Screening Tests for Diabetes Mellitus.

Screening Tests for Diabetes Mellitus.

The screening tests for diabetes include urine and blood glucose examinations.

1. Urine glucose 

In determining the presence of glucose in urine, it should be remembered that "true glucose" must exceed 10 mmol/L (180 mg/ dl) before glucose can pass into the urine (Renal threshold).

The renal threshold is, however, elevated in diabetic kidney. 

• Also, the renal threshold increases with age. In some elderly patients no.glycosuria may be present even with serum glucose level as high as 11.1 mmol/L (200 mg/dl).

Methods of screening for urine glucose are discussed later in the URINE ANALYSIS. 

2. Fasting blood sugar 

It is preferable to use plasma for this test. Glucose levels in excess of 6.6 mmol/L (120 mg/dl) is suggestive of diabetes mellitus; and values between 6.0 to 6.6 mmol (110 to 120 mg/dl) are doubtful and should be confirmed by performing the glucose tolerance test. 

• It is important to remember that conditions such as emotional hyperglycaemia resulting from secretion of epinephrine: general brain damage such as skull

3. Two-hour post-prandial (pp) blood glucose

Two hours after the patient has broken fast by being fed on adequate carbohydrate meal, a single blood sample is collected and analysed.

• Glucose level in excess of 10 mmol/L (180 mg/dl) is highly suggestive of diabetes mellitus and should be confirmed with a GTT. 

A single two-hour pp glucose level has the limitations due to

(i) Delayed peak level due to slow absorption

(ii) Early hyperglycaemia due to rapid absorption

(iii) Quick fall in concentration of blood glucose level due to the release of insulin.

(iv) Wrong specimen collection timing.

4. Glucose Tolerance Test (GTT) 

This is also usually referred to as oral glucose tolerance test (OGTT). Glucose tolerance test (GTT) measures the ability of the body to tolerate a measured dose of glucose. 

• The rate of glucose absorption and response of insulin mainly determines the extent of glucose tolerance as shown by the changes in the level of blood glucose.

Screening Tests for Diabetes Mellitus

Method 2 

One can prepare a curve of blood glucose level against minutes (time) for the GTT. Compare it with a normal curve (Fig. 3.3).

 

Method 3

Wilkerson point system

Wilkerson point system
Time	mmol/L of glucose	Point
Fasting	7.0 or more	1.00
1 hour	10.0 or more	0.5
2 hour.	8.0 or more	0.5
3 hour	7.0 or more	1.00

The GTT is diagnostic of diabetes mellitus with this point system, if

• Two or more points are scored with up to 3 hour sample.
• One or more points are scored with up to 2 hour sample.