Evaluation of the UV-340 spectrophotometric determination for pseudocholinesterase activity (EC 3.1.1.8) in human serum.

A pseudocholinesterase catalytic activity assay using p-hydroxybenzoylcholine as substrate and measuring the decrease of NADPH at 340 nm was compared with a colorimetric method using acetylthiocholine as substrate. The assay is simple, uses 50 microliters serum and is performed at 37 degrees C. Precision of the UV-340 method was good except at low ranges. The catalytic activity was depressed by the anticoagulants citrate and fluoride but not by EDTA or heparin. The reference values obtained with the evaluated UV-340 method are somewhat higher than those with the colorimetric method. As the results with both methods are comparable, the choice of procedure will depend on the local facilities.