The sugar in your blood is called glucose. Most monosaccharides, including glucose, galactose, and fructose, spontaneously (i.e. non-enzymatically) bond with hemoglobin, when present in the bloodstream of humans
When glucose builds up in your blood, it binds to the hemoglobin in your red blood cells. The A1c test measures how much glucose is bound and called Glycated hemoglobin (glycohemoglobin, hemoglobinA1c, HbA1c, less commonly HbA1c, HgbA1c, Hb1c, etc., also A1C
Red blood cells live for about 3 months, so they test the average level of glucose in your blood for the past 3 months. If your glucose levels have been high over recent weeks, your hemoglobin A1c test will be higher
It has a strong predictive value for Diabetes mellitus complications. Two large-scale studies – the UK Prospective Diabetes Study (UKPDS) and the Diabetes Control and Complications Trial (DCCT) – demonstrated that improving HbA1c by 1% (or 11 mmol/mol) for people with type 1 diabetes or type 2 diabetes cuts the risk of microvascular complications by 25%.
Microvascular complications include Retinopathy, Neuropathy, and Diabetic nephropathy (kidney disease) . Research has also shown that people with type 2 diabetes who reduce their HbA1c level by 1% are 19% less likely to suffer cataracts 16% less likely to suffer heart failure 43% less likely to suffer amputation or death due to peripheral vascular disease
The frequency of testing may vary depending on individual clinical situation and treatment regimen used and physician judgement.
It should be performed at least 2/year in patients who are meeting treatment goals and who have stable glucose control and should be done 4 /year of patients whose therapy has been changed or those not reaching glycemic goals.
The advantage of the test is It is not a fasting test. You can take it any time of day, before or after eating. To measure a person’s HbA1c level, a blood sample is taken from the patient’s arm and used to produce a reading. In some cases, such as with HbA1c testing for children, a single droplet of blood may only be required to find out how much haemoglobin A1c is present. HbA1c level of more than 6.5% performed in a laboratory using national glycohemoglobin standardization program (NGSP) certified method and standardized to Diabetes Control and Complication trial assay (DCCT) assay.
May be affected by conditions that affect erythrocyte turnover (hemolysis, blood loss,blood transfusion or hemoglobinopathy ), supplements such as vitamins C and E and high cholesterol levels, Kidney disease and liver disease may also affect the test.
Patient with HBA1c 6-6.5% has a 5-year risk for developing Diabetes Mellitus. Prediabetic condition is defined for HbA1c 5.7%-6.4 % range.
The glycemic goals have been defined for tracking HBA1c is individualized based on the duration of diabetes mellitus, age/life expectancy, comorbid conditions (Cerebrovascular disease) or advanced microvascular complications, hypoglycemia unawareness, and individual patient preference.
Goal of <8% may be allowed for patients with a history of severe hypoglycemia, limited life expectancy, advanced microvascular or macrovascular complications, extensive comorbid conditions, and those with long-standing Diabetes Mellitus who did not reach the target glucose level despite treatment and appropriate monitoring.
Goal of <7 % have shown to reduce microvascular and neuropathic complications of Diabetes Mellitus and is associated with a long-term decrease in macrovascular disease.
Goal of HbA1c <6.5% may be advised in patients with Diabetes Mellitus of shorter duration, with long life expectancy, and no significant Cerebrovascular Disease, given that it can be achieved without hypoglycemia.
Results of HbA1c help in intensification of the Diabetes Mellitus therapy and improvement in glycemic control when used in POCT (Point of care testing) to manage and prevent microvascular and macrovascular complications however It does not capture glycemic variability or hypoglycemia.