Improved accuracy of cholinesterase phenotyping after participation in a proficiency survey.

We report results of an investigation into the proficiency of cholinesterase (EC 3.1.1.8) phenotying, assessed in 13 laboratories between 1983 and 1986. Thirty-two specimens of serum were distributed for analysis: two, each in duplicate, from the eight genotypes that can be recognized by differential enzyme inhibitor numbers. The accuracy of genotype ascription was markedly improved over that observed in an earlier study in which 12 of these laboratories took part, although the proportion of clinically significant errors did not change. Consequently, although participation in a proficiency testing program can lead to a considerable enhancement of performance, we still recommend the use of reference centers for detailed cholinesterase studies.