Automation of serum cholinesterase assay--paediatric and adult reference ranges

Serum cholinesterase (CHE) activity falls dramatically with organophosphate poisoning. In view of the need for an accurate, reproducible and inexpensive method for screening large numbers of farmworkers and others exposed to organophosphates, a manual commercial method was modified for use on an automated (centrifugal) chemistry analyser. The resultant procedure can be performed rapidly with a 24-fold cost-saving over the manual method. The volume of sample required is small, results of the automated and manual method showed excellent correlation and the reproducibility characteristics of the automated assay procedure was adequate for clinical use. Reference ranges were determined on children and adults. The results best fitted two reference ranges: children and adult females had a combined mean of 5,687 U/I with a lower (2,5 percentile) and upper (97,5 percentile) limit of 3,070 U/I and 8,483 U/I, respectively. The corresponding figures for adult men were 8,607 U/I (mean), 4,687 U/I and 9,116 U/I. The results also strongly suggested that pregnant women and women taking oral contraceptives had CHE activities approximately 12% lower than the female reference range quoted above. The numbers evaluated were too small, however, to construct a separate reference range for this category.