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.

Key-words:

• Intestine, small
• malabsorption syndromes
• disaccharides
• lactose
• biopsy
• enzyme tests