Glycated hemoglobin (HbA1c) measurement in frozen whole blood depends on baseline values of fresh samples

Stability of glycated haemoglobin (HbA1c) measurements from whole blood samples kept at -196°C for seven to eight years in The Malaysian Cohort study

OBJECTIVE

Glycated haemoglobin (HbA1c) is a standard indication for screening type 2 diabetes that also has been widely used in large-scale epidemiological studies. However, its long-term quality (in terms of reproducibility) stored in liquid nitrogen is still unknown. This study is aimed to evaluate the stability and reproducibility of HbA1c measurements from frozen whole blood samples kept at -196°C for more than 7 years.

METHODS

A total of 401 whole blood samples with a fresh HbA1c measurement were randomly selected from The Malaysian Cohort's (TMC) biobank. The HbA1c measurements of fresh and frozen (stored for 7-8 years) samples were assayed using different high-performance liquid chromatography (HPLC) systems. The HbA1c values of the fresh samples were then calculated and corrected according to the later system. The reproducibility of HbA1c measurements between calculated-fresh and frozen samples was assessed using a Passing-Bablok linear regression model. The Bland-Altman plot was then used to evaluate the concordance of HbA1c values.

RESULTS

The different HPLC systems highly correlated (r = 0.99) and agreed (ICC = 0.96) with each other. Furthermore, the HbA1c measurements for frozen samples strongly correlate with the corrected HbA1c values of the fresh samples (r = 0.875) with a mean difference of -0.02 (SD: -0.38 to 0.38). Although the mean difference is small, discrepancies were observed within the diabetic and non-diabetic samples.

CONCLUSION

These data demonstrate that the HbA1c measurements between fresh and frozen samples are highly correlated and reproducible.

The influence of sample freezing at - 80 °C for 2-12 weeks on glycated haemoglobin (HbA1c) concentration assayed by HPLC method on Bio-Rad D-10® auto analyzer

INTRODUCTION

The aim of the study was to evaluate the effect of a single freeze/thaw cycle on HbA1c concentrations measured by commercially available HPLC method.

MATERIALS AND METHODS

Study included 128 whole blood samples collected from diabetic patients (N = 60) and healthy volunteers (N = 68). HbA1c concentrations were measured in fresh blood samples. Then samples were frozen at - 80 °C for up to 12 weeks. HbA1c was assayed by ion-exchange HPLC method on Bio-Rad D-10® analyzer. Variables were compared using Wilcoxon and ANOVA Kruskal-Wallis tests. Bias between HbA1c measured in fresh and frozen samples was calculated. The comparability of HbA1c concentrations was assessed by Bland-Altman plot.

RESULTS

Median (IQR) HbA1c concentration was 45.3 (36.6-61.2) mmol/mol for fresh and 45.3 (36.6-60.6) mmol/mol for frozen/thawed samples. No significant difference in HbA1c concentrations was found comparing fresh and frozen/thawed samples (P = 0.070) in the whole group, as well as in healthy and diabetic subjects. The median calculated bias between fresh and frozen/thawed samples was 0% in whole group and healthy subjects, and 1.19% in diabetic patients. No significant difference was found between the biases according to baseline HbA1c values (P = 0.150). The Bland-Altman plot analysis showed a positive bias of 0.4% (95% CI: - 2.8 - 3.7%), which indicates high compliance between HbA1c values and no relevant influence of sample freezing on clinical significance of HbA1c measurement.

CONCLUSIONS

Storage for up to 12 weeks at - 80 °C with a single freeze/thaw cycle does not affect HbA1c concentrations measured with HPLC method on Bio-Rad D-10® analyzer.

Probit Models to Investigate Prevalence of Total Diagnosed and Undiagnosed Diabetes among Aged 45 Years or Older Adults in China

The aims of this study are to identify the most important predictors of total diagnosed and undiagnosed diabetes and estimate the mean change in the predicted probability among aged 45+ adults in China. We used baseline data collected from 2011 wave of the China Health and Retirement Longitudinal Study (CHARLS) (n = 9,513). First, we estimated the prevalence of diagnosed, measured, total diagnosed, and undiagnosed diabetes. Second, we used probit models to determine whether individual attributes, socioeconomic characteristics and behavioral health factors, including smoking, alcohol consumption, obesity, central obesity, are associated with total diagnosed and undiagnosed diabetes. We also consider other factors, including contact with medical system, hypertension and urban/rural settings. Third, we estimated average marginal effects of variables in probit models. Among Chinese people aged 45+, the prevalence of diagnosed, measured, total diagnosed and undiagnosed diabetes were 5.8% (95%CI, 5.3%-6.3%), 14.7% (95%CI, 14.0%-15.4%), 17.0% (95%CI, 16.3%-17.7%), 11.3% (95%CI, 10.6%-12.0%), respectively. The probability of total diagnosed diabetes is 3.3% (95% CI, 1.2%-5.3%) and 10.2% (95% CI, 7.0%-13.5%) higher for overweight and obesity than normal BMI, 5.0% (95% CI, 3.0%-7.1%) higher for central obesity than normal waist circumference, 5.4% (95% CI, 3.7%-7.0%) higher for hypertensive than normotensive and 1.8% (95% CI, 0.8%- 2.7%) higher in urban areas than in rural areas, respectively. The probability of undiagnosed diabetes is 2.7% (95% CI, 1.2%-4.2%) and 7.2% (95% CI, 4.7%-9.6%) higher for overweight and obesity than normal BMI, 2.6% (95% CI, 0.9%-4.4%) higher for central obesity than normal waist circumference and 2.6% (95% CI, 1.2%-4.0%) higher for hypertensive than normotensive, respectively, and -1.5% (95% CI, -2.5% to -0.5%) lower for individuals who were in contact with the medical system. Greater focus on prevention of diabetes is necessary for obesity, central obesity, hypertensive and in urban areas for middle-aged and older in China.

Contrasting Effects of Lixisenatide and Liraglutide on Postprandial Glycemic Control, Gastric Emptying, and Safety Parameters in Patients With Type 2 Diabetes on Optimized Insulin Glargine With or Without Metformin: A Randomized, Open-Label Trial

OBJECTIVE

This mechanistic trial compared the pharmacodynamics and safety of lixisenatide and liraglutide in combination with optimized insulin glargine with/without metformin in type 2 diabetes (T2D).

RESEARCH DESIGN AND METHODS

This was a multicenter, randomized, open-label, three-arm trial comparing lixisenatide 20 µg and liraglutide 1.2 and 1.8 mg once daily for 8 weeks in combination with insulin glargine after optimized titration. The primary end point was change from baseline to week 8 in incremental area under the postprandial plasma glucose curve for 4 h after a standardized solid breakfast (AUC PPG0030-0430 h). Changes from baseline in gastric emptying, 24-h plasma glucose profile, HbA1c, fasting plasma glucose (FPG), 24-h ambulatory heart rate and blood pressure, amylase and lipase levels, and adverse events (AEs) were also assessed.

RESULTS

In total, 142 patients were randomized and treated. Lixisenatide 20 µg achieved greater reductions of AUC PPG0030-0430 h compared with liraglutide (marginal mean [95% one-sided CI] treatment difference, -6.0 [-7.8] h ⋅ mmol/L [-108.3 (-140.0) h ⋅ mg/dL] vs. liraglutide 1.2 mg and -4.6 [-6.3] h ⋅ mmol/L [-83.0 (-114.2) h ⋅ mg/dL] vs. liraglutide 1.8 mg; P < 0.001 for both), and gastric emptying was delayed to a greater extent than with liraglutide 1.2 and 1.8 mg (P < 0.001 for treatment comparisons). FPG was unchanged in all treatment arms. At week 8, mean ± SD HbA1c was 6.2 ± 0.4% (44 ± 5 mmol/mol), 6.1 ± 0.3% (44 ± 4 mmol/mol), and 6.1 ± 0.3% (44 ± 4 mmol/mol) for lixisenatide 20 µg and liraglutide 1.2 and 1.8 mg, respectively. At week 8, both liraglutide doses increased marginal mean ± SE 24-h heart rate from baseline by 9 ± 1 bpm vs. 3 ± 1 bpm with lixisenatide (P < 0.001). Occurrence of symptomatic hypoglycemia was higher with lixisenatide; gastrointestinal AEs were more common with liraglutide. Lipase levels were significantly increased from baseline with liraglutide 1.2 and 1.8 mg (marginal mean ± SE increase 21 ± 7 IU/L for both; P < 0.05).

CONCLUSIONS

Lixisenatide and liraglutide improved glycemic control in optimized insulin glargine-treated T2D albeit with contrasting mechanisms of action and differing safety profiles.