Acetylcholinesterase activity in rectal biopsies: an assessment of its diagnostic value in Hirschsprung's disease.

Acetylcholinesterase (AChE) activity was measured in rectal suction biopsies from 392 patients investigated for Hirschsprung's disease (HD). Results in HD (2.7-23.7 RU; n = 37) were not clearly differentiated from those in patients without HD (0.6-18.0 RU; n = 355). Sample instability was shown not to be a significant cause of error. From analysis of duplicate biopsies and a consideration of false-negative results, tissue inhomogeneity or incorrect siting of the biopsy appeared likely causes of error. Examination of a number of possible diagnostic decision levels indicated an optimal choice of AChE activity greater than 10 RU with an AChE activity not less than 60% of total cholinesterase activity. At a prevalence of 10%, this decision level resulted in sensitivity of 64.9%, specificity 98.7%, predictive value of positive 85.7%, and predictive value of negative 96.3%. The false positives (n = 4) and false negatives (n = 13) by these criteria were examined to detect possible common features.