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Adult-type hypolactasia (primary lactose malabsorption) affects most of world's human population and limits the use of fresh milk due to lactose intolerance. The diagnosis of adult-type hypolactasia has been difficult to establish because of unsatisfactory diagnostic methods. C/T(-13910) single nucleotide polymorphism residing 13910 base pairs from the 5' end of the lactase gene has been shown to be associated with lactase persistence. The aim of the study was to assess the applicability of the C/T(-13910) variant as a diagnostic test for adult-type hypolactasia during childhood.Intestinal biopsies were obtained from 329 children and adolescents of African, Finnish, and other White origins aged 0.1-20 years undergoing upper gastrointestinal endoscopy because of abdominal complaints. The biopsies were assayed for lactase, sucrase, and maltase activity and genotyped for the C/T(-13910) variant using polymerase chain reaction minisequencing.The frequency of the C/C(-13910) genotype defining lactase non-persistence was well in agreement in this study with published figures for the prevalences of adult-type hypolactasia in Africans and Whites. The C/C(-13910) genotype was associated with very low lactase activity (10 U/g protein) in the majority of children tested at 8 years of age and in every child older than 12 years of age giving a specificity of 100% and sensitivity of 93% for the genetic test. The decline of lactase activity was somewhat earlier in African compared with Finnish children with C/C(-13910) genotype (p0.03).Genetic test of C/T(-13910) polymorphism can be used as a first stage screening test for adult-type hypolactasia.

Adult-type hypolactasia, characterised by bloating, gas formation, and diarrhoea after ingestion of lactose containing food, affects half of the world’s population.1 The molecular background of lactase non-persistence/persistence trait has been shown to associate with a single nucleotide polymorphism (SNP) C/T−13910 residing 13910 base pairs upstream from the 5′ end of the lactase (LCT) gene in an intron of the minichromosome maintenance 6 (MCM6) gene.2–4 We have demonstrated a trimodal distribution of lactase activity in the intestinal mucosa in adults, with low lactase activity (4–9 U/g protein) in those with the C/C−13910 genotype.3 The C−13910 and T−13910 allele show differential regulation of lactase promoter activity and binding capacity for the nuclear proteins in electromobility shift assay.5,6 Our recent analysis in a paediatric population demonstrated that the main time period for lactase downregulation in Finns and in Somalians is from five to 10 years of age.4 To further assess the role …