Estimation of plasma glucose with frequently asked viva questions

1. ESTIMATION OF
BLOOD GLUCOSE
MLT biochemistry studies

2. Indications :
◦ Increased blood glucose level :
- increased thirst
- more frequent urination
- blurred vision
- fatigue
- wounds that are slow to heal

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◦ Low blood glucose level :
- anxiety
- sweating
- trembling
- hunger
- confusion

4. Importance of glucose estimation :
◦ To establish the diagnosis of diabetes mellitus
◦ To monitor therapy in diabetes mellitus
◦ To evaluate disorders of carbohydrate metabolism
◦ To evaluate presence of insulinoma
◦ To evaluate clinical conditions like acidosis , ketoacidosis , dehydration , hypoglycemia
,neuroglycopenia
◦ To investigate polyuria ,polydipsia ,polyphagia , weight loss

5. Methods for glucose estimation :
1. Reduction method :
a.Folin Wu method
b.Nelson somogyi method
2. Condensation method :
a.Orthotoluidine method
3. Enzymetic method :
a. GOD – POD method
b. Hexokinase method

6. Principal by GOD – POD method
Glucose reacts with glucose oxidase to form gluconic acid and hydrogen peroxide .
Peroxidase acts on hydrogen peroxide to form nacent oxygen and water molecule.
Nacent oxygen reacts with 4 – amino antipyrine to form pink coloured complex
quinonimine dye . The intensity of pink colour formed is directly proportional to
concentration of glucose present in given sample.The absorbence or O.D. is measured
colorimetrically at 456 nm and compared with standard treated similarly.
sample: plasma
Bulb : fluoride bulb

7. Reagents :
1. Glucose reagent :
. Glucose oxidase
. Peroxidase
. 4 – amino antipyrine
2. Glucose standard solution :
Concentration : 1mg/ml

8. Procedure :

9. Calculation:

10. Normal ranges :
◦ Fasting : 70-110 mg/dl
◦ Random : less than 126 mg/dl
◦ Post –prandial : upto 126 mg /dl

11. Clinical significance :
A. Hyperglycemia :
1.Physiological causes :
- Alimentary – after high carbohydrate intake
- Emotional – stress , anger, anxiety
- pregnancy
2. Pathological causes :
- diabetes mellitus
- hyperthyroidism
- hyperadrenalism
- hyperpituitarism

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- diseases of pancreas like pancreatitis and carcinoma
- cerebrovascular accidents
- iatrogenic
- idiopathic
B.Hypoglycemia :
1. Physiological causes :
- during starvation
- after severe excercise

13. 2. Pathological causes:
a. Due to excess insulin eg;
- excessive dose of insulin
- no food intake after insulin administration
- tumors of pancreas
b. Glycogen storage disorders
c. Hypoactivity of thyroid, adrenal and pituitary glands
d.Iatrogenic
e. Idiopathic
f. Addison’s disease

14. Viva questions :
◦ Purpose of using fluride bulb :
fluoride bulb maintains stable blood glucose level by inhibiting glycolysis
◦ Composition of fluride bulb :
- sodium fluoride
- potassium oxalate
in 1:3 ratio
◦ Functions of components of fluride bulb:
. Sodium fluoride acts on enolase enzyme of glycolysis pathway and hence maintain stable glucose
level by inhibiting glycolysis
. Potassium oxalate prevent coagulation of blood

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◦ Hormones regulating blood glucose level :
- Insulin
- Glucagon
- Epinephrine
- GH and ACTH
- Thyroxin
- Somatostatin
◦ Why GOD – POD method is preferred over Folin Wu method ?
because GOD – POD method is specific for glucose.