2011 Consensus Meeting on the Worldwide Standardization of Hemoglobin A1c Measurement

Abstract

The measurement of hemoglobin A1c (Hb A1c)2 is integral to the management of patients with diabetes. Hb A1c is used in the evaluation of long-term (8–12 weeks) glucose control, to alter therapy and predict the risk for development of microvascular complications, and as a criterion to diagnose diabetes. Early Hb A1c assays measured different forms of glycohemoglobin and lacked standardization. The publication of the Diabetes Control and Complications Trial (DCCT) in 1993 motivated the development of standardization programs in Japan, Sweden, and the US. The National Glycohemoglobin Standardization Program (official name later shortened to the acronym NGSP) was by far the most widely implemented program around the world, being used in the vast majority of countries that had Hb A1c standardization. The subsequent development of a reference measurement system by the IFCC led to several meetings to effect universal standardization of Hb A1c. At the initial meeting in 2004, participants reached consensus for the adoption of the IFCC reference method as the global standard for calibration of Hb A1c assays. All participants agreed that the same Hb A1c values should be reported globally. These decisions were endorsed at subsequent meetings in 2007 and 2009. Additional recommendations, published in 2010 in Clinical Chemistry (1), were: Hb A1c results should be reported by clinical laboratories worldwide in Système International (SI) units (mmol/mol, no decimals) and derived NGSP units (%, 1 decimal), using the IFCC–NGSP master equation (DCCT units). Hb A1c conversion tables including both SI (IFCC) and NGSP units should be easily accessible to the diabetes community. Editors of journals were strongly recommended to require that submitted manuscripts report Hb A1c in both SI (IFCC) and NGSP/DCCT units. The most recent meeting was held in December 2011 in Dubai. The objective of the deliberation was to evaluate the progress of implementation of the prior recommendations. Unfortunately, the goal of reporting the same units worldwide has not been realized. Dual reporting has been adopted by very few countries and has been transitory for the vast majority of these countries. Some countries have elected to report only SI units, while other countries have decided to maintain NGSP/DCCT units. Notwithstanding these developments, the meeting attendees recommended that both SI (IFCC) and NGSP/DCCT units be used for reporting Hb A1c in journals and other printed materials. To facilitate this goal, calculators to convert between millimoles per mole and percentage have been made available (http://www.hba1c.nu/eng2.html and http://www.ngsp.org/convert1.asp). Several journals have adopted this policy and all journals are encouraged to do so. American Diabetes Association: Sue Kirkman and Matt Petersen. European Association for the Study of Diabetes: Viktor Joergens and Andrew Boulton. International Diabetes Federation: Jean-Claude Mbanya and Stephen Colagiuri. IFCC: Garry John and Graham Beastall. International Society for Pediatrics and Adolescent Diabetes: Ragnar Hanas and Lynda Fisher. Japanese Diabetes Society: Izumi Takei. NGSP: David Sacks. hemoglobin A1c Diabetes Control and Complications Trial National Glycohemoglobin Standardization Program Système International. Work in the author's laboratory is funded by the Intramural Research Program of the National Institutes of Health.