS. Using undiluted human serum as the test medium, the biosensor presented an excellent linear behavior (R² = 0.999) in the range of 0.1–0.25 mg/mL of HbA1c. The potential application of this biosensor for in vitro measurement of HbA1c for diabetic management was demonstrated.

Morphologic and cytomorphometric analysis of exfoliated buccal mucosal cells in diabetes patients

BACKGROUND

It is now known that the disease process of diabetes has effects on various tissues of the body. The following study was done to analyze the effects of diabetes on oral tissues.

AIMS

To study the morphology and cytomorphometry of the cells obtained in cytologic smears from the buccal mucosa of diabetic patients.

MATERIALS AND METHODS

Smears were obtained from clinically normal buccal mucosa of 50 randomly selected diabetic patients attending the diabetic clinic and the out-patient department and of five healthy subjects as control. Smears were stained using Papanicolaou method, and using a micrometer mean values of nuclear diameter (ND), cell diameter (CD), cytoplasmic diameter (CyD) and nucleus: cytoplasm ratio (N: C ratio) were obtained for each patient. Diabetic patients were divided into four groups based on the glycosylated hemoglobin (GHb) values for comparison.

STATISTICAL ANALYSIS USED

Student's T-test and Fisher's F-test.

RESULTS

Statistically significant increase in ND (P=0.0367) was found in diabetic patients compared to controls. Degree of glycemic control significantly affected ND (P=0.0042) and N: C ratio (P=0.0055). In general, as the severity of diabetes increases, ND and N: C ratio rise gradually.

CONCLUSIONS

Diabetes produces definite morphologic and cytomorphometric changes in the buccal mucosa of patients. However, further research in this direction is indicated, to analyze the significance of these findings as a tool for diabetes detection, as well as to obtain deeper insights into its effects on various tissues.

Does A1c consistently reflect mean plasma glucose?

BACKGROUND

A1c, a surrogate measure of glycemic control, is known to have a strong linear correlation with mean plasma glucose (MPG) when analyzed in populations of patients. However, clinically significant intersubject variability in this relationship exists, which suggests that A1c measurements may not reflect actual glycemic control in some patients. In the present study we explored the extent to which A1c accurately represents glycemic control, as measured by MPG, for individual patients.

METHODS

Data were pooled from randomized clinical trials in which A1c and self-monitored plasma glucose (SMPG) profiles were collected by patients with Type 2 diabetes treated with insulin analog regimens. MPG levels were calculated from SMPG profiles. Distributions of MPG were analyzed for patients within similar ranges of A1c (<6.5%, 6.5%-<7.5%, 7.5%-<8.5%, 8.5%-<9.5%, and ≥9.5%) and distributions of A1c were analyzed in patients within similar ranges of MPG (<6.1, 6.1-<7.8, 7.8-<9.4, 9.4-<11.1, and ≥11.1 mmol/L).

RESULTS

Substantial proportions of patients had clinically significant differences between A1c and MPG. For example, among 260 patients with A1c between 6.5% and 7.5%, 10% had MPG levels <6.4 mmol/L, whereas 10% had MPG >9.5 mmol/L. Among the 224 patients with MPG levels ≥6.1 mmol/L and <7.8 mmol/L, 10% had A1c <6% and 10% had A1c >8.1%.

CONCLUSIONS

In the absence of SMPG, A1c may inadequately represent glycemic control for many diabetic patients.

Clinical impact of variability in HbA1c as assessed by simultaneously measuring fructosamine and use of error grid analysis

BACKGROUND

Haemoglobin A1c (HbA1c) is the only measure of glycaemic control used for many patients with diabetes, but it has limitations and might sometimes be misleading. HbA(1c) concentrations are influenced by conditions that alter red-cell life and there is evidence that biochemical variation in intracellular glycation rates also influence HbA1c concentrations. This paper is the first to propose a method of using simultaneously measured HbA1c and fructosamine, and error grid analysis, in the clinical setting, to gain a better understanding of glycaemic control.

METHODS

Cross-sectional analytical study using HbA1c and fructosamine measures on the same blood sample from 1744 patients having blood taken for hospital diabetes clinic appointments. No other selection or exclusion criteria were applied.

RESULTS

The fructosamine results were converted to a HbA1c equivalent which was then compared with the HbA1c. In an Altman-Bland plot, the paired result differences ranged between -6.9% and +5.5% HbA1c with 1139 (65%), 438 (25%), 130 (8%) and 37 (2%) being < or =1%, 1-2%, 2-3% or >3% of HbA1c difference, respectively. In clinical error grid analysis, 864 (50%) results had tight concordance for clinical interpretation, 761 (43%) had one block disunity of probably little clinical significance, but 105 (6%) were two blocks and 14 (1%) were three blocks discordant.

CONCLUSION

HbA1c may not accurately reflect glucose control. Our method, utilizing co-assessment with serum fructosamine, evaluates the possible clinical impact of this. We suggest the analysis used in this paper should be used routinely in diabetes practice.

The proposed terminology 'A(1c)-derived average glucose' is inherently imprecise and should not be adopted

The proposed use of a more precise standard for glycated (A(1c)) and non-glycated haemoglobin would lead to an A(1c) value, when expressed as a percentage, that is lower than that currently in use. One approach advocated to address the potential confusion that would ensue is to replace 'HbA(1c)' with a new term, 'A(1c)-derived average glucose.' We review evidence from several sources suggesting that A(1c) is, in fact, inherently imprecise as a measure of average glucose, so that the proposed terminology should not be adopted.

Different DCCT-aligned HbA1c methods and the GMS contract

BACKGROUND

Previously, different analytical methods could be compared on statistical and clinical grounds. Since 2003, the UK Departments of Health and general practitioners agreed a new primary care contract. This contract utilises clinical targets resulting in a third way to compare analytical methods.

METHODS

We compared two DCCT-aligned HbA1c analysers (Variant II analyser and a Tosoh G7) using 161 randomly selected patient specimens to see if different methods could lead to a difference in the classification for glycaemic control.

RESULTS

Ninety-seven (60.2%) and 109 (67.7%) patient specimens had a HbA1c <or= 7.4% with the Variant II analyser and Tosoh G7 respectively, that is, the two methods differed according to the DM6 GMS target by 12 patients or 7.5% of the total number of patients in the study. When McNemar's test was performed, the difference between the two methods was statistically significant with p<0.00083.

CONCLUSIONS

The National Glycohemoglobin Standardisation Programme has used clinical limits to set standards for HbA1c based on a clinical recommendation from the American Diabetes Association and has resulted in improved generalisability of results. The difference found in this study would not have affected payment under the current GMS contract. However, if the maximum threshold for payment was increased from 50% and/or the HbA1c target was decreased from 7.4%, then payment may be affected. It is important that policy makers and healthcare professionals appreciate the limitations of DCCT alignment for HbA1c methods.

Implications of different DCCT-aligned HbA1c methods on GMS clinical indicators

BACKGROUND

In 2003, a new General Medical Services (GMS) contract was agreed between UK general practitioners and the Department of Health. The three diabetes codes DM5-DM7 require glycated haemoglobin (HbA(1c)) testing and comprise 30 points in total, with 27 points being related to target glycaemic control. We compared two routinely used Diabetes Control and Complications Trial (DCCT)-aligned HbA(1c) methods to determine if different HbA(1c) methods could lead to postcode treatment to target across the UK.

METHODS

A total of 164 specimens were randomly selected from diabetic patients attending the Diabetes Centre at the Ipswich Hospital. Samples were analysed on both a DCA 2000+ Analyser and a Variant II analyser.

RESULTS

Despite a mean difference of only 6.5% between the two methods, 32 (19.5%) and 63 (38.4%) patient samples had an HbA(1c) < or = 7.4% with the Variant II analyser and DCA 2000+ Analyser, respectively. Thus, the two methods differed according to the DM6 GMS target by 31 patients, or 18.9% of the total number of patients in this study. The difference between the two methods was statistically significant with P < 10(-09) (McNemar's test).

CONCLUSIONS

DCCT-alignment has improved the transferability of HbA(1c) values; however, it is not perfect. It is important that the limitations of current DCCT-aligned HbA(1c) methods are understood by health-care professionals and policy makers, as these may have important financial and clinical implications.

Glycated haemoglobin (HbA1c) monitoring

Glycation of haemoglobin to produce HbA_1c occurs throughout the 120 day average lifespan of the red blood cell. Repeat testing in less than 120 days or situations that shorten this lifespan will produce HbA_1c results that do not fully reflect current diabetic control

Best practice in primary care pathology: review 3

This best practice review examines four series of common primary care questions in laboratory medicine: (i) "minor" blood platelet count and haemoglobin abnormalities; (ii) diagnosis and monitoring of anaemia caused by iron deficiency; (iii) secondary hyperlipidaemia and hypertriglyceridaemia; and (iv) glycated haemoglobin and microalbumin use in diabetes. The review is presented in question-answer format, referenced for each question series. The recommendations represent a précis of guidance found using a standardised literature search of national and international guidance notes, consensus statements, health policy documents and evidence-based medicine reviews, supplemented by Medline Embase searches to identify relevant primary research documents. They are not standards, but form a guide to be set in the clinical context. Most of the recommendations are based on consensus rather than evidence. They will be updated periodically to take account of new information.

HbA1c: A comparison of NGSP with IFCC transformed values

BACKGROUND

An approved IFCC reference method for measuring HbA1c, with a firm and reproducible correlation with NGSP values, is now available. We established (i) the degree of agreement of HbA1c results between the NGSP-certified and the IFCC-calibrated (converted to NGSP values) immunochemical method and (ii) the difference in the classification of control of diabetes mellitus (DM) in individual patients between the methods.

METHODS

HbA1c was measured on the same hemolysate from each patient by both methods (n=92). Results were analyzed by the kappa statistic, linear regression, and McNemar's chi(2) test.

RESULTS

Both methods achieved acceptable analytical performance. The kappa statistic measure of agreement was 0.65 and r(2)=0.937. Overall, 21 (22.8%) patients were classified differently in the extent of diabetes control (good, acceptable, or poor), with a significant difference between the 2 methods (p<0.0005).

CONCLUSIONS

The IFCC converted to NGSP values were significantly different from the previously used NGSP-certified method. The differences between the 2 methods are of sufficient magnitude that HbA1c results from these methods are not interchangeable. The IFCC method being scientifically superior in concept and design should replace the NGSP method. New HbA1c targets for DM management need to be established for the IFCC method.