Dataset Information

The National Glycohemoglobin Standardization Program: Over 20 Years of Improving Hemoglobin A1c Measurement.

ABSTRACT: BACKGROUND:Measurement of hemoglobin A1c (HbA1c) in the blood is integral to and essential for the treatment of patients with diabetes mellitus. HbA1c reflects the mean blood glucose concentration over the preceding 8 to 12 weeks. Although the clinical value of HbA1c was initially limited by large differences in results among various methods, the investment of considerable effort to implement standardization has brought about a marked improvement in analysis. CONTENT:The focus of this review is on the substantial progress that has been achieved in enhancing the accuracy and, therefore, the clinical value of HbA1c assays. SUMMARY:The interactions between the National Glycohemoglobin Standardization Program and manufacturers of HbA1c methods have been instrumental in standardizing HbA1c. Proficiency testing using whole blood has allowed accuracy-based assessment of methods in individual clinical laboratories that has made an important contribution to improving the HbA1c measurement in patient samples. These initiatives, supported by the efforts of the IFCC network, have led to a continuing enhancement of HbA1c methods.Many of the factors that previously influenced HbA1c results independently of blood glucose have been eliminated from most modern methods. These include carbamylation, labile intermediates, and common hemoglobin variants. Nevertheless, some factors (e.g., race and aging) may alter HbA1c interpretation, but whether these differences have clinical implications remains contentious. HbA1c has a fundamental role in the diagnosis and management of diabetes. Ongoing improvements in HbA1c measurement and quality will further enhance the clinical value of this analyte.

SUBMITTER: Little RR

PROVIDER: S-EPMC6693326 | biostudies-literature | 2019 Jul

REPOSITORIES: biostudies-literature

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The National Glycohemoglobin Standardization Program: Over 20 Years of Improving Hemoglobin A<sub>1c</sub> Measurement.

Little Randie R RR Rohlfing Curt C Sacks David B DB

Clinical chemistry 20181205 7

<h4>Background</h4>Measurement of hemoglobin A1c (HbA<sub>1c</sub>) in the blood is integral to and essential for the treatment of patients with diabetes mellitus. HbA<sub>1c</sub> reflects the mean blood glucose concentration over the preceding 8 to 12 weeks. Although the clinical value of HbA<sub>1c</sub> was initially limited by large differences in results among various methods, the investment of considerable effort to implement standardization has brought about a marked improvement in analy ...[more]

PMID: 30518660

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Project description:BACKGROUND:The T1 Mapping and Extracellular volume (ECV) Standardization (T1MES) program explored T1 mapping quality assurance using a purpose-developed phantom with Food and Drug Administration (FDA) and Conformité Européenne (CE) regulatory clearance. We report T1 measurement repeatability across centers describing sequence, magnet, and vendor performance. METHODS:Phantoms batch-manufactured in August 2015 underwent 2?years of structural imaging, B0 and B1, and "reference" slow T1 testing. Temperature dependency was evaluated by the United States National Institute of Standards and Technology and by the German Physikalisch-Technische Bundesanstalt. Center-specific T1 mapping repeatability (maximum one scan per week to minimum one per quarter year) was assessed over mean 358 (maximum 1161) days on 34 1.5?T and 22 3?T magnets using multiple T1 mapping sequences. Image and temperature data were analyzed semi-automatically. Repeatability of serial T1 was evaluated in terms of coefficient of variation (CoV), and linear mixed models were constructed to study the interplay of some of the known sources of T1 variation. RESULTS:Over 2?years, phantom gel integrity remained intact (no rips/tears), B0 and B1 homogenous, and "reference" T1 stable compared to baseline (% change at 1.5?T, 1.95?±?1.39%; 3?T, 2.22?±?1.44%). Per degrees Celsius, 1.5?T, T1 (MOLLI 5s(3s)3s) increased by 11.4?ms in long native blood tubes and decreased by 1.2?ms in short post-contrast myocardium tubes. Agreement of estimated T1 times with "reference" T1 was similar across Siemens and Philips CMR systems at both field strengths (adjusted R2 ranges for both field strengths, 0.99-1.00). Over 1?year, many 1.5?T and 3?T sequences/magnets were repeatable with mean CoVs <?1 and 2% respectively. Repeatability was narrower for 1.5?T over 3?T. Within T1MES repeatability for native T1 was narrow for several sequences, for example, at 1.5?T, Siemens MOLLI 5s(3s)3s prototype number 448B (mean CoV?=?0.27%) and Philips modified Look-Locker inversion recovery (MOLLI) 3s(3s)5s (CoV 0.54%), and at 3?T, Philips MOLLI 3b(3s)5b (CoV 0.33%) and Siemens shortened MOLLI (ShMOLLI) prototype 780C (CoV 0.69%). After adjusting for temperature and field strength, it was found that the T1 mapping sequence and scanner software version (both P?<?0.001 at 1.5?T and 3?T), and to a lesser extent the scanner model (P?=?0.011, 1.5?T only), had the greatest influence on T1 across multiple centers. CONCLUSION:The T1MES CE/FDA approved phantom is a robust quality assurance device. In a multi-center setting, T1 mapping had performance differences between field strengths, sequences, scanner software versions, and manufacturers. However, several specific combinations of field strength, sequence, and scanner are highly repeatable, and thus, have potential to provide standardized assessment of T1 times for clinical use, although temperature correction is required for native T1 tubes at least.

Project description:Objective: We aimed to identify hemoglobin A1c (HbA1c)-associated genetic variants and examine their implications for glycemic status evaluated by HbA1c in U.S. Hispanics/Latinos with diverse genetic ancestries.Research design and methods: We conducted a genome-wide association study (GWAS) of HbA1c in 9,636 U.S. Hispanics/Latinos without diabetes from the Hispanic Community Health Study/Study of Latinos, followed by a replication among 4,729 U.S. Hispanics/Latinos from three independent studies.Results: Our GWAS and replication analyses showed 10 previously known and novel loci associated with HbA1c at genome-wide significance levels (P < 5.0 × 10-8). In particular, two African ancestry-specific variants, HBB-rs334 and G6PD-rs1050828, which are causal mutations for sickle cell disease and G6PD deficiency, respectively, had ?10 times larger effect sizes on HbA1c levels (? = -0.31% [-3.4 mmol/mol]) and -0.35% [-3.8 mmol/mol] per minor allele, respectively) compared with other HbA1c-associated variants (0.03-0.04% [0.3-0.4 mmol/mol] per allele). A novel Amerindian ancestry-specific variant, HBM-rs145546625, was associated with HbA1c and hematologic traits but not with fasting glucose. The prevalence of hyperglycemia (prediabetes and diabetes) defined using fasting glucose or oral glucose tolerance test 2-h glucose was similar between carriers of HBB-rs334 or G6PD-rs1050828 HbA1c-lowering alleles and noncarriers, whereas the prevalence of hyperglycemia defined using HbA1c was significantly lower in carriers than in noncarriers (12.2% vs. 28.4%, P < 0.001). After recalibration of the HbA1c level taking HBB-rs334 and G6PD-rs1050828 into account, the prevalence of hyperglycemia in carriers was similar to noncarriers (31.3% vs. 28.4%, P = 0.28).Conclusions: This study in U.S. Hispanics/Latinos found several ancestry-specific alleles associated with HbA1c through erythrocyte-related rather than glycemic-related pathways. The potential influences of these nonglycemic-related variants need to be considered when the HbA1c test is performed.

Dataset Information

The National Glycohemoglobin Standardization Program: Over 20 Years of Improving Hemoglobin A1c Measurement.

Publications

The National Glycohemoglobin Standardization Program: Over 20 Years of Improving Hemoglobin A<sub>1c</sub> Measurement.

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