Diagnosis of lactose intolerance: concordance between 13910-C/T genotype and lactose tolerance test in a Danish population.

The association between the MCM6-13910-C/T polymorphism and lactose intolerance in individuals of European descent is well known. However, the notion that having a single versus a double allelic mutation might influence one's phenotype has been hypothesized. This study investigated whether patients with the three genotypes C/C, C/T, T/T differed in response to a lactose tolerance test (LTT) in a Danish setting. Anonymized data on 603 individuals with results for both genetic test and LTT were investigated. Mean delta glucose values were plotted for the time points of the LTT (0, 15, 30, 45 and 60 min) for the C/C, C/T and T/T genotype, respectively. Further, the agreement between the three genotypes and the diagnostic interpretation of the LTT were examined using a cut-off of > 1.4 mmol/L rise in glucose. In subjects with the C/C genotype, mean glucose delta levels were markedly lower compared to both the C/T and T/T genotypes at all time points. Overall, a difference between mean glucose delta values among the C/T and T/T genotype could not be shown. Using a LTT cut-off of > 1.4 mmol/L, the proportions of lactose intolerant LTT results for each genotype were as follows: 58% among C/C, 5% among C/T, and 7% among T/T. In a Danish healthcare setting, the C/C genotype was on average associated with a smaller glucose response during a LTT when compared to the C/T and T/T genotypes. A marked difference in the LTT response among the C/T and T/T genotype was not observed.