Glucose Tolerance Test

Powerpoint Presentation is prepared by Dr. Raihan Mannan, JN Medical College, AMU, ALIGARH

1. GLUCOSE TOLERANCE TEST By dr raihan mannan JR-1, Deptt . of physiology JNMCH, amu , aligarh

2. CONTENTS DEFINITION INDICATION FOR OGTT CONTRAINDICATION FOR OGTT PREPARATION OF THE PATIENT CONDUCTING THE GLUCOSE TOLERANCE TEST NORMAL VALUES AND INTERPRETATION DIAGNOSTIC CRITERIA FOR DM GESTATIONAL DM

3. DEFINITION Glucose tolerance means ability of body to utilise glucose GTT is well standardised test, and is highly useful to diagnose diabetes mellitus in doubtful cases Commonly referred to as oral glucose tolerance test (OGTT)

4. INDICATION FOR OGTT Patient has symptoms suggestive of diabetics mellitus Fasting blood sugar value is inconclusive (between 110 and 126 mg/dl) During pregnancy, excessive weight gaining is noticed, with a past history of big baby (more than 4 kg) or past history of miscarriage To rule out benign renal glycosuria

5. CONTRAINDICATION FOR OGTT There is no indication for doing OGTT in a person with confirmed diabetics mellitus GTT has no role in follow-up of diabetics It is indicated only for the initial diagnosis The test should not be done in ill patients

6. PREPARATION OF THE PATIENT The patient is instructed to have good carbohydrate diet for 3 days before to the test Diet containing about 30-50 gm of carbohydrate should be taken on the evening before to the test (otherwise carbohydrate may not be tolerated even in a normal person) Patient should avoid drugs likely to influence the blood glucose levels Patient should not do smoking during the test High effort exercise on the previous day is to be avoided Patient should not take food 8 PM the previous night Should not take any breakfast, this is to ensure 12 hours fasting

7. PREPARATION OF THE PATIENT (cont…)

8. hours 1 2 3 50 100 150 200 250 300 350 Renal threshold Normal person Black Alimentary glycouria Yellow Renal Glycosuria Purple Diabetes mellitus Orange Plasma glucose (mg/dl)

9. CONDUCTING THE GLUCOSE TOLERANCE TEST AT ABOUT 8 am, a sample of blood is collected in the fasting state, urine sample is also obtained Glucose load dose: the dose is 75 g anhydrous glucose (82.5 g of glucose monohydrate) in 250-300 ml of water When the test is done in children, the glucose dose is adjusted as 1.75 g/kg body weight Sample collection WHO recommendation is to collect only for the fasting and two hours post glucose load samples of blood and urine, this is called as mini-GTT The dose should be drunk within 5 minutes

10. NORMAL VALUES AND INTERPRETATION In a normal person, fasting plasma glucose is 70-110 mg/dl The glucose level rises and reaches a peak within hour and come down to normal fasting level by 2-2:30 hrs, this is due to secretion of Insulin in response to the elevation in blood glucose None of the glucose sample shows the any evidence of glucose

11. DIAGNOSTIC CRITERIA FOR DM If the fasting plasma sugar is more than 126 mg/dl on more than one occasion If two hour post glucose load value of OGTT is more than 200 mg/dl If both fasting and 2 hrs values are above this level If the random plasma level is more than 200 mg/dl on more than one occasion

12. Results: Fasting plasma glucose should be below 110 mg/ dL Fasting levels between 110 and 125 mg/ dL are borderline " impaired fasting glycaemia " Fasting levels repeatedly at or above 126 mg/ dL are diagnostic of diabetes. A 1 hour GTT (Glucose Tolerance Test) glucose level below 180 mg/ dL is considered normal For a 2 hour GTT (Glucose Tolerance Test) with 75g intake glucose level below 140 mg/ dL is normal Blood glucose between 140 mg/ dL and 200 mg/ dL indicate " impaired glucose tolerance ” Blood glucose levels above 200 mg/ dL at 2 hours confirm a diagnosis of diabetes

13. ACOG recommends a two-step procedure: First step is a 50g glucose dose over one hour If blood glucose level is more than 140 mg/ dL , it is followed by a 100 gram glucose dose over 3 hours The diagnosis of gestational diabetes is then defined by a blood glucose level exceeding the cutoff value on at least two intervals , with cutoffs as follows: Before glucose intake (fasting): 95 mg/ dL 1 hour after drinking the glucose solution: 180 mg/ dL 2 hours: 155 mg/ dL 3 hours: 140 mg/ dL GESTATIONAL DM

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