Today, approximately 420 million people in the world have diabetes, a chronic disease that occurs in the two main types when the pancreas is no longer able to make insulin (Type 1 diabetes), or when the body cannot make good use of the insulin it produces (Type 2 diabetes). Caused by lifestyle related obesity, Type 2 diabetes accounts for at least 90% of all cases of diabetes and is growing rapidly.
Combined efforts by The World Health Organization (WHO) and the International Diabetes Federation (IDF) have endeavoured to standardize criteria for the diagnosis and management of diabetes. A vital component of this work is the standardization of mass-produced blood tests used in examining diabetes.
Since 2002 the International Bureau Weights and Mesures (BIPM), the International Federation for Clinical Chemistry and Laboratory Medicine (IFCC), and the International Laboratory Accreditation Cooperation (ILAC) have collaborated through the Joint Committee for Traceability in Laboratory Medicin (JCTLM) to establish accurate results for patient care.
International diagnostic criteria require that all methods for measuring glucose in whole blood or blood plasma should produce the same results. This was achieved as long ago as 1982 when an international reference method was established, and all manufacturers standardize their laboratory methods against this reference.
The most common use of glucose measurement today is in home testing to monitor the effectiveness of treatment for diabetes. Many methods are available, and all are linked to the 1982 reference method. However, not all methods give identical results and ongoing activity is improving the situation.
Haemoglobin A1c measurement
The measurement of Haemoglobin A1c* is the second most widely performed blood test in people with diabetes. The A1c form of haemoglobin can bind glucose molecules in a process known as glycosylation. So, in untreated diabetes the percentage of HbA1c in the blood is much higher than in non-diabetic people.
Prior to 2000, results differed in the methods available making international cooperation in managing diabetes difficult. Following the publication of a novel reference method in 2004, IDF, WHO and other health organizations required all manufacturers of HbA1c methods to align to the reference method.
The quality of HbA1c methods improved dramatically benefitting both patients and research. As a result, in 2011, the WHO recommended the use of HbA1c in preference to glucose for the diagnosis of diabetes.
Today all laboratory-based methods for HbA1c produce the same results while the variability of near patient testing methods is diminishing.
Insulin C-peptide measurement
Surprisingly perhaps, the measurement of insulin has no role in the routine diagnosis and management of diabetes. However, insulin C-peptide does have a specialized role. When the pancreas makes insulin the two chains of the native hormone (A and B) are linked by the C-peptide, which is cleaved off before insulin becomes active. There is no C-peptide in the synthetic forms of insulin used to treat diabetes. Therefore, the measurement of C-peptide is an indicator of natural insulin secretion even in the presence of administered synthetic insulin. Standardization methods for C-peptide measurement are now at an advanced stage.
JCTLM improving health care for persons with diabetes
The JCTLM works with a range of stakeholders to facilitate better agreement between laboratory medicine methods. The JCTLM manages a global database of reference methods and materials across laboratory medicine, including methods and materials for glucose, HbA1c and C-peptide measurement.
*HbA1c, sometimes called A1c in the United States