Lactose intolerance: lactose tolerance test versus genotyping.

OBJECTIVE

Adult lactose intolerance, which affects the majority of the population in the world, has been associated with a single nucleotide polymorphism, C-13910T, located upstream of the lactase gene.

MATERIAL AND

METHODS

Adult patients undergoing lactose tolerance tests with lactose challenge and plasma glucose measurements were included in the study comprising 44 Swedes and 7 non-Swedish individuals. A real-time PCR method was established for the genotyping.

RESULTS

Out of 51 patients 48 had concordant results on genotyping and lactose tolerance tests, e.g. -13910T/T and -13910C/T genotypes had high glucose elevations. All patients with the heterozygous genotype, -13910C/T, had high glucose elevations, and no gene-dose relationship was observed when comparing maximal glucose increases for cases with -13910C/T and -13910T/T genotypes.

CONCLUSIONS

Genotyping could replace lactose challenge as a first-stage screening test in adults of European descent, but should be used together with tolerance tests in children and patients where secondary lactose intolerance is suspected.