THE USE OF SMALL ENDOSCOPIC BIOPSIES IN THE MEASUREMENT OF DISACCHARIDASE ACTIVITIES AND THE EFFECT OF DUODENAL ULCERATION

Objectives: To define a reference range for disaccharidase (sucrase, m altase, lactase) activities for duodenal biopsy specimens taken by sma ll (3.7 mm and 2.5 mm open bite) forceps; to determine inter-patient, inter-biopsy and intra-assay variation, and to investigate whether duo denal ulcers affect disaccharidase activities. Design: The reference r ange was derived retrospectively from biopsy specimens from 1 86 patie nts undergoing duodenal biopsy for gastrointestinal symptoms (52 with abnormal histology were excluded). Prospective studies compared 2.5 wi th 3.7 mm forceps data and measured inter-patient, inter-biopsy and in tra-assay variation. Method: The reference range was defined by analys is of probit plots; 2.5 mm forceps specimens were compared with those taken with 3.7 mm forceps in 20 patients biopsied with both forceps. E ight patients with duodenal ulceration had disaccharidase activities m easured before and after a course of treatment. Results: The reference range for lactase was 3-58 U/g protein, for maltase 58-531 U/g protei n and for sucrase 10-114.5 U/g protein. Three clusters of lactase acti vity were seen: a normal group, a profoundly hypolactasic group and an intermediate group. Biopsy specimens taken by 2.5 and 3.7 mm forceps produced similar results. The intra-assay and inter-biopsy variation o bserved was acceptable for disaccharidase activities. Duodenal ulcerat ion does not affect disaccharidase activities obtained from the second part of the duodenum. Conclusions: Endoscopic biopsies, performed wit h 2.5 and 3.7 mm forceps, from the second part of the duodenum are val id for disaccharidase activity assays. An appropriate reference range should be used. Subjects with lactase activity less than 3 U/g protein represent patients with phenotypic variation and may have a mosiac pa ttern of lactase expression. Duodenal ulcers do not affect disaccharid ase activity results.