Cholinesterase In Serum/plasma
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Contents |
Indications
-
- sensitivity to succinylcholine administration
Reference-interval
Principle
- The kodak Ektachem Clinical Chemistry Slide (CHE) quantitatively measures Cholinesterase activity in serum or plasma. Cholinesterase is a Multiple-Point Rate Test.
- The Kodak Ektachem Clinical Chemistry Slide (CHE) is a dry, multilayered element coated on a clear polyester support. An 11 uL drop of sample is deposited on the slide & is evenly distributed by the spreading layer. Cholinesterase hydrolyze butyrylthiocholine to thiocholine. The liberated thiocholine reduces potassium hexacyanoferrate III ( potassium ferricyanide) to potassium hexacyanoferrate II. The rate of color loss is monitored by reflectance spectrophotometry & is proportional to the amount of cholinesterase activity present in the sample. The assay wavelength is 400 nm. Assay time is approximately 5 minutes, & the assay temperature is 37 degrees C.
Clinical-significance
- there are two types of Cholinesterase:
- acetylcholinesterase ( EC 3.1.1.7),
- found in red blood cells & nerve tissues, lung, spleen
- hydolyzes acetylcholine in synaptic clefts & at the motor endplate
- pseudocholinesterase ( EC 3.1.1.8),
- found in plasma, liver, heart & other tissues (butrylcholinesterase)
- its physiologic role is unknown, but it is important in cleavage of succinylcholine & mivacurium, paralyzing agents used during surgery
- at high concentrations, acetylcholine (0.01 M) inhibits acetylcholinesterase but not pseudocholinesterase
- acetylcholinesterase, but not pseucholinesterase hydrolyzes acetyl-beta-methylcholine
- pseucholinesterase, but not acetylcholinesterase hydrolyzes butyrylcholine & benzoylcholine
Increases
- clinical disorders:
Decreases
- pesticide poisoning
- organophosphate & carbonate pesticides are inhibitors of both cholinesterase & acetylcholinesterase
- although the toxic effect is caused by inhibitors of acetylcholinesterase in nerve endings, cholinesterase is often used clinically because it is present in serum in high activities & is easy to measure
- clinical disorders
-
- cirrhosis, hepatitis, carcinoma with metastasis to the liver, hepatic congestion of heart failure, & hepatic amebiasis lower cholinesterase activity
- a decrease in CHE activity is considered a sensitive measure of a drop in liver synthetic capacity, since high levels of cholinesterase are normally present in serum
- genetic cholinesterase variants
- sensitivity to succinylcholine administration
- succinylcholine is a short-acting muscle relaxant administered during surgery
- it is a reversible inhibitor of acetylcholinesterase
- individuals without sufficient serum CHE activity or with certain genetic variants may be unable to metabolize the drug quickly, resulting in prolonged apnea
- pharmaceutical agents
- in vivo effects
- anabolic steroids, carbamates, cimetidine, cyclophosphamide, echothiophate iodide, estrogens, glucocorticoids, lithium, neostigmine, neuromuscular relaxants ( pancuronium, succinylcholine), oral contraceptives, organophosphorous insecticides, phenelzine, phenothiazines, physostigmine, radiographic agents ( iopanoic acid) ranitidine, streptokinase, testosterone
- chemical interferences
- borate, citrate, detergents, fluoride, heavy metals, pyrophosphate, serum separators, tertiary & quaternary amines
Specimen
- The recommended specimen is 11 uL of serum or plasma. Collect specimens by standard venipuncture technique. Heparin may be used as an anticoagulant. No special preparation is necessary.
- SPECIAL PRECAUTIONS:
- Minimum sample size is 0.5 milliliter, with an optimum size of 1.0 mL or larger.
- Samples that have CHE activity that exceeds the analyzers dynamic range should be diluted with Kodak Ektachem Solution (7% BSA)/ Bovine Serum Albumin & reanalyzed. Multiply results by the dilution factor to obtain the original samples CHE activity. The Kodak Ektachem 700 Analyzer's dynamic range for CHE is 0.20-12.50 U/ mL.
Interferences
- Preliminary data indicated that hemolysis, icterus and lipemia do not interfere with this method.
- Extremely high levels (40mg/dL) of Ibuprofen can cause aa 19% negative bias. Therapeutic levels up to 20mg/dL do not interfere.
- Low pH (6.8) causes a 15% negative bias.
- Procainamide is a known CHE inhibitor. A negative bias of 2% per mg/dL of procainamide is observed.
- L-DOPA at a level of 300 ug/mL causes a 25% positive bias at 4.5 U/mL of cholinesterase.
- Phenazopyridine at a level of 80 ug/dL causes a 34% negative bias at 4.5 U/mL of cholinesterase.
More General Terms
Additional Terms
- dibucaine number
- pseudocholinesterase (cholinesterase-2, acylcholine acylhydrolase, butyrylcholinesterase, BuChE, BCHE)
References
- Kodak Ektachem 700 Analyzer Operator's Manual, Kodak Clinical Products, Rochester, New York.
- Kodak Ektachem Slide Package Inserts, Kodak Clinical Products Rochester, New York.
- Kodak Ektachem Training Manual, Kodak Clinical Products, Rochester, New York.
- Clinical Guide to Laboratory Tests, 3rd ed. Teitz ed., W.B. Saunders, 1995
- Henry's Clinical Diagnosis & Management by Laboratory Methods, 21st edition, McPherson RA & Pincus MR (es), W.B. Saunders Co., Philadelphia, PA. 2007, pg 257
- Serum dibucaine number [1]
- Alexander DR Pseudocholinesterase Deficiency [2]
