Diagnosis and classification of diabetes

Diagnostic et classification du diabète

Diagnostic criteria for diabetes:

Diagnosis and classification of diabetesWG-WHO *, 1998 (2011)

The subject has symptoms of diabetes (polyuria, polydipsia, unexplained weight loss) and random blood glucose ≥ 11.1 mmol / l (2.00 g / l);

– Fasting blood glucose (no caloric intake for at least 8 h) is ≥ 7.0 mmol / l (1.26 g / l); 
– Or, glycemia is ≥ 11.1 mmol / l (2.00 g / l) two hours after ingestion of glucose (75 g) during an OGTT.

– Or an HbA1c ≥ 6.5% by a validated method.

The glucose regulation abnormality includes moderate fasting hyperglycemia (IFG) and glucose intolerance (GI).

Moderate fasting hyperglycemia

(IFG) is de ned when:

The fasting blood glucose is ≥ 6.1 mmol / l (1.10 g / l) and <7.0 mmol / l (1.26 g / l).

Glucose intolerance (GI) is defined when:

The fasting blood glucose is <7.0 mmol / l (1.26 g / l), and blood glucose, 120 min after ingestion of glucose (75 g) is ≥ 7.8 mmol / l (1.40 g / L) and <11.1 mmol / l (2.00).

Diagnostic tests:

1- Glycemia:

The threshold values ​​for the diagnosis of diabetes mellitus are chosen so as to separate subjects at significantly increased risk from certain complications specifically caused by diabetes (ie microangiopathies) in subjects without any particular risk.

These threshold values ​​are quite close to the best statistical estimates of the values ​​separating the two distribution curves underlying the bimodal distribution of plasma glucose concentrations.

The diagnosis of diabetes depends in part on the type of test performed (fasting glucose or PGHT).

The reproducibility of fasting blood glucose is much higher than that of blood glucose at 2 h in an HGPO (~ 6% vs ~ 17%). As a result, a significant number of subjects are sometimes reclassified when they are given a PGT.

The 2-hour blood glucose level in PGTT frequently gives a higher prevalence of diabetes than fasting blood glucose.

Blood glucose at 2 h is a better predictor of morbidity / cardiovascular mortality than fasting blood glucose.

Despite its limitations, the HGPO test remains an indispensable tool for the diagnosis of clinically significant abnormalities of glucose metabolism.

2- Peptide C:

Clinical peptide-C assay is particularly useful in some young diabetic patients for classifying and predicting insulin requirements.

The fastest and most convenient application is the simplified glucagon test.

In the fasting morning, a basal blood sample is taken to measure the peptide-C reference level. An iv injection of glucagon (1 mg) is then carried out and, 6 minutes later, another assay of the C-peptide.

A rate of> 0.6 nmol / l (or 1.8 ng / ml) at 6 minutes is sensitive and specific for predicting the absence of insulin requirements for one year for both Type 1 and Type 2 diabetics.

In addition, the same threshold value can be used to select, among Type 2 diabetics on insulin, those who can stop insulin safely and replace insulin therapy with other forms of treatment.

3- Antibody:

Antibodies of major clinical interest in Type 1 diabetes are:

– Antibodies directed against islet cells of Langerhans (ICA).

– Anti-insulin autoantibodies (AI)

– Anti-glutamic acid decarboxylase (GAD).

Anti-IA-2 (protein of cells having homology with the family of tyrosine phosphatase).

– ZNT8: anti-zinc carrier antibody.

– ICAs, IAAs and anti-GAD and anti-IA-2 antibodies are detectable in most Type 1 diabetics, especially during the preclinical and early clinical stages of diabetes, and are the main evidence of the immune process leading to To the destruction of β cells in a given patient.


WG-WHO, 1998

Associated forms / defects


Type 1 Diabetes

Destruction of ß-cells, leading generally to an absolute deficiency in insulin, autoimmune and Idiopathic.

Type 2 diabetes

Can go from a predominant insulin resistance, 
With insulin deficiency related to a predominant defect of secretion, with or without insulin resistance.

Genetic defects altering β-cell function

Chromosome 20, HNF-4 α (ex-MODY 1)

Chromosome 7, glucokinase (MODY 2)

Chromosome 12, HNF-1α (ex-MODY 3)

Chromosome 13, IPF-1 (MODY 4)

Mutation of mitochondrial DNA

Genetic defects altering the action of insulin

Type A insulin resistance

Preaching (Donohue’s syndrome)

Rabson-Mendenhall Syndrome

Lipo-atrophic diabetes

Diseases of the pancreas

Diseases of the exocrine pancreas

Fibro-calcular pancreatopathy


Trauma / pancreatectomy


Cushing’s syndrome






Pharmaco – or chemo-induced

Nicotinic acid


Thyroid hormones







Interferon α


Congenital rubellacytomegalovirus

Rare forms of autoimmune diabetes

Syndrome of the “stiff man”

Anti-insulin receptor antibodies

Other genetic syndromes sometimes associated with diabetes

Trisomy 21

Friedreich’s Disease

Huntington Chorea

Klinefelter Syndrome

Laurence-Moon-Bardet-Biedl syndrome

Dystrophic myotonia (Steinert’s disease)


Prader-Labhart-Willi Syndrome

Turner’s Syndrome

Wolfram Syndrome

Other forms


Cystic fibrosis


Gestational Diabetes

Discovered during pregnancy

PS: The diabetes with ketosis beginning of the African subject is unclassified.

The Metabolic Syndrome:

• There are several definitions of the metabolic syndrome, the choice is based on that of the IDF (International Diabetes Federation) which is based on simple criteria.

Definition of Metabolic Syndrome according to the IDF:


Waist + 2 of 4 other criteria

High waist

Indispensable, with ethno-centered thresholds European origin: ≥ 94 cm / men, ≥ 80 cm / women.

TG high

> 1.5 g / l or treatment

Low HDLc

<0.40 g / l: male, <0.50 g / l: women

PA high

PAS ≥ 130 mmHg and / or PAD ≥ 90 mm Hg or treatment

Fasting fasting glucose

≥ 1 g / l or treatment

TG: triglycerides, PA: blood pressure