Lactose intolerance genetic testing: Is it useful as routine screening? Results on 1426 south–central Italy patients

Abstract

Adult-type hypolactasia is a widespread condition throughout the world, causing lactose malabsorption. Several studies suggested that the identification of C/T-13910 and G/A-22018 mutations, located upstream the gene encoding the lactase-phlorizin hydrolase (LPH), is a useful tool for the differential diagnosis of hypolactasia. We evaluated the frequencies of C/T-13910 and G/A-22018 variants in a central–south Italian population and the usefulness of lactase deficiency genetic testing in the clinic practice. The genomic DNA of 1426 patients and 1000 healthy controls from central–south Italy was isolated from peripheral whole blood and genotyped for the C/T-13910 and G/A-22018 polymorphisms by high-resolution melting analysis (HRMA) and sequencing. The frequencies of genotypes in the 1426 patients analysed were as follows: 1077 CC/GG (75.5%), 287 CT/GA (20.1%), 24 TT/AA (1.7%), 38 CC/GA (2.7%). Only 64 out of 1426 (4.5%) performed also L-BHT test, 29 of which were negative for L-BHT also in presence of different genotypes. Among the 35 individuals with L-BHT positive, 34 were CC/GG and only one CT/GA. Although lactose genetic test is a good predictor of persistence/non-persistence lactase in specific population, its use in the central–south Italy population should be limited given the high prevalence of the CCGG diplotype in normal individuals.