Hba1c for diagnosis Dr Karen Adamson

What is HbA1c? • Glucose binds irreversibly to haemoglobin in red blood cells, forming HbA1c • The higher the glucose, the higher the HbA1c • HbA1c reflects the prevailing blood glucose over the preceding 2-3 months

Why Measure HbA1c? • Serial measures show how an individual’s glucose control, and thus risk of complications, change in response to alterations in management • Measure 2-6 monthly • Set individual target levels

HbA1c as an Indicator of Glycaemic Control

Available Measures of Glycaemic Control Fasting Plasma Glucose (FPG)* Preferred test for diagnosis (mmol/l or mg/dL) Snapshot of glycaemia Oral Glucose Tolerance Test (OGTT) Response to glucose challenge, can be used to diagnose disease HbA1c (Glycated Haemoglobin) Long-term measurement of glycaemic control (~3 months) Postprandial Glucose (PPG) Glucose level after eating (mmol/l or mg/dL)** Random Blood Glucose (RBG) Measures blood sugar at any point in time, normal levels not defined Continuous Glucose Monitoring (CGM) Assesses how blood glucose levels react to insulin, exercise and meals There are several measures for glycaemic control. Fasting Plasma Glucose (FPG) Oral Glucose Tolerance Test (OGTT) HbA1c (Glycosylated Haemoglobin) Postprandial Glucose (PPG) Random Blood Glucose (RBG) Continuous Glucose Monitoring (CGM) *measured after at least 8 hours of fasting; **measured 1- 2 hours after eating

Not suitable for HbA1C Rapid onset of diabetes Suspected T1DM – see symptomatic patient flowchart Drug-induced: steroids, anti-psychotics, immunosuppressants – a fasting glucose may not be sufficient. Seek advice from diabetes team. Pancreatic disease. Seek advice from diabetes team. Pregnancy – HbA1C reduced in pregnancy. Gestational diabetes should be diagnosed by OGTT. N.B. OGTT diagnostic criteria are lower than for the general population. Conditions affecting Hb turnover / HbA1C assay Haemoglobinopathy Haemolytic anaemia Severe blood loss, Blood transfusion Splenomegaly / Splenectomy Renal dialysis +/- erythropoitein Anti-retrovirals, ribavarin, dapsone

+ = DIABETES Diagnosis of diabetes mellitus in symptomatic patients Thirst, polyuria Unexpected weight loss Symptomatic patient Recurrent infection Blurring of vision Discoloured/ulcerated feet + random glucose ≥11.1 mmol/L or fasting glucose ≥7.0 mmol/L = DIABETES Mild symptoms Severe symptoms ?ketotic vomiting / dehydration URGENT HOSPITAL ADMISSION Full assessment & initiate management of Type 2 Diabetes young age ketonuria (or ketonaemia*) OR URGENT discussion with diabetes team (may need insulin therapy) *ketones can be measured on some POC glucometers

All glucose measurements used for diagnosis must be laboratory samples Diagnosis of diabetes mellitus in asymptomatic patients not diabetic (repeat on separate day) ≤6.0 mmol/L random glucose ≥11.1 mmol/L repeat fasting glucose high risk Consider HbA1C 6.1 – 6.9 mmol/L fasting glucose INITIAL lab glucose ≥7.0 mmol/L diabetes ≥7.0 mmol/L (random OR fasting) 7.8 – 11.0 mmol/L 6.1 – 6.9 mmol/L random glucose fasting suitable for HbA1C? * YES NO (repeat blood test on a separate day) HbA1C OGTT not diabetic high risk not diabetic high risk diabetes diabetes ≤41 mmol/mol 42 – 47 mmol/mol ≥48 mmol/mol fasting glucose ≤6.0 6.1 – 6.9 ≥ 7.0 mmol/L AND OR OR All glucose measurements used for diagnosis must be laboratory samples 2-hr glucose ≤7.7 7.8 – 11.0 ≥ 11.1 mmol/L