Note that where there is a Gestational diabetes mellitus (GDM) or Previous GDM (i.e. permissible values 3 & 5) and a current history of Type 2 diabetes then record 'Code 2' Type 2 diabetes.

This same principle applies where a history of either Impaired fasting glycaemia (IFG) or Impaired glucose tolerance (IGT) and a current history and Type 2 diabetes, then record 'Code 2' Type 2 diabetes.

CODE 01     Type 1 diabetes

Beta-cell destruction, usually leading to absolute insulin deficiency. Includes those cases attributed to an autoimmune process, as well as those with beta-cell destruction and who are prone to ketoacidosis for which neither an aetiology nor pathogenesis is known (idiopathic). It does not include those forms of beta-cell destruction or failure to which specific causes can be assigned (e.g. cystic fibrosis, mitochondrial defects). Some subjects with Type 1 diabetes can be identified at earlier clinical stages than 'diabetes mellitus'.

CODE 02     Type 2 diabetes

Type 2 includes the common major form of diabetes, which results from defect(s) in insulin secretion, almost always with a major contribution from insulin resistance.

CODE 03     Gestational diabetes mellitus (GDM)

GDM is a carbohydrate intolerance resulting in hyperglycaemia of variable severity with onset or first recognition during pregnancy. The definition applies irrespective of whether or not insulin is used for treatment or the condition persists after pregnancy. Diagnosis is to be based on the Australian Diabetes in Pregnancy Society (ADIPS) Guidelines.

CODE 04     Other (secondary diabetes)

This categorisation includes less common causes of diabetes mellitus, but are those in which the underlying defect or disease process can be identified in a relatively specific manner. They include, for example, genetic defects of beta-cell function, genetic defects in insulin action, diseases of the exocrine pancreas, endocrinopathies, drug or chemical-induced, infections, uncommon forms of immune-mediated diabetes, other genetic syndromes sometimes associated with diabetes.

CODE 05     Previous GDM

Where the person has a history of GDM.

CODE 06     Impaired fasting glycaemia (IFG)

IFG or 'non-diabetic fasting hyperglycaemia' refers to fasting glucose concentrations, which are lower than those required to diagnose diabetes mellitus but higher than the normal reference range. An individual is considered to have IFG if they have a fasting plasma glucose of 6.1 or greater and less than 7.0 mmol/L if challenged with an oral glucose load, they have a fasting plasma glucose concentration of 6.1 mmol/L or greater, but less than 7.0 mmol/L, AND the 2 hour value in the Oral Glucose Tolerance Test (OGTT) is less than 7.8 mmol/L.

CODE 07     Impaired glucose tolerance (IGT)

IGT is categorised as a stage in the natural history of disordered carbohydrate metabolism; subjects with IGT have an increased risk of progressing to diabetes. IGT refers to a metabolic state intermediate between normal glucose homeostasis and diabetes. Those individuals with IGT manifest glucose intolerance only when challenged with an oral glucose load. IGT is diagnosed if the 2 hour value in the OGTT is greater than 7.8 mmol/L. and less than 11.1 mmol/L AND the fasting plasma glucose concentration is less than 7.0 mmol/L.

CODE 08     Not diagnosed with diabetes

The subject has no known diagnosis of Type 1, Type 2, GDM, Previous GDM, IFG, IGT or Other (secondary diabetes).

CODE 09     Not assessed

The subject has not had their diabetes status assessed.

CODE 99     Not stated/inadequately described

This code is for unknown or information unavailable.

The diagnosis is derived from and must be substantiated by clinical documentation.

Developed based on Definition, Diagnosis and Classification of Diabetes Mellitus and its Complications Part 1: Diagnosis and Classifications of Diabetes Mellitus Provisional Report of a World Health Organization Consultation (Alberti & Zimmet 1998).