Clinical and analytical considerations in the utilization of cholinesterase measurements.

Many theories have been advanced but the true physiological function for serum cholinesterase has still not been identified. Evidence has been presented for the abnormal expression of cholinesterase genes in many types of human tumors. Cholinesterase measurements are still used to monitor exposure to organophosphate insecticides and their clinical application requires a good understanding of the inter and intra-individual variation, as well as some knowledge of the time sequence between exposure and measurement of the cholinesterase activity. The use of serum cholinesterase measurement in liver disease varies in different countries. A case has not been made for the cost-effectiveness of adding serum cholinesterase as part of a screening procedure for the diagnosis of liver disease. During the last 10 years much information has been obtained on the molecular biology and genetics of acetylcholinesterase and butyrylcholinesterase, distinct enzymes encoded by two different, but related genes. It has been established that BChE is included by a single gene which corresponds to the E1 locus. The complete amino acid sequence of human serum cholinesterase and the location of disulfide bonds within the sequence have been described. The molecular basis of many variants of human serum cholinesterase has been described in detail. It is not rare for multiple mutations to occur within a single butyrylcholinesterase gene or there may be combination of mutations. At least 11 silent variants of human butyrylcholinesterase have been identified. There still exists a wide variety of substrates and analytical conditions for butyrylcholinesterase measurement in a number of clinical situations. No real evidence has been provided for clinical value for their use in the diagnosis of Alzheimer disease or monitoring the use of cholinesterase inhibitors in the treatment of pre-senile dementia of Alzheimer type. However, the insights from molecular biology technology may well open up more challenges in a variety of clinical situations.