IFCC Reference Measurement Procedure Research Articles

A-080 Overcoming Challenges of Equilibrium Dialysis-Based Free Thyroxine Measurements

Abstract Background Thyroid function tests are widely used to detect diseases of the thyroid. Concerns about the accuracy and reliability of free thyroxine (FT4) measurements have been stated by the clinical laboratory community. To address these concerns, CDC established a reference measurement procedure (RMP) for FT4 based on equilibrium dialysis (ED). ED-based methods have advantages over traditional direct immunoassays. As with all analytical methods, factors affecting accuracy and reliability of ED-based methods need identification and understanding. To investigate potential sources of error, the CDC FT4 RMP was used to evaluate T4 stability at different of storage conditions, adsorption of FT4 to common labware surfaces, and the effect of dialysis membrane materials on the measured FT4 in serum. Methods FT4 was measured in serum using the IFCC RMP (1). FT4 was separated from the protein-bound form during the equilibrium dialysis step of the RMP. Dialysates were spiked with internal standard (13C6-T4) and the analyte was further isolated by C18 solid phase extraction (SPE) and liquid-liquid extraction (LLE) in ethyl acetate prior to injection on an UHPLC system coupled with a triple quadrupole mass spectrometer. Bracketed calibration and primary reference materials were used to determine FT4 concentration in serum. This procedure was used to evaluate stability of serum FT4 during storage at −70 to 5 °C. Short- and long-term T4 stability of calibrator solutions at −70 °C to ambient temperature and the extent of adsorption of T4 calibrator solutions to the commonly used labware surfaces were evaluated. Furthermore, the suitability of 4 different dialysis membranes was assessed. In addition, three alternatives to the currently used SPE and LLE extraction steps were tested: LLE using cyclohexane and ethyl acetate, LLE with ethyl acetate, and supported liquid extraction with cyclohexane and ethyl acetate. Results T4 calibrator solution was stable in 1.7% ammonium hydroxide in ethanol for at least 2.9 years at −70 °C and up to 7 days at ambient temperature. Exposure of various calibrator solutions such as T4 in ethanol, ethanol with 1.7% ammonium hydroxide, 10% acetonitrile with 0.1% formic acid to common labware resulted in up to 10.1% loss of the analyte. FT4 in serum and T4 in dialysates and extracts were stable at −70 to 5 °C. Use of alternative dialysis membranes resulted in up to −8.8% mean bias to the reference membranes. Recoveries of the analyte using four extraction methods were 85.4%–95.0%. None of the tested extraction conditions significantly changed the results obtained with the original FT4 RMPs. Conclusion Although FT4 RMP must strictly adhere to the ED conditions described for the RMP, other parts of the sample preparation procedures can deviate from the originally published procedure. Careful selection of procedure for calibrator solvents, dialysis membranes, labware, and storage conditions is required to ensure accurate and reproducible FT4 measurements.

Validation of metrological traceability of the new generation of Abbott Alinity alkaline phosphatase assay.

Recently, Abbott Diagnostics marketed a new generation of Alinity enzyme assays, introducing a multiparametric calibrator [Consolidated Chemistry Calibrator (ConCC)] in place of or in addition to factor-based calibrations. For alkaline phosphatase (ALP), both calibration options are offered, i.e.,with ConCC (ALP2) and with an experimental calibration factor (ALP2F). Both options are declared traceable to the 2011 IFCC reference measurement procedure (RMP). Before to replace the old generation (ALP1) with the new one, we decided to validate the trueness of ALP2/ALP2F. Three approaches were employed: (a)preliminary comparison on 48 native frozen serum samples with ALP1, of which traceability to RMP was previously successfully verified; (b)examination of three banked serum pools (BSP) with values assigned by RMP; (c)direct comparison with RMP on a set of 24 fresh serum samples. Bias estimation and regression studies were performed, and the standard measurement uncertainty associated with ALP measurements on clinical samples (uresult) was estimated and compared with established analytical performance specifications (APS). ConCC commutability was also assessed. A positive proportional bias was found with both ALP2 and ALP2F when compared to ALP1 and RMP. This positive bias was confirmed on BSP: in average, +13.1 % for ALP2 and +10.0 % for ALP2F, respectively. uresult were 13.28 % for ALP2 and 10.04 % for ALP2F, both not fulfilling the minimum APS of 4.0 %. Furthermore, ConCC was not commutable with clinical samples. Our results unearth problems in the correct implementation of traceability of Alinity ALP2/ALP2F, with the risk for the new assay to be unfit for clinical purposes.

The ALT upper reference interval debate: Blame it on the alcohol

BackgroundIn 2017, the American College of Gastroenterology (ACG) and the North American Society of Pediatric Gastroenterology, Hepatology and Nutrition published clinical guidelines recommending the use of alanine aminotransferase (ALT) upper reference limits (URL) of 33, 25, 26, and 22 U/l for men, women, boys, and girls, respectively. This was opposed by laboratory experts who advocated for the use of higher URL of 59, 41, 33, and 24 U/l instead. We suspected that the variable inclusion of individuals who consumed alcohol to be a major contributing source of URL variability and debate. MethodsOutpatient ALT data (n = 7379) were collected from unique individuals ≥13 y with BMIs of ≥19 and ≤25. A total of 222 (3%) were excluded due to suspected liver disease. Patients were split into a pediatric group (age 13–17 y), an alcohol-restricted adult group (age 18–20 y), and adults with access to alcohol by decade (i.e., age 21–29, 30–39, 40–49, 50–59, 60–69, 70–79, and ≥ 80 y). All ALT values were measured on Roche Cobas 8000 with pyridoxal phosphate and traceable to the IFCC-reference measurement procedure. ResultsWe derived URL similar to CALIPER for our pediatric population, but closer to ACG-proposed URL in our alcohol-restricted adult group. The URL increased significantly in men and women for all other age groups. ConclusionsThe discrepancy in ALT URL in clinical laboratories may be attributable in part due to the variable inclusion of individuals who recently consumed alcohol in local population derivation studies.

Analytical performance evaluation of the Norudia HbA1c assay.

BackgroundHemoglobin A1c (HbA1c) is arguably the most important biomarker used in the diagnosis and treatment monitoring of diabetes mellitus. We evaluated the analytical performance of the Norudia HbA1c assay (Sekisui Medical Co., LTD), which uses an enzymatic method incorporated into a fully automated, high‐throughput system.MethodsThe precision, linearity, and carryover of the Norudia HbA1c assay were evaluated. Using 60 patient samples, comparative analysis of HbA1c measurements with two commonly used HbA1c assays, the D100 (Bio‐Rad Laboratories, Inc) and HLC‐723 G11 (Tosoh), was undergone. Thirteen commutable samples with known HbA1c concentrations measured using an IFCC reference measurement procedure were used to compare accuracy between methods. Interference of HbA1c measurement by Hb variants was evaluated using 16 known Hb variant samples.ResultsRepeatability (% CV) for low and high concentrations ranged from 1.12%‐1.50% and 0.66%‐0.75%, respectively, and within‐laboratory precision for low and high concentrations ranged from 1.73%‐2.89% and 0.98%‐1.64%, respectively. For linearity, the coefficient of determination was 0.9987. No significant carryover was observed. When compared to the D100 and HLC‐723 G11 assays, the Norudia HbA1c assay showed the best accuracy with the lowest mean bias (−1.72%). Furthermore, the Norudia was least affected by Hb variants and gave the most reliable HbA1c measurements.ConclusionThe Norudia HbA1c showed excellent analytical performance with good precision and linearity, and minimal carryover. When compared to other routine HbA1c methods, the Norudia HbA1c assay showed the highest accuracy and was least affected by Hb variants.

Trueness assessment of HbA1c routine assays: are processed EQA materials up to the job?

Background With the worldwide increase of diabetes mellitus prevalence, ensuring that HbA1c assays are accurate is essential. External quality assessment (EQA) programs enable laboratories to verify that analytical methods perform according to the manufacturers' specifications. However, assessing trueness requires commutable materials, a property that is rarely characterized for EQA materials. Methods The difference in bias approach was used to assess commutability of 26 processed quality control materials for 17 of the most frequently used HbA1c assays. Involved assays included immuno-assays, enzymatic assays, affinity, ion-exchange HPLC boronate affinity HPLC and capillary electrophoresis. The measurements were performed at manufacturers or expert laboratories. Assay trueness was additionally assessed against the IFCC reference measurement procedure using fresh clinical specimens that were distributed to 450 medical laboratories. Results Commutability of processed EQA materials was highly heterogeneous and globally insufficient to rigorously assess the trueness of HbA1c assays. Using fresh clinical specimens, mean bias was -0.13 mmol/mol for low HbA1c (34 mmol/mol), between +1.0 and +1.3 mmol/mol for intermediate HbA1c (49 and 58 mmol/mol) and +1.2 mmol/mol for elevated HbA1c (90 mmol/mol). Conclusions This study demonstrates that due to insufficient commutability, most processed EQA materials are unsuitable to assess trueness of HbA1c assays and agreement between the different assays. These materials can only provide information on comparability of individual laboratory results with its peers and on assay precision. Using fresh whole blood samples, this study additionally shows that most HbA1c assays are fairly accurate and meet the total allowable error quality target of 5 mmol/mol.

Hb variants in Korea: effect on HbA1c using five routine methods.

Quantification of glycated hemoglobin (HbA1c) is a challenge in patients with hemoglobin (Hb) variants. We evaluated the impact of various Hb variants on five routine HbA1c assays by comparing with the IFCC reference measurement procedure (RMP). Whole blood samples showing warning flags or no results on routine HPLC HbA1c assays were confirmed for Hb variants and were submitted to HbA1c quantification using Sebia Capillarys 2 Flex Piercing, Roche Tina-quant HbA1c Gen. 2, Bio-Rad Variant II Turbo 2.0, ADAMS HA-8180, Tosoh G8 standard mode, and IFCC RMP using LC-MS. Among 114 samples, the most common variants were Hb G-Coushatta (n=47), Queens (n=41), Ube-4 (n=11), Chad (n=4), Yamagata (n=4), G-His-Tsou (n=2), G-Taipei (n=1), Fort de France (n=1), Hoshida (n=1), and two novel variants (Hb α-globin, HBA 52 Gly>Cys and Hb β-globin, HBB 146 His>Asn). In terms of control samples, all the result of HbA1c were "acceptable", within the criteria of ±7% compared to IFCC RMP target values. However, percentage of "unacceptable" results of samples with Hb variants were 16% for Capillarys 2, 7% for Tina-quant, 51% for Variant II Turbo 2.0, 95% for G8 standard mode, and 89% for HA-8180. The Capillarys 2 and HA-8180 assay did not provide the results in 5 and 40 samples with Hb variants, respectively. HbA1c results from five routine assays in patients with relatively common Hb variants in Korea showed various degrees of bias compared to those of IFCC RMP. Therefore, laboratories should be aware of the limitation of their methods with respect to interference from Hb variants found commonly in their local population and suggest an alternative HbA1c quantification method.

Modified HPLC-ESI-MS Method for Glycated Hemoglobin Quantification Based on the IFCC Reference Measurement Procedure and Its Application for Quantitative Analyses in Clinical Laboratories of China.

The level of glycated hemoglobin (HbA1c ) has been recognized as an important indicator of long-term glycemic control. However, the HbA1c measurement is not currently included as a diagnostic determinant in China. Current study aims to assess a candidate modified International Federation of Clinical Chemistry reference method for the forthcoming standardization of HbA1c measurements in China. The HbA1c concentration was measured using a modified high-performance liquid chromatography-electrospray ionization-mass spectrometry (HPLC-ESI-MS) method. The modified method replaces the propylcyanide column with a C18 reversed-phase column, which has a lower cost and is more commonly used in China, and uses 0.1% (26.5 mmol/l) formic acid instead of trifluoroacetic acid. Moreover, in order to minimize matrix interference and reduce the running time, a solid-phase extraction was employed. The discrepancies between HbA1c measurements using conventional methods and the HPLC-ESI-MS method were clarified in clinical samples from healthy people and diabetic patients. Corresponding samples were distributed to 89 hospitals in Beijing for external quality assessment. The linearity, reliability, and accuracy of the modified HPLC-ESI-MS method with a shortened running time of 6 min were successfully validated. Out of 89 hospitals evaluated, the relative biases of HbA1c concentrations were < 8% for 74 hospitals and < 5% for 60 hospitals. Compared with other conventional methods, HbA1c concentrations determined by HPLC methods were similar to the values obtained from the current HPLC-ESI-MS method. The HPLC-ESI-MS method represents an improvement over existing methods and provides a simple, stable, and rapid HbA1c measurement with strong signal intensities and reduced ion suppression.

Performance of glycated hemoglobin (HbA1c) methods evaluated with EQAS studies using fresh blood samples: Still space for improvements

BackgroundThe determination of glycated hemoglobin is a key indicator for the management of diabetic patients. A reference measurement system for its determination is available and IVD manufacturers should have aligned their assay to this system. MethodsTwo fresh blood samples were distributed by courier to 206 Italian laboratories asking for the determination of their HbA1c concentration. Target HbA1c values were assigned by the IFCC reference measurement procedure. ResultsFrom 193 laboratories using analytical systems from five manufacturers (Bio-Rad Laboratories, A. Menarini Diagnostics, Roche Diagnostics, Sebia and Tosoh), we obtained a global variability of 5.3% (in terms of CV) and of 3.8% at an HbA1c value of 37.4mmol/mol (sample 1) and 62.0mmol/mol (sample 2), respectively. With a goal for the allowable total error (TE) of 6.0%, 70% and 77% of the participants met this criterion for samples 1 and 2, respectively. Inter-laboratory CVs, were between 3.3 and 5.0% and between 2.2 and 3.7% for samples 1 and 2, respectively. Tosoh users registered the smallest inter-laboratory CV in sample 1, and Sebia's in sample 2. With regard to trueness, all methods had a mean bias of ≤2.8% with respect to the target values, with the exception of Tosoh (bias of +6.1 and +5.8%, for samples 1 and 2, respectively). ConclusionThese results are in good agreement with those obtained by the CAP 2014 GH2-A survey, suggesting then that still there is an urgent need for improving a significant part of the methods currently used to measure HbA1c.

Quantification of hemoglobin A1c by off-line HPLC separation and liquid chromatography-tandem mass spectrometry: a modification of the IFCC reference measurement procedure

The quality of hemoglobin A1c measurement is very important in the management of diabetes. A reference system has been established by the IFCC Working Group on HbA1c Standardization. We did some modification of the IFCC Reference Measurement Procedure with MS detection which significantly decreased the analysis time and improved the precision of the analytes by off-line HPLC separation and liquid chromatography-tandem mass spectrometry (LC/MS/MS) analysis. The samples were prepared and enzymatically cleaved according to the IFCC HbA1c reference measurement procedure. Then the digest solution was injected to a reversed phase HPLC for purification and a clean fraction was collected. The fraction was analyzed by liquid chromatography-tandem mass spectrometry with an isocratic elution on a C18 column. Liner regression was used to determine the concentration of HbA1c. The total analysis time which includes the off-line HPLC separation and the LC/MS/MS analysis was reduced by at least 65% compared to the existing IFCC method. The transitions of m/z 348.4→237.2 and m/z 429.4→245.2 were selected for quantification of non-glycated and glycated hexapeptide. Fifty seven hemolysate samples used in recent 3-years' IFCC HbA1c inter-laboratory studies (2012-2014) were analyzed by the LC/MS/MS procedure for method validation. The CVS were between 0.16% and 1.87% for 4 measurements per sample in the concentration range for HbA1c between 30.4 and 145.8 mmol/mol. The relative bias of the LC/MS/MS method was varied from -3.21% to 2.47% compared to the IFCC network assigned values. This method is an efficient and reliable procedure for the determination of HbA1c. After thorough evaluation within the IFCC Network this modification may be implemented in the IFCC RMP for HbA1c with MS detection.

Development of reference intervals for serum alkaline phosphatase among adults in Southern China traced to the new IFCC reference measurement procedure.

Serum alkaline phosphatase (ALP) plays a critical role in the diagnosis of various diseases, and the establishment of relevant, reliable reference intervals (RI) is key to avoiding misdiagnoses. In 2011, IFCC published the new reference measurement procedure (RMP) for the determination of serum ALP in which one of the main modifications was the measuring temperature of the assay. Here, the new RMP was used to help establish RIs for serum ALP concentrations in healthy Chinese Han. Volunteer individuals in Guangdong province, China (n=1622) were screened by questionnaire and laboratory testing for eligibility as a reference. Blood (20 mL) was collected and samples were measured by the Roche Modular system using the new RMP for the serum ALP compatible method. Partitioning of values by gender and/or age was evaluated with a standard normal deviate test after removing outliers. A simple non-parametric method for a two-sided 95% distribution of reference values was calculated. Serum ALP concentrations were obtained from the cohort of eligible reference individuals (n=658). The RI for serum ALP in males age 18-79 years was 48-131 U/L. Females were partitioned into two age groups based on statistical analysis, 18-49 years and 50-79 years, and the RIs derived were 40-106 U/L and 57-159 U/L, respectively. RIs for serum ALP for Chinese Han individuals in between the ages of 18 and 79 years were determined and required partitioning due to the higher ALP values of females age 50-79 years.

In vitro determination of hemoglobin A1c for diabetes diagnosis and management: technology update

In vitro determination of hemoglobin A1c for diabetes diagnosis and management: technology update Emma English,1 Elise T Milosevich,1 W Garry John2 1School of Medicine, University of Nottingham, Royal Derby Hospital, Derby, United Kingdom; 2Department of Clinical Biochemistry, Norfolk and Norwich University Hospital, Norwich, United Kingdom Abstract: It is fascinating to consider the analytical improvements that have occurred since glycated hemoglobin was first used in routine clinical laboratories for diabetes monitoring around 1977; at that time methods displayed poor precision, there were no calibrators or material with assayed values for quality control purposes. This review outlines the major improvements in hemoglobin A1c (HbA1c) measurement that have occurred since its introduction, and reflects on the increased importance of this hemoglobin fraction in the monitoring of glycemic control. The use of HbA1c as a diagnostic tool is discussed in addition to its use in monitoring the patient with diabetes; the biochemistry of HbA1c formation is described, and how these changes to the hemoglobin molecule have been used to develop methods to measure this fraction. Standardization of HbA1c is described in detail; the development of the IFCC Reference Measurement Procedure for HbA1c has enabled global standardization to be achieved which has allowed global targets to be set for glycemic control and diagnosis. The importance of factors that may interfere in the measurement of HbA1c are highlighted. Keywords: glycated hemoglobin, HbA1c, IFCC

Comparación entre 2 sistemas analíticos para la determinación de la hemoglobina A1c: inmunoturbidimetría versus cromatografía líquida de alta eficiencia

IntroductionHemoglobin A1c (HbA1c) is widely used to assess glycemic status in patients with diabetes mellitus. The purpose of this study was to compare 2 automated analytical systems to measure HbA1c that use different measurement principles, evaluating the correlation between the two methods, as well as their ease of use. MethodsA total of 622 samples were analyzed using 2 methods: high performance liquid chromatography (HPLC) (analyzer ADAMS A1c HA-8160; A. Menarini Diagnostics, Italy) and an immunoturbidimetric assay (Tina-quant Hemoglobin A1c Gen.3, Cobas 6000 analyzer; Roche Diagnostics, Switzerland). Both methods were calibrated in accordance with IFCC reference measurement procedure. The correlation between the two methods was assessed by least squares and Passing-Bablok linear regression analyses (R program v.2.11.1). The daily start-up time of the 2 instruments used, daily maintenance tasks, and determination of throughput were also recorded. ResultsThere was a strong correlation between the results generated by the two test methods using both the least squares (intercept 0.54; slope 0.98) and Passing-Bablok (intercept 0.10; slope 1.00) regression methods. The time spent daily for the start-up of the HA-8160 analyzer was 25min and completion time was 15min. Maintenance tasks for the Cobas 6000 analyzer at the beginning and end of the day are automated processes. The throughput for the HA-8160 analyzer was 20 samples/h, and 100 samples/h for the Cobas 6000 analyzer. The HPLC method also included a time-consuming manual analysis of each chromatogram. ConclusionsAn excellent correlation was observed between the HPLC and immunoturbidimetric methods. The advantages of the immunoturbidimetric method are optimization of processing time of HbA1c tests and a reduction in the unit cost per test.

Liquid Chromatography–Isotope Dilution–Mass Spectrometry as a New Basis for the Reference Measurement Procedure for Hemoglobin A1c Determination

Standardization of hemoglobin (Hb)A(1c) measurements is a process of considerable interest for quality assurance in diabetes management. To contribute to continuous quality improvement and fulfillment of the requirements for reference measurement procedures according to the standards of the International Organization for Standardization, we developed a calibration system of highest metrological order using isotope dilution-mass spectrometry with a reference material. Samples were prepared by enzymatic cleavage based on the IFCC reference measurement procedure for LC-MS analysis. After digestion the samples were spiked with [D7]-labeled glycated and nonglycated hexapeptides as internal standards for quantification. LC-MS analysis was performed by using a C12 reversed-phase column and a gradient of acetonitrile/H(2)O containing 0.1% formic acid. Calibration systems for HbA(1c) determination based on liquid chromatography-isotope dilution-mass spectrometry (LC-ID-MS) and on the IFCC reference measurement procedure were compared. A linear regression analysis demonstrated a correlation of r(2) = 1.00 between the 2 different calibration systems. Mean deviation was 5.5% for the calibration and 3.3% for hemolysate samples, with a mean expanded uncertainty of 4.9%. This LC-ID-MS procedure allows the current IFCC reference measurement procedure for HbA(1c) to be raised to a higher order of accuracy.

Statistical Methods for Monitoring the Relationship between the IFCC Reference Measurement Procedure for Hemoglobin A1c and the Designated Comparison Methods in the United States, Japan, and Sweden

The American Diabetes Association (ADA)/European Association for the Study of Diabetes (EASD)/International Diabetes Federation (IDF)/IFCC Consensus Statement on the worldwide standardization of HbA(1c) states that "... [HbA(1c)] results are to be reported world-wide in IFCC units ... and derived NGSP units ... , using the IFCC-NGSP master equation." We describe statistical methods to evaluate and monitor the relationships as expressed in master equations (MEs) between the IFCC Reference Measurement procedure (IFCC-RM) and designated comparison methods (DCMs) [US National Glycohemoglobin Standardization Program (NGSP), Japanese Diabetes Society/Japanese Society for Clinical Chemistry (JDS/JSCC), and Mono-S in Sweden]. We applied these statistics, including uncertainty calculations, to 12 studies in which networks of reference laboratories participated, operating the IFCC-RM and DCMs. For NGSP and Mono-S, slope, intercept, and derived percentage HbA(1c) at the therapeutic target show compliance with the respective MEs in all 12 studies. For JDS/JSCC, a slight deviation is seen in slope and derived percentage HbA(1c) in 2 of the 12 studies. Using the MEs, the uncertainty in an assigned value increases from 0.42 mmol/mol HbA(1c) (IFCC-RM) to 0.47 (NGSP), 0.49 (JDS/JSCC), and 0.51 (Mono-S). We describe sound statistical methods for the investigation of relations between networks of reference laboratories. Application of these statistical methods to the relationship between the IFCC-RM and DCMs in the US, Japan, and Sweden shows that they are suitable for the purpose, and the results support the applicability of the ADA/EASD/IDF/IFCC Consensus Statement on HbA1c measurement.

Modified HPLC-Electrospray Ionization/Mass Spectrometry Method for HbA1c Based on IFCC Reference Measurement Procedure

Monitoring of hemoglobin A(1c) (HbA(1c)) is important in the management of diabetes. The IFCC reference measurement procedure for HbA(1c) is based on the ratio of glycated to nonglycated N-terminal hexapeptides of the beta-chains of hemoglobin after digestion with Glu-C endoproteinase. We developed a modification of the original reference measurement procedure with HPLC-electrospray ionization/mass spectrometry (ESI/MS). We performed chromatographic separation of the hexapeptides using a C12 reversed-phase column and a binary gradient system consisting of a mixture of H(2)O/acetonitrile/formic acid. Using this method, we obtained higher signal intensities and improved system stability compared with the reference measurement procedure. In the range of 3% to 14% HbA(1c), intralaboratory CVs were 0.71% to 1.86%. Deviations from IFCC target values were -0.87 to 1.00 relative %. These values fulfill acceptability criteria for HbA(1c) determination set by the IFCC Working Group on HbA(1c) Standardization. This procedure for the determination of HbA(1c) improves the existing reference measurement procedure.

Global standardization of glycated hemoglobin measurement: the position of the IFCC Working Group

The measurement of glycated hemoglobin is central in the monitoring of glycemic control in patients with diabetes. There are at least 30 different laboratory assays commercially available to measure the proportion of HbA1c in blood. In 1995 the IFCC established a Working Group (IFCC WG-HbA1c) to achieve international standardization of HbA1c measurement. The main achievements can be summarized as follows: a) a reference measurement procedure has been established with purified primary calibrators; b) a network of reference laboratories has been developed worldwide; and c) work has begun on implementation of traceability to the IFCC reference system. The IFCC WG-HbA1c recognizes the recommendation of the IFCC-IUPAC Committee on Nomenclature, Properties and Units that the analyte measured by the IFCC reference measurement procedure has been defined as betaN1-deoxyfructosyl-hemoglobin and that the recommended measurement units are mmol/mol. The IFCC WG-HbA1c recommends maintaining the use of the name HbA1c in clinical practice.