[Clinical significance of serum cholinesterase concentrations determined by enzyme-linked immunosorbent assay (ELISA)].

We developed a sensitive enzyme-linked immunosorbent assay (ELISA) for measurement of the protein mass of serum cholinesterase (CHE). In our ELISA system, a combination of a monoclonal antibody (a capture antibody) and an anti-CHE rabbit antibody (a second antibody) against CHE were used for the specific determination of CHE. The formed antigen-antibody complexes were detected with an alkaline phosphatase-labeled anti-rabbit IgG antibody. Using this ELISA system, we investigated for a possible relationship between the protein mass value and the catalytic activity of serum CHE in three patients groups with different clinical findings: control subjects selected randomly from outpatients (Group A), individuals with a low serum CHE activity including genetic variants (Group B) and patients with sarin poisoning (Group C). The CHE mass value correlated closely with the CHE activity in Group A, as previously reported. In Group B, a less significant correlation than in Group A was observed because both the CHE mass value and the CHE activity were disturbed at relatively lower levels. However, no discrepant cases were observed. On the other hand, in Group C, patients with serious sarin poisoning showed significant discrepancies between the mass value and activity of CHE before medical treatments, indicating that the inhalation of sarin did not affect the protein mass level but did affect the activity of serum CHE. As the patients recovered during the treatments, their CHE activities increased to the levels expected from the regression curve obtained with Group A, whereas the mass values were almost unchanged. In conclusion, protein mass determination of serum CHE provides valuable information concerning the target value of the serum CHE activity for the treatment of patients with organophosphate insecticide poisoning as well as for investigating the specific activity of genetic variants of serum CHE.