glucose tolerance test indication and procedure

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1. 1   Prakash Mishra GLUCOSE TOLERANCE TEST

2. 6/6/2017 2 Glucose tolerance means ability to the body to utilize glucose in blood circulation. Glucose tolerance test : The measurement of plasma glucose before and after a specific amount of glucose given orally should provide a standard method to evaluate individuals and specific values for normal and disease. GLUCOSE TOLERANCE TEST

3. 3 This test is used to assist in the diagnosis of diabetes mellitus (DM). It is also used in the evaluation of patients with hypoglycemia. 2017/6/6 USES

4. 6/6/2017 The GT test may be used for the following condition: Patients with a family history of diabetes. Patients who are massively obese. Patients with a history of recurrent infections. Patients with delayed healing of wounds (especially on the lower legs or feet). Women who have a history of stillbirths, premature births, or large babies. Patients who have transient glycosuria or hyperglycemia during pregnancy or following myocardial infarction (MI), surgery, or stress. INDICATION OF GLUCOSE TOLERANCE TEST 4

5. 6/6/2017 5 a) In proven cases of diabetes mellitus the test is not required. b) GTT is required only in doubtful cases, it is not recommended for follow up of patient. c) Patients with serious concurrent infections or endocrine disorders, because glucose intolerance will be observed even though these patients may not be diabetic. CONTRAINDICATIONS

6. 6 Dizziness, tremors, vomiting, sweating, or fainting may occur during testing. If these symptoms occur, a blood specimen is obtained, and measure the blood glucose. If the glucose level is too high, the test may need to be stopped and insulin administered. POTENTIAL COMPLICATIONS 2017/6/6 6

7. 7 Smoking. Stress Exercise during the test can affect glucose levels. Fasting or reduced caloric intake before the GT test can cause glucose intolerance. Drugs INTERFERING FACTORS 7

8. 8 Standard Oral glucose tolerance test I/V Glucose tolerance test Mini Glucose tolerance test TYPE OF GLUCOSE TOLERANCE TEST 2017/6/6 8

9. 9 Explain the procedure to the patient. Educate the patient about the importance of having adequate food intake with adequate carbohydrates (150 g) for at least 3 days before the test. Instruct the patient to fast for 12 hours before the test. Instruct the patient to discontinue drugs (including tobacco) that could interfere with test results. Give the patient written instructions explaining the pretest dietary requirements. Obtain the patient's weight to determine the appropriate glucose loading dose (especially in children). patient preparation 2017/6/6 9

10. 10 At about 8 a.m. the fasting blood and urine samples are collected. These are called zero samples. Administer the prescribed oral glucose solution , usually 75 g of glucose for non-pregnant patients or 100 g for pregnant patients. The glucose dissolve in 300 ml of lemon juice/water mixture within 5min after taking sample . PROCEDURE OF OGTT 2017/6/6

11. 11 In pediatric patients 1.75 g of glucose / kg body weight is given. Instruct the patient to ingest the entire glucose load. Tell the patient that he or she cannot eat anything until the test is completed. However, encourage the patient to drink water. No other liquids should be taken during the testing period. 2017/6/6 11

12. 12 Inform the patient that tobacco, and smoking are not allowed. Collect a venous blood &urine sample at 30 min. interval for upto 150 min. Glucose is estimated in all the blood samples. Urine is analyzed for the presence of glucose. 2017/6/6 12

13. 2017/6/6 13 LABORATORY PROFILE OF A NORMAL PERSON AFTER GLUCOSE LOAD Fasting 30 min. 60 min. 90 min. 120 min. 150 min. Blood Glucose (mg/dl) 75 130 150 110 90 70 Urinary Glucose nil nil nil nil nil nil

14. 2017/6/6 14 Normal GLUCOSE TOLERANCE CURVE Fasting blood glucose (zero hour sample) is 75 mg /dl . Which is well within the normal r ange (normal 60-100 mg/dl). There is rise of blood glucose after glucose load and the peak value is observed at I hour.

15. 15 Normally there is a rapid insulin response to the ingestion of a large oral glucose load. This response peaks in 30 to 60 minutes and returns to normal in about 3 hours. Patients with an appropriate insulin response are able to tolerate the dose quite easily, with only a minimal and transient rise in plasma glucose levels within 1 to 2 hours after ingestion. Glucose will not spill over into the urine in normal patients. NORMAL GLUCOSE TOLERANCE 2017/6/6 15

16. 2017/6/6 16 16 LABORATORY PROFILE OF A DIABETC PATIENT AFTER GLUCOSE LOAD Fasting 30 min. 60 min. 90 min. 120 min. 150 min. Blood Glucose (mg/dl) 130 200 280 260 220 170 Urinary Glucose nil ++ ++ ++ ++ nil Fasting 30 min. 60 min. 90 min. 120 min. 150 min. Blood Glucose (mg/dl) 230 300 345 365 350 330 Urinary Glucose ++ +++ +++ +++ +++ +++ Moderate Diabetic Curve Severe Diabetic Curve

17. 17 DIABETIC CURVE 2017/6/6 17

18. Fasting 30 min 60 min 90 min 120 min 150 min 180 min Blood Glucose (mg/dl) 90 130 150 140 120 100 90 Urinary Glucose nil + + + + ± nil 2017/6/6 18 18 LABORATRORY PROFILE OF A PATIENT HAVING RENAL GLYCOSURIA

19. 19 Blood glucose levels are within the normal limits but urine glucose is positive. Glucose tolerance curve is normal. Thus glucose is found in some of the samples depending upon the renal threshold . There is lowering of renal threshold due to renal tubular defect in glucose absorption. GTT is also useful in the diagnosis of this inherited renal tubular defect. RENAL GLYCOSURIA 2017/6/6 19

20. 20 Early diabetes mellitus, Pregnancy, Renal disease, Heavy metal poisoning Deficiency of carrier protein (SGLT-2). Renal glycosuria can also be observed in children of diabetic parents. CAUSE OF RENAL GLYCOSURIA 2017/6/6 20

21. Fasting 30 min 60 min 90 min 120 min 150 min 180 min Blood Glucose (mg/dl) 90 230 180 150 120 100 90 Urinary Glucose nil + + nil nil nil nil 2017/6/6 21 21 LABORATRORY PROFILE OF A PATIENT HAVING LAG CURVE

22. 22 Fasting blood glucose is normal. Sharp rise within 30 minutes to one hour The blood glucose levels exceed the renal threshold. The decline is rapid and the normal levels are attained back. Some of the urine samples contain glucose, where the blood glucose is above the renal threshold. This is due to an increased rate of glucose absorption from the gut (sometimes in hyperthyroid). The increase in blood glucose is due to delay in insulin action. (Insulin function lagging behind, hence called Lag Curve) LAG CURVE 2017/6/6 22

23. 23 Hyperthyroidism Pregnancy After gastro-enterostomy Early diabetes mellitus CAUSE OF LAG CURVE 2017/6/6 23

24. 24 Fasting blood is ≤80 mg/dl. All samples show low blood glucose. Urine glucose is negative. Flat curves are seen in patients with hypoactivity of other endocrine organs, e.g. in hypopituitarism and Addison’s disease, malabsorption . FLAT CURVE 2017/6/6 24

25. This test is undertaken for patients with malabsorption . Under these conditions oral glucose load is not well absorbed and the results of oral glucose tolerance test become inconclusive. The values for the IV GT test differ slightly from those of the oral GT test because IV glucose is absorbed faster. IV GLUCOSE TOLERANCE TEST 2017/6/6 25

26. I/V glucose tolerance test is carried out by giving 25 g of glucose dissolved in 100 ml intravenous injection within 5 minutes. Completion of infusion is taken as 0 time. Blood samples are taken at 10 minutes interval for the next hour. The peak value is reached within a few minutes and the value touches to near normal in 45-60 minutes. PROCEDURE 2017/6/6 26

27. 27 In normal individuals, blood glucose level returns to normal within 60 minutes . In diabetes mellitus, decline is slow . The initial values are attained in 120 minutes. INTERPRETATION 2017/6/6 27

28. As per current WHO recommendations, in the mini or modern glucose tolerance test, only two samples are collected , Fasting (zero hour) and 2 hour post glucose load. Urine samples are also collected during the same time . The diagnosis is made from the variations observed in these results. MINI GTT 2017/6/6 28

29. 29 Decrease Glucose Tolerance Diabetes mellitus (DM): This disease is defined by glucose intolerance and hyperglycemia. Acute stress response Cushing syndrome Chronic renal failure Glucagonoma Acute pancreatitis Diuretic therapy Corticosteroid Myxedema After gastrectomy . CLINICAL SIGNIFICANCE 2017/6/6 29

30. Increased Glucose Tolerance Increased carbohydrate tolerance is observed in all c o nditions that cause hypoglycemia :- Hypopituitarism Hyperinsulinism Hypothyroidism Adrenal Cortical Hypofunction GLUCOSE TOLERANCE 2017/6/6 30

31. 6/6/2017 31 Thank you