Amylase (2) - PDF

SERUM AMYLASE Prepared by: Mike Lenard M. Leocadio, RMT Learning Objectives: Know the tissue distribution of Amylase Enumerate the different analytical methods for determination of Amylase Describe the two isoamylases Know the clinical significance of amylase determination Introduction...

SERUM AMYLASE Prepared by: Mike Lenard M. Leocadio, RMT Learning Objectives: Know the tissue distribution of Amylase Enumerate the different analytical methods for determination of Amylase Describe the two isoamylases Know the clinical significance of amylase determination Introduction Amylase (AMY) is an enzyme belonging to the class of hydrolases that catalyze the breakdown of starch and glycogen. Starch consists of both amylose and amylopectin. AMY is therefore an important enzyme in the physiologic digestion of starches. AMY requires calcium and chloride ions for its activation. Tissue Source The acinar cells of the pancreas and the salivary glands are the major tissue sources of serum AMY Lesser concentrations are found in skeletal muscle and the small intestine and fallopian tubes AMY is the smallest enzyme, with a molecular weight of 50,000 to 55,000. Because of its small size, it is readily filtered by the renal glomerulus and also appears in the urine Diagnostic Significance The diagnostic significance of serum and urine AMY measurements is in the diagnosis of acute pancreatitis Disorders of tissue other than the pancreas can also produce elevations in AMY levels. Therefore, an elevated AMY level is a nonspecific finding Other disorders causing an elevated serum AMY level include salivary gland lesions, such as mumps and parotitis, and other intra-abdominal diseases, such as perforated peptic ulcer, intestinal obstruction, cholecystitis, ruptured ectopic pregnancy, mesenteric infarction, and acute appendicitis. Test methodology AMY can be assayed by a variety of different methods: CARAWAY MODIFIED METHOD CALCULATION OF RESULTS Source of Error salivary AMY is preferentially inhibited by wheat germ lectin AMY in serum and urine is stable. Little loss of activity occurs at room temperature for 1 week or at 4°C for 2 months Because plasma triglycerides suppress or inhibit serum AMY activity, AMY values may be normal in acute pancreatitis with hyperlipemia REFERENCE RANGE AMY: serum, 28–100 (37°C) U/L; urine, 1–15 U/h There is no uniform expression of AMY activity, although Somogyi units are frequently used. The approximate conversion factor between Somogyi units and international units is 1.85. REFERENCE Clinical Chemistry: Principles, techniques, and Correlations, 8th ed. Michael L. Bishop, Edward P. Fody, and Larry Schoeff.