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, maltase, lactase) activities for duodenal biopsy specimens taken by small (3.7 mm and 2.5 mm open bite) forceps; to determine inter-patient, inter-biopsy and intra-assay variation, and to investigate whether duodenal ulcers affect disaccharidase activities. Design: The reference range was derived retrospectively from biopsy specimens from 1 86 patients undergoing duodenal biopsy for gastrointestinal symptoms (52 with abnormal histology were excluded). Prospective studies compared 2.5 with 3.7 mm forceps data and measured inter-patient, inter-biopsy and intra-assay variation. Method: The reference range was defined by analysis 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. Eight patients with duodenal ulceration had disaccharidase activities measured 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 protein and for sucrase 10-114.5 U/g protein. Three clusters of lactase activity 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 observed was acceptable for disaccharidase activities. Duodenal ulceration does not affect disaccharidase activities obtained from the second part of the duodenum. Conclusions: Endoscopic biopsies, performed with 2.5 and 3.7 mm forceps, from the second part of the duodenum are valid 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 pattern of lactase expression. Duodenal ulcers do not affect disaccharidase activity results.