Quality of HbA1c Measurement in the Practice: The German Perspective

Hemoglobin A1c (HbA1c) measurement has come to be a cornerstone in modern diabetes therapy. However, the methodological aspects of this type of measurement have been given little attention lately due to its position as an established method of choice. Nevertheless, quite a number of issues face practical application, such as clinically relevant differences between different measurement methods--both lab-based and point-of-care (POCT) systems will show better or worse diabetes management results after switching methods; and there are a number of possible reasons that need to be known and observed in practice. The aim of this review is to draw attention to these problems from a German point of view and provide suggestions for appropriate measures to improve the situation.

Report on HbA1c Proficiency Testing in Asia in 2012

In 2010, the Japan Diabetes Society decided to introduce the National Glycohemoglobin Standardization Program (NGSP) values into clinical practice. Accordingly, NGSP Certification of Japanese manufacturers of HbA1c-related diagnostic reagents and instruments was initiated in February, 2012, through an NGSP network laboratory, the Asian Secondary Reference Laboratory (ASRL) #1. Traceability to the NGSP reference system can be endorsed by manufacturer certification, as well as by the College of American Pathologists (CAP) survey. Nevertheless, only a few manufacturers participate in the CAP survey in Japan. Thus, proficiency testing (PT) was proposed and executed by ASRL #1. Single-donor whole-blood samples were used for the PT. The participated measurement systems were NGSP certified. Twenty-two laboratories obtained certification through ASRL #1; 2 through the Secondary Reference Laboratory (SRL) #8; and 9 through the SRL #9. The combination plots of the bias data in this PT and in the NGSP certification performed in March and May in 2012 were consistent with each other: mean NGSP values at each level agreed well with the target value. In conclusion, PT using whole blood is useful in endorsing NGSP certification.

From biomarkers to medical tests: the changing landscape of test evaluation

Regulators and healthcare payers are increasingly demanding evidence that biomarkers deliver patient benefits to justify their use in clinical practice. Laboratory professionals need to be familiar with these evidence requirements to better engage in biomarker research and decisions about their appropriate use. This paper by a multidisciplinary group of the European Federation of Clinical Chemistry and Laboratory Medicine describes the pathway of a laboratory assay measuring a biomarker to becoming a medically useful test. We define the key terms, principles and components of the test evaluation process. Unlike previously described linearly staged models, we illustrate how the essential components of analytical and clinical performances, clinical and cost-effectiveness and the broader impact of testing assemble in a dynamic cycle. We highlight the importance of defining clinical goals and how the intended application of the biomarker in the clinical pathway should drive each component of test evaluation. This approach emphasizes the interaction of the different components, and that clinical effectiveness data should be fed back to refine analytical and clinical performances to achieve improved outcomes. The framework aims to support the understanding of key stakeholders. The laboratory profession needs to strengthen collaboration with industry and experts in evidence-based medicine, regulatory bodies and policy makers for better decisions about the use of new and existing medical tests.

Liver enzymes but not free fatty acid levels predict markers of insulin sensitivity in overweight and obese, nondiabetic adults

Although obesity is a key predisposing risk factor in the development of insulin resistance (IR) and type 2 diabetes mellitus, not all obese individuals develop IR. This study aimed to identify key anthropometric and biochemical parameters that predict insulin sensitivity in overweight and obese adults. Based on previous literature, we hypothesized that markers of insulin sensitivity would be negatively correlated with plasma concentrations of free fatty acids and liver enzymes. Forty nondiabetic adult participants (body mass index ≥ 25.0 kg/m²) were recruited. Data collection included anthropometric measurements and fasting plasma samples for the quantification of liver enzymes (alanine transaminase, aspartate transaminase, γ-glutamyl transpeptidase), blood lipid profile, and markers of insulin sensitivity. Questionnaires relating to dietary intake, physical activity, and fatigue were also completed. Insulin and Homeostasis Model of Assessment (HOMA) scores were significantly correlated with indirect measures of central obesity (P < .05). Glycosylated hemoglobin, insulin, and HOMA scores for IR were all positively correlated with selected liver function markers (P < .05). Scores of HOMA-IR were significantly positively correlated with plasma phospholipid levels of n-3 fatty acids (P = .04) and ratio of n-3/n-6 fatty acids (P < .05) and negatively correlated with n-6 fatty acids (P = .03). No significant correlations were found between markers of insulin sensitivity and cholesterol levels, physical activity, or self-reported fatigue. These results have reinforced the integral role of liver function in the development of IR. Despite previous data linking elevations in free fatty acid to the development of IR, we found no relationship between these variables in this study.

Multicenter evaluation of hemoglobin A1c assay on capillary electrophoresis

BACKGROUND

Hemoglobin A1c (HbA1c) measurement is currently used for the routine monitoring of long-term glycemic status, thus playing a fundamental role in the management of this disease. Since this marker has recently been recommended as an additional tool for diagnosing diabetes, it's of the utmost importance to ensure that the precision and accuracy of HbA1c methods are satisfactory.

METHODS

We assessed the analytical performances of the Capillarys 2 Flex Piercing® analyzer and compared the results obtained with those from two other widely used HPLC instruments. Furthermore, we evaluated the convenience and ergonomics of the system in authentic routine work conditions in three centers.

RESULTS

Within-laboratory (n=40) and between-laboratory (n=120) imprecision CV% using four blood samples with different concentrations of HbA1c were <3.4% and <3.1% using IFCC units and <2.1% and <2.0% using NGSP units, respectively. The obtained trueness (<3 mmol/mol, <0.3%) was highly satisfactory, nor was HbA1c measurement compromised by the presence of the commonly present hemoglobinopathies. The comparison made with established methods revealed excellent agreement (r>0.985).

CONCLUSIONS

The evaluated method is precise, accurate and robust, with a high throughput. It also allows the identification of the most frequent Hb variants and therefore may be a valid alternative to other methods currently proposed for routine use in clinical laboratories.

Serum uric acid in relation to serum 1,5-anhydroglucitol levels in patients with and without type 2 diabetes mellitus

OBJECTIVES

The aim of this study was to examine the relationship between serum levels of uric acid (UA) and 1,5-anhydroglucitol (1,5-AG) in elderly subjects (60 years or older; mean age, 73.0±7.2 years) with and without type 2 diabetes mellitus (DM).

METHODS

Subjects with DM (n=97) and without DM (n=360) were recruited from among our outpatients (estimated glomerular filtration rate≥45 mL min⁻¹ 1.73 m⁻², and urine protein equivalent to <1.0 g/L), and a cross-sectional study was performed with simple linear regression and stepwise multiple linear regression analyses.

RESULTS

The mean serum UA levels of men were significantly higher than those of women in both groups. The mean serum 1,5-AG levels of men were significantly higher than those of women in the non-DM group. There were positive correlations (indicated by Pearson's correlation coefficients) between serum UA levels and 1,5-anhydroglucitol levels in all patients and in both men and women. Simple linear regression and multiple linear regression analyses showed that the serum 1,5-AG levels were significantly and positively correlated with the serum UA level in both the non-DM group and the DM group. In the non-DM group, HbA1c levels, as well as 1,5-AG levels, were positively correlated with serum UA levels. Furthermore, the correlation between 1,5-AG and UA levels was stronger in subjects with DM than in subjects without DM.

CONCLUSIONS

These results suggest that the serum 1,5-AG level is an independent factor associated with serum UA levels in the nondiabetic state, as in DM.