Hba1c for diagnosis Dr Karen Adamson

β-chain α-chain Glucose bound to N-terminal valine of β-chain

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

What Are The Limitations of HbA1c Measurement? Abnormal red cell turnover Abnormal haemoglobin Renal disease Liver disease Pregnancy – HbA1c falls by ~0.5 %

HbA 1c 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 – HbA 1c (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 *measured after at least 8 hours of fasting; **measured 1- 2 hours after eating

Not suitable for HbA 1C 1)Rapid onset of diabetes a)Suspected T1DM – see symptomatic patient flowchart b)Drug-induced: steroids, anti-psychotics, immunosuppressants – a fasting glucose may not be sufficient. Seek advice from diabetes team. c)Pancreatic disease. Seek advice from diabetes team. 2)Pregnancy – HbA1C reduced in pregnancy. Gestational diabetes should be diagnosed by OGTT. N.B. OGTT diagnostic criteria are lower than for the general population. 3)Conditions affecting Hb turnover / HbA1C assay a)Haemoglobinopathy b)Haemolytic anaemia c)Severe blood loss, Blood transfusion d)Splenomegaly / Splenectomy e)Renal dialysis +/- erythropoitein f)Anti-retrovirals, ribavarin, dapsone

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

suitable for HbA 1C ? * YESNO HbA 1C OGTT not diabetic high risk diabetes ≥48 mmol/mol 42 – 47 mmol/mol ≤41 mmol/mol not diabetic high risk diabetes fasting glucose ≤6.0 2-hr glucose mmol/L ≤7.7 ANDOR 6.1 – – 11.0≥ 11.1 ≥ 7.0 All glucose measurements used for diagnosis must be laboratory samples Diagnosis of diabetes mellitus in asymptomatic patients random glucose fasting glucose ≥7.0 mmol/L ≥11.1 mmol/L not diabetic high risk diabetes ≥7.0 mmol/L 6.1 – 6.9 mmol/L ≤6.0 mmol/L INITIAL lab glucose 7.8 – 11.0 mmol/L 6.1 – 6.9 mmol/L random glucose fasting glucose repeat fasting glucose (repeat blood test on a separate day) Consider HbA 1C (repeat on separate day) (random OR fasting)