Background: Lactose intolerance afflicts 5-10% of the population in western Europe, but is very common (up to 90%) in the southern hemisphere. Traditional analysis methods are based on lactose intake followed by determination of blood glucose concentration or exhaled H 2 and CH 4 . In many diagnostic laboratories, single nucleotide polymorphism (SNP) analysis on C/T-13910 has been introduced as a replacement for the traditional lactose intolerance testing. Homozygozity for the C-allele of this SNP results in very low or absent lactase enzyme activity. We have compared our present routine test (blood glucose measurements) to genetic SNP testing for C/T-13910.
Material and methods: Blood glucose measurements (after intake of lactose) and genotyping of C/T-13910 were performed on 137 adult participants after they had given informed consent. The maximal difference from fasting blood glucose was compared with real-time PCR analysis of C/T-13910.
Results and interpretation: Lactose intolerance using blood glucose was positive for 20.4% of those tested; for the genetic test the corresponding result was 17.5%. The correlation between the methods was strong (90%) with a kappa-statistics index of 0.67 (0.51 - 0.83, 95% CI). Our results indicate that the genetic test for C/T-13910 complements the traditional phenotype measurements.