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BLOOD AMYLASE TEST

Definition :-

Amylases are enzymes randomly split α-1,4 -glycocidic bonds on starch or related polysaccharides. The products of this action are a mixture of glucose , maltose and dextrins. Amylases are secreted by the salivary and pancereatic glands into GTI.

-Pancereatic amylases are playing the major role in digestion of starch rather than salivary amylases due to inhibition of the later by gastric HCL.

-They are 2 groups of isoenzymes

1-salivary isoenzymes[ S-type ]

2-pancereatic isoenzymes [P-type] .

-They are together about 17 isoenzymes and all play the same action.

-Amylase is the diagnostic test of acute pancereatitis and begin to rise in serum 2 hours after the onset , peaks at 24 hours , and return to normal 2-3 days later.

-Urine amylase begin to rise several hours after onset and return to normal 2 weeks later.

Clinical significance :-

– Increased in :- Parotitis , pancereatitis , intestinal obstruction or infarction , strangulated bowel , ectopic pregnancy , biliary tract diseases, peritonitis , macroamylasemia , renal failure and mumps.

– Decreased in :- Pancereatic insufficiency , advanced cystic fibrosis (CF) , Pancreatictomy and sever liver diseases.

– For urine sample collect 2,6,8,12,or 24 hours. Adjust pH to alkaline range and store at 2-8 ċ until the end of collection.

Prespecimen processing :-

patient should be fast at least 2 hours , and not drink alcohol 24 hours before.

Methodology :-

Kinetic / Maltohepatose .

Guiding Reference Value:-

Serum (25-125 U/L).

Urine ( 400-600 U/L).

Plueral and ascitic fluid slightly less than or identical to serum activity.

Limitation :-

– Urine amylase determination should not be done for females during menstruation.

– Macroamylasemia causes high serum & normal urine amylase.

– Normal serum amylase may occur in chronic pancreatitis.

– Pleural fluid amylase rise when serum amylase rise and in amylase-producing lung tumor , ovarian tumor, rupture of esophagus , perforation of thoracic duct , pulmonary TB; embolism or infarction and CHF.

– Some drugs cause elevation in serum amylase include ; corticosteroids , estrogens , methyldopa , diuretics , valporic acid and tetracycline.

– And some cause reduction in the values like ; glucose and fluorides.

– Amylase / creatinine clearance ratio is calculated as Amylase Clearance/creatinine clearance X 100

Normal ratio is 1 – 4 %

– It increase in :- Pancreatitis , large dose of corticosteroids and pancreatic cancer and

it decrease in :- Macroamylasemia.