[Application to an automatic system of a direct method for determining atypical variants of cholinesterase using succinyldithiocholine as substrate].

The determination of human serum cholinesterase (EC 3.1.1.8) is frequently requested to detect patients with atypical forms of the enzyme which reacts abnormally with succinylcholine (suxamethonium), employed as a neuromuscular blocking agent. Usually, for biochemical identification of succinylcholine sensitive individuals the standard reaction is run with and without the inhibitors, notably dibucaine. A new test for direct determination of succinylcholine sensitive individuals which use a substrate analogue of succinylcholine was applied to a automated instrument. The linearity, precision, recovery, interference and correlation of the method have been evaluated. We have estimated the reference intervals for a population of 364 healthy subjects subdivided for sex, three atypical homozygotes and two atypical heterozygotes. On the basis of analytical performance we can conclude that this test may offer a further parameter for preoperative screening of individuals with an abnormal response to the muscle relaxant succinylcholine, thus avoiding the determination of genotype by measurement of dibucaine number.