Use of HbA1C for the Diagnosis of Type 2 Diabetes
Use of HbA1C for the Diagnosis of Type 2 Diabetes
The use of HbA1C in the diagnosis of diabetes mellitus
| For the diagnosis of diabetes |
HbA1C >6.5% (48 mmol/mol) HbA1C < 6.5% does not exclude diagnosis by blood glucose Glucose–based tests (FPG, OGTT) are still valid |
| Interpretation of HbA1C < 6.5% |
No recommendation because of insufficient evidence |
| Requirements to fulfil (provisos) for use of HbA1C for diagnosis |
Stringent quality assurance tests in placea Assays standardised to criteria aligned with international reference valuesb Low cost and wide availability No conditions present which preclude accurate measurement (see Table III below) |
| Choice between HbA1C and plasma glucose should be based on local considerations |
Cost Availability of equipment National quality-assurance system Population characteristics (e.g. prevalence of malaria or haemoglobinopathies) Crucial to ensure that accurate blood glucose measurement be generally available at primary healthcare level before introducing HbA1C measurement as a diagnostic tool |
a Appropriate conditions for assay method: Standardised assay; Low coefficient of variability; Calibrated against International Federation of Clinical Chemists (IFCC) standards
b DCCT aligned and NGSP certified
Factors which influence HbA1C measurement
| Erythropoiesis |
Increased HbA1C | Iron deficiency, vitamin B12 deficiency, decreased erythropoiesis |
| Decreased HbA1C | Administration of erythropoietin, iron or vitamin B12, reticulocytosis, chronic liver disease | |
| Altered haemoglobin |
Variable HbA1C | Genetic or chemical alterations in haemoglobin may increase or decrease HbA1C: Haemoglobinopathies, HbF, methaemoglobin |
| Glycation |
Increased HbA1C | Alcoholism, chronic renal failure, decreased intra-erythrocyte pH |
| Decreased HbA1C | Aspirin, vitamins C and E, certain haemoglobinopathies, increased intra-erythrocyte pH | |
| Variable HbA1C | Genetic determinants | |
| Erythrocyte destruction |
Increased HbA1C | With increased erythrocyte life span: Splenectomy |
| Decreased HbA1C | With decreased erythrocyte life span: Haemoglobinopathies, splenomegaly,rheumatoid arthritis, drugs (e.g. antiretrovirals, ribavirin, dapsone) | |
| Assays |
Increased HbA1C | Hyperbilirubinaemia, carbamylated haemoglobin, alcoholism, large doses of aspirin, chronic opiate use |
| Decreased HbA1C | Hypertriglyceridaemia | |
| Variable HbA1C | Haemoglobinopathies | |
Note: Some of these factors cannot be detected by certain assays |
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Reference
1.World Health Organisation. Use of glycated haemoglobin (HbA1C) in the diagnosis of diabetes mellitus: http://www.who.int/diabetes/publications/reporhba1c_2011.pdf. (accessed 25 January 2016).