World-Wide Standards for Glucose Test Coming Soon

The proposed new procedure based, for the first time, on reference materials would result in lower HbA1c percentage values than clinicians are used to seeing because of the higher specificity of the method, the statement warned. 

Thus, hemoglobin A1c levels will need to be reported as both the percentages typically used in the U.S. under the National Glycohemoglobin Standardization Program (NGSP) and in the SI units of mmol/mol under the new International Federation of Clinical Chemistry (IFCC) scheme.

These conclusions represented a consensus among the American Diabetes Association, the European Association for the Study of Diabetes, the International Diabetes Federation, the IFCC, and the International Society for Pediatric and Adolescent Diabetes.

Point of care HbA1c systems need to be part of the quality control changes along with the laboratories, noted statement authors Ragnar Hanas, MD, PhD, of Uddevalla Hospital in Uddevalla, Sweden, and Garry John, PhD, of the Norfolk and Norwich University Hospital in Norwich, England.

Standardization has been sought as far back as 1984 but became an international issue only with publication of the DCCT trial in 1993, Hanas and John wrote in the consensus statement simultaneously published in Diabetes Care and several other diabetes and clinical chemistry journals.

The U.S. subsequently developed the current system using the DCCT method as the primary reference method whereas Japan and Sweden developed their own standardization programs with different calibration methods.

But all those systems lack primary and secondary reference materials that ensure that a patient would have comparable results from any laboratory, Hanas and John explained.

The new IFCC procedure was created to remedy this problem. It includes:

• A specific incubation process to quantify and separate glycosylated and non-glycosylated hexapeptides on the hemoglobin molecule using mass spectrometry or capillary electrophoresis.
• Isolation of pure HbA1c and pure non-glycosylated hemoglobin from human blood and mixed in well-defined proportions to produce a certified primary reference material set for calibrating the primary reference measurement system.
• Assigning primary reference measurement system values to secondary reference materials -- whole blood -- then used by the manufacturers to calibrate their instruments.

Implementation of this method is ongoing, with a laboratory network established to put the new system into practice and maintain it, according to the statement.

This reference system "represents the only valid anchor to implement standardization," but determining how to present the numbers has been the subject of considerable debate, the consensus statement authors wrote.

A master equation was thus developed to derive NGSP percentage units from the IFCC mmol/mol units.

Conversion tables should be made easily accessible to the diabetes community, based on a consensus meeting held late last year between the diabetes associations and medical journal editors.

Hanas R, John G "2010 Consensus Statement on the Worldwide Standardisation of the Haemoglobin A1c Measurement" Diabetes Care 2010.