cholinesterase in serum/plasma

Indications

• pesticide poisoning
• liver diseases
• pseudocholinesterase deficiency
  • sensitivity to succinylcholine administration

Reference interval

• Male: 5.90 - 12.22 U/mL
• Female: 4.65 - 10.44 U/mL

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:
  • type IV hyperlipoproteinemia
  • nephrosis
  • obesity (including diabetics)
  • psychosis
  • breast cancer

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
  • liver Diseases
    • 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
  • malnutrition
  • anemias
  • acute infections
  • myocardial infarction
  • pulmonary embolism
  • plasmapheresis
  • dermatomyositis
  • muscular dystrophy
  • post surgery
  • chronic renal disease
  • late pregnancy
  • hypoalbuminemia
  • exfoliative dermatitis
• 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:

• Remove serum or plasma promptly from the clot or cells.
• Potassium oxalate/fluoride, citrate & EDTA anticoagulants should not be used.
• Refrigerate specimens at 2-8 C if analysis not performed within 4 hours; or freeze specimens at -18 C if analysis is delayed beyond 48 hours.

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

• cholinesterase in body fluid

More specific terms

• cholinesterase in serum/plasma qualitative
• cholinesterase in serum/plasma quantitative

Additional terms

• dibucaine number
• pseudocholinesterase (cholinesterase-2, acylcholine acylhydrolase, butyrylcholinesterase, BuChE, BCHE)