Diagnosis and classification of diabetes

Diagnostic criteria for diabetes:

WG-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.