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Lenters-Westra E.,Isala Klinieken | Lenters-Westra E.,European Reference Laboratory for Glycohemoglobin | Weykamp C.,European Reference Laboratory for Glycohemoglobin | Schindhelm R.K.,Isala Klinieken | And 5 more authors.
Diabetes Technology and Therapeutics | Year: 2011

Background: We assessed the reference change value (RCV) of currently available hemoglobin A1c (HbA1c) laboratory assays, which is defined as the critical difference between two consecutive HbA1c measurements representing a significant change in health status. Methods: We examined the individual laboratory coefficients of variation (CVs) in the Dutch/Belgian quality scheme based on 24 lyophilized samples and calculated the RCV per laboratory (n=220) and per assay method. In addition, two pooled whole blood samples were sent to the participating laboratories. The individual laboratory results were compared to the assigned value±an allowable total error (TEa) of 6%. Results: At HbA1c values of 41.0 mmol/mol (5.9%-Diabetes Control and Complications Trial [DCCT]) and 61.8 mmol/mol (7.8%-DCCT), 99% and 98%, respectively, of the laboratories reported a value within a TEa limit of 6%. The analytical CV of the HbA 1c method used in 78% of the laboratories is <2.4%. The mean RCV at an HbA1c value of 53 mmol/mol (7.0%-DCCT) for methods of Bio-Rad is 5.9 mmol/mol (0.59%-DCCT); for Arkray/Menarini, 4.3 mmol/mol (0.43%-DCCT); for Roche, 6.5 mmol/mol (0.65%-DCCT); for Tosoh, 3.3 mmol/mol (0.33%-DCCT); and for other methods, 6.3 mmol/mol (0.63%-DCCT). Conclusions: The analytical performance of the majority of laboratory HbA1c methods is within the clinical requirements. However, based on the calculated RCV, 21.8% of the laboratories using different HbA1c methods are not able to distinguish an HbA1c result of 59 mmol/mol (7.5%-DCCT) from a previous HbA1c result of 53 mmol/mol (7.0%-DCCT). It can be presumed that differences in HbA1c results of 5 mmol/mol (0.5%-DCCT) do influence treatment decisions. © Copyright 2011, Mary Ann Liebert, Inc.


Bots M.,University of Amsterdam | Stroobants A.K.,University of Amsterdam | Delzenne B.,University of Amsterdam | Soeters M.R.,University of Amsterdam | And 6 more authors.
Clinical Chemistry and Laboratory Medicine | Year: 2015

Background: Haemoglobin (Hb) variants are well-known factors interfering with accurate HbA1c testing. This report describes two novel Hb variants leading to inappropriate quantification of HbA1c by ion-exchange chromatography. Methods: Glycated forms of novel Hb variants were recognised in the blood of two patients with diabetes mellitus screened by HbA1c ion-exchange chromatography. Dedicated high-resolution cation-exchange chromatography and subsequent DNA sequencing revealed the exact nature of the variants. Other common techniques for quantifying HbA1c were applied on both samples and haematological parameters were determined to judge possible pathology associated with the novel Hb variants. Results: A fraction of 15% of abnormal Hb was observed in a 37-year-old female. DNA sequencing revealed a heterozygous mutation in the α1-globin gene, resulting in a leucine-to-phenylalanine amino-acid substitution (HBA1: c.301C>T, p.Leu101Phe). We named this variant Hb Weesp. The other novel variant, Hb Haelen, presented as a 40% fraction in a 63-year-old male and resulted from a heterozygous amino acid substitution in the β-globin gene (HBB: c.335T>C, p.Val112Gly). The presence of both Hb variants resulted in aberrant separation of the Hb components, leading to an inadequate quantification of HbA1c. Conclusions: Close examination of HbA1c chromatograms revealed two novel, clinically silent Hb variants that interfere with HbA1c quantification. Healthcare providers need to be aware of the potential of such Hb variants when interpreting HbA1c results. © 2015 by De Gruyter.


Speeckaert M.,Ghent University | Van Biesen W.,Ghent University | Delanghe J.,Ghent University | Slingerland R.,Isala Klinieken | And 8 more authors.
Nephrology Dialysis Transplantation | Year: 2014

Background Although measurement of haemoglobin A1c has become the cornerstone for diagnosing diabetes mellitus in routine clinical practice, the role of this biomarker in reflecting long-term glycaemic control in patients with chronic kidney disease has been questioned. Methods Consensus review paper based on narrative literature review. Results As a different association between glycaemic control and morbidity/mortality might be observed in patients with and without renal insufficiency, the European Renal Best Practice, the official guideline body of the European Renal Association-European Dialysis and Transplant Association, presents the current knowledge and evidence of the use of alternative glycaemic markers (glycated albumin, fructosamine, 1,5-anhydroglucitol and continuous glucose monitoring). Conclusion Although reference values of HbA1C might be different in patients with chronic kidney disease, it still remains the cornerstone as follow-up of longer term glycaemic control, as most clinical trials have used it as reference. © 2014 The Author.


Lenters-Westra E.,Dr. Van Heesweg 2 | Lenters-Westra E.,European Reference Laboratory for Glycohemoglobin | Slingerland R.J.,Dr. Van Heesweg 2 | Slingerland R.J.,European Reference Laboratory for Glycohemoglobin
Clinical Chemistry | Year: 2014

BACKGROUND: In 2009, we investigated the conformance of 8 hemoglobin A 1c (Hb A1c) point-of-care (POC) instruments. Since then, instruments have improved and new devices are available on the market. In this second study, we evaluated the performance of DCA Vantage, Afinion, InnovaStar, Quo-Lab, Quo-Test, Cobas B101, and B-analyst Hb A1c POC instruments. METHODS: Clinical and Laboratory Standards Institute protocols EP-5 and EP-9 were applied to investigate imprecision, accuracy, and bias. We assessed bias using the mean of 3 certified secondary reference measurement procedures (SRMPs). Assay conformance with the National Glycohemoglobin Standardization Program (NGSP) certification criteria was also evaluated. Interference of common Hb variants was investigated for methods that could work with hemolysed material. RESULTS: The total CVs for all instruments, except for the DCA Vantage at a high Hb A 1c value, were ≤ 3.1% in SI units and ≤ 2.1% in Diabetes Control and Complications Trial (DCCT) units. Afinion, DCA Vantage, B-analyst, and Cobas B101 instruments passed the NGSP criteria with 2 different reagent lot numbers. Quo-Test, Quo-Lab, and InnovaStar instruments had a negative bias compared to the mean of the 3 SRMPs and failed NGSP criteria. Most of the common Hb variants did not interfere with the investigated instruments, except Hb AE for the Cobas B101. CONCLUSIONS: Afinion, DCA Vantage, Cobas B101, and B-analyst instruments met the generally accepted performance criteria for Hb A 1c. Quo-Test, Quo-Lab, and InnovaStar met the criteria for precision but not for bias. Proficiency testing should be mandated for users of Hb A 1c POC assays to ensure quality. © 2014 American Association for Clinical Chemistry.


Lenters-Westra E.,European Reference Laboratory for Glycohemoglobin | Strunk A.,Isala | Campbell P.,Trinity Biotech | Slingerland R.J.,European Reference Laboratory for Glycohemoglobin
Scandinavian Journal of Clinical and Laboratory Investigation | Year: 2016

Background: Hb-variant interference when reporting HbA1c has been an ongoing challenge since HbA1c was introduced to monitor patients with diabetes mellitus. Most Hb-variants show an abnormal chromatogram when cation-exchange HPLC is used for the determination of HbA1c. Unfortunately, the Tosoh G8 generates what appears to be normal chromatogram in the presence of Hb-Tacoma, yielding a falsely high HbA1c value. The primary aim of the study was to investigate if the Afinion HbA1c point-of-care (POC) instrument could be used as an alternative method for the Tosoh G8 when testing for HbA1c in the presence of Hb-Tacoma. Methods: Whole blood samples were collected in K2EDTA tubes from individuals homozygous for HbA (n = 40) and heterozygous for Hb-Tacoma (n = 20). Samples were then immediately analyzed with the Afinion POC instrument. After analysis, aliquots of each sample were frozen at −80 °C. The frozen samples were shipped on dry ice to the European Reference Laboratory for Glycohemoglobin (ERL) and analyzed with three International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) and National Glycohemoglobin Standardization Program (NGSP) Secondary Reference Measurement Procedures (SRMPs). The Premier Hb9210 was used as the reference method. Results: When compared to the reference method, samples with Hb-Tacoma yielded mean relative differences of 31.8% on the Tosoh G8, 21.5% on the Roche Tina-quant Gen. 2 and 16.8% on the Afinion. Conclusions: The Afinion cannot be used as an alternative method for the Tosoh G8 when testing for HbA1c in the presence of Hb-Tacoma. © 2016 Medisinsk Fysiologisk Forenings Forlag (MFFF)


Lenters-Westra E.,Isala Klinieken | Lenters-Westra E.,European Reference Laboratory for Glycohemoglobin | Slingerland R.J.,Isala Klinieken | Slingerland R.J.,European Reference Laboratory for Glycohemoglobin
Clinical Chemistry | Year: 2010

BACKGROUND: Hemoglobin A1c (Hb A1c) point-of-care (POC) instruments are widely used to provide rapidturnaround results in diabetic care centers. We investigated the conformance of variousHbA 1cPOCinstruments (In2it from Bio-Rad, DCA Vantage from Siemens, Afinion and Nycocard from Axis-Shield, Clover from Infopia, InnovaStar from DiaSys, A1CNow from Bayer, and Quo-Test from Quotient Diagnostics) with generally accepted performance criteria for Hb A1c. METHODS: The CLSI protocols EP-10, EP-5, and EP-9 were applied to investigate imprecision, accuracy, and bias. We assessed bias using 3 certified secondary reference measurement procedures and the mean of the 3 reference methods. Assay conformance with the National Glycohemoglobin Standardization Program (NGSP) certification criteria, as calculated from analyses with 2 different reagent lot numbers for eachHbA1c method, was also evaluated. RESULTS: Because of disappointing EP-10 results, 2 of the 8 manufacturers decided not to continue the evaluation. The total CVs from EP-5 evaluations for the different instruments with a low and high Hb A1c value were: In2it 4.9% and 3.3%, DCA Vantage 1.8% and 3.7%, Clover 4.0% and 3.5%, InnovaStar 3.2% and 3.9%, Nycocard 4.8% and 5.2%, and Afinion 2.4% and 1.8%. Only the Afinion and the DCA Vantage passed the NGSP criteria with 2 different reagent lot numbers. CONCLUSIONS: Only the Afinion and the DCA Vantage met the acceptance criteria of having a total CV <3% in the clinically relevant range. The EP-9 results and the calculations of the NGSP certification showed significant differences in analytical performance between different reagent lot numbers for all Hb A 1c POC instruments. © 2009 American Association for Clinical Chemistry.

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