Cholinesterase determinations

Laboratory tests are of value but must be interpreted with care because of possible false results. Our experience notes that these tests are only helpful when certain precautions are taken into consideration, and the results correctly interpreted. For example, taking blood specimens too early or too late, or not containing them in proper temperatures (as in the case of erythrocyte cholinesterase determination), can give very misleading results. The tim-... 

W. Kalow, K. Genest, A Method for the Detection of Atypical Forms of Serum Cholinesterase. Determination of Dibucaine Numbers , Can. J. Biochem., 35, 339-346 (1957). 

Not only is the methodology non-specific, but the determination itself can be questionable because of the instability of the enzyme-carbamate complex. As with cholinesterase determinations for organophosphates, the method can be highly variable even within the same laboratory. 

Alkyl phosphorus compounds can be detected in serum by performing the cholinesterase determination on (a) a sample of normal serum, (b) the test serum, and (c) 10 p, of normal serum + 20 ul of test serum. If a low value is obtained from (b), this could be due to a low cholinesterase from liver disease or other causes. A value for (c) which is lower than the sum of the results from (a) and (b) indicates the presence of an inhibitor. Usually, in organophosphorus poisoning, the result from (c) is lower than that from (a). 

A very sensitive and commonly used method for cholinesterase determination was described by Ellman et al. (1961), based on hydrolysis of the thiochohne substrates acetyl- and butyrylthiocholine or others. After enzymatic hydrolysis, the relevant acid and thiochohne are released... 

In a practical way, the best appreciation of cholinesterase was performed using individual norms for RBC AChE. It seems to be the most sensitive parameter for monitoring cholinesterase changes in exposed workers, followed by a sensitivity for whole blood hemolysate. Plasma BuChE activity is not so specific and is a sensitive parameter. A decrease of 30% of individual norms seems to be critical for further consideration. In conclusion, cholinesterase determination in blood (especially RBC AChE) is a good parameter for monitoring and laboratory examination of... 

Plasma cholinesterase determinations have been helpful in assessing the suitability of a patient for shunt operations in portal hypertension or for liver transplantation (E18). Obstructive jaundice is not accompanied by a reduction of cholinesterase activity unless there is also damage to the hepatocytes. In cases of fatty liver, the plasma cholinesterase activity is generally normal or high. As indicated above, there is a positive correlation between the enzyme activity and plasma lipids or lipoproteins (CIO, C16, K36). 

According to the procedure and laboratory instrumentation, the most common methods of cholinesterase determination are as follows ... 

Cholinesterase activity is fundamentally important for the diagnosis of intoxication with cholinesterase inhibitors, including OP and carbamates (B2, C8, Ml, M2). On the other hand, the activity depends on many other factors and, therefore, cholinesterase determination is of diagnostic importance in different pathological states, not only intoxications (B2, Bll, B35, R2). The activity of these enzymes (AChE and BuChE) is influenced by sex, age, nutrition, hormonal factors, irradiation, etc. (B38, D4, H7, H8, S21, S24, W4). The variation of BuChE activity is greater than that of AChE (B2, B38, K46) and it is genetically determined (B38, W4). 

Kalow W, Genest K. A method for the detection of atypical forms of human serum cholinesterase Determination of dibucaine numbers. Can J Biochem Physiol. 1957 35 339-346. 

---