Amylase, gamma-glutamyl transferase and cholinesterase - general information, principles of analytical methods, sources of errors, indications for analysis, biological material, reference ranges, interpretation of results.
Amylase hydrolyses alpha-bonds of large alpha-linked polysaccharides such as starch and glycogen, yielding glucose and maltose. Amylase is one of several enzymes produced by the pancreas to help digest carbohydrates. Amylase is also produced by salivary glands. There are several more isoenzymes and one form of macro-amylase, which is a complex of immunoglobulins of the patient.
Analytical methods for amylase: Kinetics - with soluble substrates, mainly para-nitrophenyl-maltoheptaose.
Source of errors: NaCl residues strongly activate salivary and pancreatic amylases. Saliva falling into the serum may also fail the study. Captopril and corticosteroids interfere positively, and anabolic steroids are negative.
Indications: differential diagnosis of acute pancreatitis from other acute abdominal diseases.
Biological material: Blood is taken under standard conditions and determined in serum, taking precautions to avoid saliva or NaCl entering the material.
Reference ranges: 140 U / l, and in urine up to 400 U / l.
Interpretation of results:
- Above 10x due to acute pancreatitis
- 5-10x due to perforated duodenal ulcer, chronic recurrent pancreatitis, some pancreatic carcinomas
- Up to 5x due to chronic renal failure, morphinism, mumps
Gamma-glutamyl-transferase transfers gamma-glutamyl functional groups. GGT is an enzyme found in many organs, such as the kidney, liver, spleen and pancreas; however, the main source of GGT in the blood is the liver. It has cell membrane localization.
Analytical method: Kinetic enzymatic hydrolysis of gamma-glutamyl esters with aromatic chromogens.
Interferences: GGT levels fall after meals. Numerous drugs can raise GGT levels, including barbiturates, NSAIDs, aspirin.
Indication for analysis: useful in assessing liver function associated with alcohol induced liver disease. To differentiate between liver and bone disease as a cause for elevated alkaline phosphatase.
Reference ranges: 40 to 78 U/L.
Preparation of the patient and specimen - blood is obtained under the standard conditions and serum without haemolysis is separated.
Interpretation of results:
- Above 10x due to cholestasis, chronic alcoholism
- 5-10x due to hepatitis, cirrhosis, liver tumours
- Up to 5x due to treatment with phenobarbital, and severe alcohol intoxication
Cholinesterase two separate cholinesterase enzymes in the body: acetylcholinesterase, found in nerve endings, and the grey matter of the brain, and pseudocholinesterase found in the serum as well as the liver, muscle, pancreas, heart, and white matter of the brain. Acetylcholinesterase catalyses the hydrolysis of the neurotransmitter acetylcholine into choline and acetic acid.
Analytical methods: Kinetic - Measurement of the colour product by the hydrolysis of the acetyl / butyryl thiocol iodide substrate.