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Blood Glucose Test Dept.of Biochemistry. Determination of glucose concentration is important in the diagnosis and treatment of disorders of carbohydrate.

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Presentation on theme: "Blood Glucose Test Dept.of Biochemistry. Determination of glucose concentration is important in the diagnosis and treatment of disorders of carbohydrate."— Presentation transcript:

1 Blood Glucose Test Dept.of Biochemistry

2 Determination of glucose concentration is important in the diagnosis and treatment of disorders of carbohydrate metabolism. Values higher or lower than the reference are of diagnostic significance.

3 The source and fate of blood sugar It is tightly regulated as a part of metabolic homeostasis. Glucose levels rise after meals for an hour or two.

4 Maintaining Glucose Homeostasis Hormones play important roles in maintaining glucose homeostasis: –Insulin : decreasing( ↓ ) blood sugar levels –Glucagon, Adrenaline, Thyroxine, Glucocorticoid : increasing( ↑ ) blood sugar levels

5 Clinical significance Hyperglycaemia: blood glucose level goes above 7.0mmol/L. –The levels are increased in diabetes mellitus, hyperthyroidism and in the hyperactivity of the pituitary gland. Hypoglycemia: blood glucose level falls below 3.0mmol/L, this would lead to a loss of consciousness (coma). –Decreased levels are observed in cases of overproduction of insulin by the pancreas, with tumors of the pancreas, as well as with hypofunction of the organs involved in glucose synthesis and carbohydrate metabolism.

6 Diabetes Mellitus A condition in which the body either does not produce enough, or does not properly respond to insulin or both. This causes glucose to accumulate in the blood, often leading to various complications. hyperglycaemia Two main common forms: –Type 1 diabetes Other names: –“ Juvenile ” diabetes –Insulin dependent diabetes mellitus (IDDM) –Type 2 diabetes Other names: –“ Adult onset ” diabetes –Noninsulin dependent diabetes mellitus (NIDDM)

7 Standard reference test in diagnosis The fasting plasma glucose (FPG) test –(person who has not eaten in the past 10-14 hours) Random plasma glucose(RPG)Random plasma glucose(RPG) –(measuring plasma glucose without regard to the last food intake) 2-hour postload plasma glucose test(2h-PG) Oral glucose tolerance testOral glucose tolerance test (OGTT) (2 hours after ingestion of a glucose load of 75 g) Glycosylated hemoglobin (HbA1c)Glycosylated hemoglobin (HbA1c) (Both tests require a second confirmation)

8 According to the National Diabetes Data Group of the National Institutes of Health in 1979 the revised criteria for the diagnosis of diabetes: Diagnostic Criteria for DM ЖЖ 1. Fasting (overnight): Symptoms of diabetes and Venous plasma glucose concentration ≥ 7.0 mmol/L on at least two separate occasions. Ж Ж 2. Following ingestion of 75g of glucose: Venous plasma glucose concentration ≥ 11.1mmol/l at 2h and on at least one other occasion during the 2h test.

9 OGTT (oral glucose tolerance test) is the test to assess the ability of glucose tolerance. Glucose tolerance is the ability to dispose of a glucose load effectively. In a normal individual, blood glucose level returns to normal levels within 2hrs after ingestion of carbohydrate meal.

10 OGTT is indicated if a case is highly suspicious of being diabetic but is not diagnosed by random or fasting hyperglycemia. Which condition ? OGTT is unnecessary if the diagnosis is already established. Results of the OGTT that do not meet the criteria for diagnosing diabetes may be normal, equivocal or indicate impaired glucose tolerance. Attention:

11  Fasting 10~14hours;  A zero time (baseline) blood sample is drawn;  Drink glucose solution (75g glucose dissolve in 250~300ml H 2 O) within 5min;  Blood is drawn at 30min intervals for at least 2 hours.  All blood samples are subjected to glucose estimation while urine samples are qualitatively tested for glucose. 12345 0min30min60min90min120min

12 Fasting glucose ( mmol/L ) 2h-PG ( mmol/L ) Normal < 6.1 < 7.8 DM≥7.0≥11.1 Impaired fasting glucose(IFG) 6.1-6.9 < 7.8 Impaired glucose tolerance( IGT) < 7.0 7.8-11.0 mmol/L DM IGT IFG Normal

13 Principle Glucose is oxidized by glucose oxidase (GOD) forming gluconic acid and hydrogen peroxide (H 2 O 2 ). The H 2 O 2 formed is broken down by peroxidase (POD) to H 2 O and O 2. The latter oxidizes phenol, which combines with 4-aminoantipyrine(4-AP) to give a red colored complex. The intensity of the red colored complex is proportional to concentration of glucose in the specimen, which is measured at 510 nm. GOD Glucose+O 2 Gluconic acid +H 2 O 2 POD 2H 2 O 2 +Phenol+4-Aminoantipyrine Red quinone +4H 2 O Blood Glucose (GOD/POD method)

14 Specimens & Materials Specimen: serum Working reagent : –glucose oxidase(GOD); peroxidase(POD); phenol; 4-aminophenazone; pH7.0 buffer solution Standard glucose solution: 5.5mmol/L Water bath Pipettes Spectrophotometer

15 Method BST1T1 Working reagent (ml) 1.0 Serum (ml) -- 0.01 Standard (ml) - 0.01 - dH 2 O (ml) 0.01 -- Mix well , 37  C , 15 mins dH 2 O(ml) 0.5 Mix well, measure the Absorbance of T and S setting zero with B, λ=510nm.

16 Calculation C T (  mol/L)=A T /A S x C S C S =5.5mmol/L 3.89~6.11 mmol/L NORMAL VALUE

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