Oral glucose tolerance test: Definition, factors affecting, preparation of patient, procedure, indications and interpretation
Definition:
Glucose tolerance is ability of the body to tolerate an extra load of glucose.
OGGT diagnostic test:
It is diagnostic test for diabetes mellitus.
Preparation for OGTT
1. The patient should have been taking carbohydrate-rich diet for at least 3 days (300 gm of carbohydrate
per day).
2. Fasting should not be less than 10 hours and not more than 16 hours.
Only water is taken after dinner.
3.
Complete mental and physical rest.
4.
No smoking is permitted.
5.
The patient should not be taking drugs that affect carbohydrate
metabolism.
Procedure
1. A fasting sample of venous blood is collected in fluoride bottle or in
gel plain tube separated immediately after blood venous blood collection(fasting
sample).
2.
The bladder is emptied completely and urine is collected for qualitative
test for glucose and ketone bodies(fasting urine).
3.
The individual is given 75 gm of glucose dissolved in water about 250 ml
to drink.
4.
Collect three venous blood specimens and urine. Draw venous blood specimen every hour after the oral glucose
( first hour, second hour and third hour).
5. Then serum glucose concentration of all three venous (including fasting sample)
samples is measured and corresponding urine samples are tested qualitatively
for presence of glucose and ketone bodies.
6.
After that, a curve is plotted which is called as “ glucose tolerance
curve” .
Indications of GTT:
- It is
performed in patients with transient glycosuria who have no clinical
symptoms of diabetes with normal fasting and post-prandial blood glucose.
- In patients
with symptoms of diabetes but with no glycosuria and normal fasting blood
glucose level.
- In patients
with or without symptoms of diabetes mellitus showing abnormal fasting
glucose, post-prandial blood glucose, or random blood glucose.
Interpretation of OGTT
a) A normal glucose tolerance
curve
·
Fasting blood glucose within normal limits(70-100mg%)
·
The highest value does not more than 160-180mg%) and returns to normal
within one hour.
·
The serum glucose level after 2½ hour is equal or near fasting glucose
level.
·
No glucosuria at all specimens.
b) Diabetic type of glucose
tolerance curve
·
Fasting blood sugar is more than 110 mg%.
·
The highest value exceeds 180 mg%
·
The blood glucose doesn't return to the fasting level within 2½ hour.
·
glucosuria at all specimens.
c) Renal glycosuria curve
·
Glucose appears in urine at levels of blood glucose much below 170 mg%
·
This is due to idiopathic, certain renal diseases or pregnancy
d) Lag curve
· Fasting blood glucose is normal but raises rapidly in the ½hour to 1 hour and exceeds 180 mg% and show
glucosuria.
· Then the glucose returns to normal rapidly and complete.
· This occurs in pregnancy, hyperthyroidism and early diabetes
For more information press https://dbwangamal.blogspot.com
تعليقات
إرسال تعليق