Prevalence of lactase persistence and the performance of a new non invasive genetic test in adult Sardinian patients

Background & aims: Adult-type hypolactasia is a common problem in humans. In the clinical setting, the breath hydrogen test is frequently used to measure lactose nonabsorption; however, false results can occur. The prevalence of genetic lactase persistence in Sardinia and the performance of a new noninvasive genetic test based on the presence of C/T-13910 polymorphism were evaluated. Methods: Saliva was collected from adult patients undergoing breath hydrogen test and from a control group of healthy subjects. DNA was analyzed for C/T-13910 and four additional mutations nearby. Results: One hundred and twenty patients and 120 controls were enrolled. In the patient group, the frequency of the C/C-13910 (homozygous genotype for lactase non-persistence) was 89.2%; the C/T (heterozygosity for lactase persistence) was 10.8%; and the T/T (homozygous for lactase persistence) was 0. The frequency for C/C, C/T, T/T was 78.3%, 21.7%, and 0, respectively, in the control group. The sensitivity, specificity and accuracy of the breath hydrogen test compared to the genetic test were 86.1%, 92.3%, and 87.5%, respectively. The concordance of the results of the two tests was highly significant (p < 0.0001). Conclusions: Mutants for lactase persistence are very uncommon in Sardinia. Simplicity of genotyping 13910 C/T to assess the lactase non-persistence should make this method suitable for routine clinical testing when lactose malabsorption is suspected.