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The IFCC Reference Measurement System for HbA_1c: A 6-Year Progress Report

¹ Queen Beatrix Hospital, Winterswijk, The Netherlands (IFCC-network coordinator); ² Norfolk and Norwich University Hospital, and School of Medicine, Health Policy and Practice, UEA, Norwich, UK; ³ Centro Interdipartimentale per la Riferibilità Metrologica in Medicina di Laboratorio (CIRME), Università degli Studi di Milano, Milano, Italy; ⁴ Institute of Biopathological Medicine, Kanagawa, Japan (JDS/JSCC network coordinator); ⁵ University of Missouri School of Medicine, Columbia, MO (NGSP network coordinator); ⁶ Malmoe University Hospital, Malmoe, Sweden (Coordinator Reference System Sweden); ⁷ Austin Pathology, Austin Health, Heidelberg, Australia; ⁸ Isala Klinieken, Zwolle, the Netherlands; ⁹ Center for Disease Control and Prevention, Atlanta, GA; ¹⁰ INSTAND e.V., Duesseldorf, Germany; ¹¹ Brigham and Women’s Hospital and Harvard Medical School, Boston, MA.

^aAddress correspondence to this author at: Queen Beatrix Hospital, Beatrixpark 1, 7101 BN Winterswijk, the Netherlands. Fax +31 543 524265; e-mail c.w.weykamp{at}skbwinterswijk.nl.

Background: The IFCC Reference Measurement System for hemoglobin (Hb)A_1c (IFCC-RM) has been developed within the framework of metrologic traceability and is embedded in a network of 14 reference laboratories. This paper describes the outcome of 12 intercomparison studies (periodic evaluations to control essential elements of the IFCC-RM).

Methods: Each study included: unknown samples (to test individual network laboratories); known samples (controls); recently manufactured calibrators (to check calculated assigned value); stored calibrators (to test stability) and a calibration-set (to calibrate the IFCC-RM). The unknown samples are measured by use of the IFCC-RM and the designated comparison methods [DCMs; the National Glycohemoglobin Standardization Program (NGSP) in the US, Japanese Diabetes Society/Japanese Society for Clinical Chemistry (JDS/JSCC) in Japan, and Mono-S in Sweden] are used to investigate the stability of the Master Equation (ME), the relationship between IFCC-RM and DCMs.

Results: A total of 105 IFCC-RM data sets were evaluated: 95 were approved, 5 were not, and for 5 no data were submitted. Trend analysis of the MEs, expressed as change in percentage HbA_1c per year, revealed 0.000% (NGSP, not significant), –0.030%, (JDS/JSCC; significant) and –0.016% (Mono-S; not significant). Evaluation of long-term performance revealed no systematic change over time; 2 laboratories showed significant bias, 1 poor reproducibility. The mean HbA_1c determined by laboratories performing mass spectrometry (MS) was the same as the mean determined by laboratories using capillary electrophoresis (CE), but the reproducibility at laboratories using CE was better. One batch of new calibrators was not approved. All stored calibrators were stable.

Conclusion: A sound reference system is in place to ensure continuity and stability of the analytical anchor for HbA_1c.

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				A. Geistanger, S. Arends, C. Berding, T. Hoshino, J.-O. Jeppsson, R. Little, C. Siebelder, C. Weykamp, and on behalf of the IFCC Working Group on Standardiza 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 Clin. Chem., August 1, 2008; 54(8): 1379 - 1385. [Abstract] [Full Text] [PDF]