DIABETES MELLITUS : DEFINITIONS AND DIAGNOSIS

DIABETES MELLITUS

DEFINITIONS AND DIAGNOSIS

Diabetes is a group of metabolic disease characterized by hyperglycemia resulting from defect in insulin secretion, insulin action or both. The prevalence of diabetes worldwide is anticipated to rise to 5.4% by the year 2025 and most of them will be of developing countries. The diagnosis depends solely on the demonstration of hyperglycemia.

Hyperglycemia seen in diabetes is mainly due to increased hepatic output of glucose and decreased uptake of glucose by skeletal muscle and store as glycogen. These conditions occurs due to

i.                    β-cell dysfunction

ii.                  Insulin resistance

iii.                Abnormalities of insulin independent glucose clearance.

Following the WHO first Expert Committee Report published in 1965, the National Diabetes Data Group (NDDG) in 1979 defined diabetes in adults according to 1 of the 3 following criteria.

1.  Presence of classical sign and symptoms of polyuria, polydipsia, weight loss and ketonuria.

2.      FPG ≥140 mg/dl on more than one occasion or

3.   A 2 hour glucose level ≥200 mg/dl and 1 value between 0 and 2 hours, on more than one occasion after a 75 gram oral glucose tolerance test.

It also defined glucose intolerance. It should meet 3 criteria

1.      FPG <140 mg/dl

2.      2 hour glucose level 140-199 mg/dl after OGTT

3.      At least 1 glucose level ≥200 mg/dl at 30, 60 and 90 minutes after OGTT.

In 1979 classification scheme recognized two major forms of diabetes: type I (insulin dependent) diabetes mellitus (IDDM) and type II (non-insulin dependent) diabetes mellitus (NIDDM). Later classification was based on etiology and termed type 1 and type 2 diabetes in 1997. 

According to WHO in 1980

Glucose intolerance: 2 hour post load glucose value between 140-199 mg/dl if FPG was less than 140 mg/dl, 2 criteria instead of 3.

It defined diabetes as FPG ≥140 mg/dl plus presence of sign and symptoms or random glucose level ≥200 mg/dl and 2 hour post load level ≥200 mg/dl

The Expert committee on the Diagnosis and Classification of Diabetes Mellitus in 1997 and the WHO in 1998 recommended – Any one of the following is diagnostic and if positive confirm by repeat testing on subsequent day.

1.    FPG ≥126 mg/dl, (≥110 mg/dl for venous whole blood) Fasting means no caloric intake for at least 8 hours.

2.      Presence of sign and symptoms polyuria, polydipsia and unexplained weight loss. or

3.      The 2 hour glucose ≥200 mg/dl (≥180 mg/dl for venous whole blood) after OGTT

4.      Random plasma glucose level ≥200 mg/dl

Here the FPG was reduced from 140 mg/dL to 126 mg/dL to better identify individuals at risk of retinopathy and nephropathy.

IGT according to this was – Both criteria should be met.

1.   2 hour glucose level 140-199 mg/dl (120-179 mg/dl for venous whole blood) after 75 g OGTT and FPG <110 mg/dl

Impaired Fasting glucose (IFG)

1.      FPG 110-125 mg/dl (100-110 mg/dl for venous whole blood).