An innovative test for diagnosing diabetes
14 January, 2011 ¦ Geneva -- A new test for diagnosing diabetes mellitus has been accepted by a WHO-backed group of experts, offering a more practical approach to test for the disease that affects over 220 million people worldwide.
A report on a WHO expert consultation issued today on the diagnosis of diabetes recommends the acceptability of glycated haemoglobin, or HbA1c, as an additional test to diagnose this debilitating and deadly disease.
Dr Ala Alwan, Assistant Director General of WHO's Noncommunicable Diseases and Mental Health Cluster, says the addition of a new test for diagnosing diabetes is a positive development, provided that stringent quality assurance tests are in place, measurements standardized and no conditions precluding HbA1c's accurate measurement.
"Testing HbA1c is a practical way of diagnosing diabetes," says Dr Alwan. "Unlike other means of diagnosis, it does not require a patient to fast before a blood sample is taken, nor to consume a glucose drink that many people find unpalatable. HbA1c also has the advantage of reflecting the person's average blood glucose levels over the preceding 2-3 months."
"But its higher cost in comparison to other diagnostic tools will, for now, make it harder for developing countries to use. It also remains unreliable in medical conditions with rapid red cell turnover, such as haemolytic or iron deficiency anaemias. So the priority for low-income countries will continue to be ensuring the availability of blood glucose measurement at the primary health care level before widely introducing HbA1c for diagnosing diabetes.”
Many people with the more common type 2 diabetes exhibit no symptoms. Diagnosis has long been based on measuring glucose values in a blood sample taken while fasting for 8-14 hours before the sample is taken, or after taking a glucose drink. Research has been ongoing for tests that would avoid the day-to-day variability of blood glucose values.
HbA1c, a type of the red blood cell protein haemoglobin, forms when red cells are exposed to glucose in the plasma. It has been widely used since the 1980s as an indicator of how well glycaemia was being controlled in people with diabetes.
Several studies had shown that HbA1c can also be used to diagnose diabetes from a blood sample, but before now it had not been recommended as a diagnostic test for several reasons. For example, there had been no standard method for measuring HbA1c. Other factors were the test’s, or assay’s, relatively high cost, as well as its unreliability when used in patients who have certain forms of anaemia, or genetic defects known as haemoglobinopathies, such as the sickle cell trait.
But with recent technological advances, HbA1c assays are becoming highly standardized and most are not affected by haemoglobinopathies. The assay, however, is still not well standardized in many countries, particularly developing ones.
Diabetes kills more than 1 million people annually, almost 80% of which occur in low- and middle-income countries. Almost half of diabetes deaths occur in people aged under 70 years; 55% of diabetes deaths are in women. WHO projects diabetes deaths will double between 2005 and 2030. Healthy diet, regular physical activity, maintaining a normal body weight and avoiding tobacco use can prevent or delay the onset of type 2 diabetes.
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