The diagnosis of lactose malabsorption.

Abstract

Jejunal lactase activity was compared to the results of oral lactose tolerance tests and glucose-galactose tolerance tests in controls and in a number of patients with various gastrointestinal diseases including 34 patients with primary or secondary lactose malabsorption.The reproducibility of the maximum blood sugar rise following lactose or glucose-galactose was good in 20 and 16 patients respectively.A high correlation between maximum blood sugar rise during an oral lactose tolerance test and the ratio between the blood sugar rises following oral ingestion of lactose and of glucose-galactose was present in 41 patients.The relation between jejunal lactase activity and the results of oral lactose or glucose-galactose tests was fairly good.It is concluded that an oral lactose tolerance test is usually sufficient to make a diagnosis of lactose malabsorption. A control test with glucose-galactose should always be performed if the lactose test indicates lactose malabsorption.Jejunal lactase activity should be determined whenever possible. A low jejunal lactase activity must be present in lactose malabsorption. However, it is not per se diagnostic, since normal lactase activity may be present at a more distal level of the small intestine. This may result in normal lactose absorption.