HbA1c measures glycation of hemoglobin and considered equivalent to mean blood glucose over period of 8 to 12 weeks.
It depends on :
- Red cell turnover
- HbA1c in reticulocytes
- Rate of glycation which depends on age of RBCs
Any factor which cause reduced life span of RBCs may give erroneously low hba1c and vice versa .
Conditions causing high HbA1c
- Iron deficiency anemia
- Pernicious anemia
- Drugs - statins,Aspirin in high doses
- Hyperbilirubinemia
- Renal failure
- Few Hemoglobinopathies
- Splenectomy
Conditions causing low HbA1c
- Hemolytic anemia
- Renal failure
- Hemoglobinopathies
- Splenomegaly
- Drugs - hydroxyurea, Administration of iron and b12, Vitamin c & e ~ antioxidants, TMP-SMX, antiretroviral
- Alcoholism
- Chronic liver disease
- Hypertriglyceridemia
Alternatives for glycated hemoglobin HbA1c are
glycated albumin, fructosamine, or serum albumin-adjusted fructosamine.
Studies done on HbA1c
- NHANES Study
- DETECT 2
- ADAG STUDY
- DCCT
- UKPDS
The A1C test should be performed using a method that is certified by the NGSP (www.ngsp.org)
Criteria for Diabetes
A1C ≥6.5%(48mmol/mol).The test should be performed in a laboratory using a method that is NGSP certified and standardized to the DCCT assay.*
Criteria for Pre Diabetes (ADA 2017)
Reference
- American Diabetes Association Standards of Medical Care in Diabetes 2017
- Use of Glycated Haemoglobin (HbA1c) in the Diagnosis of Diabetes Mellitus Abbreviated Report of a WHO Consultation - 2011