Frequency and Diagnostic Utility of the −13910C>T MCM6 Gene Polymorphism for Lactose Intolerance in a Brazilian Northeast Population

Background/Aim: Lactose intolerance (LI) is a common clinical condition associated with reduced lactase enzyme activity. The oral lactose tolerance test (OLTT), although widely used for diagnosis, has several limitations such as fasting, multiple blood collections, and gastrointestinal discomfort. As an alternative, genetic testing targeting the −13910C>T polymorphism in the MCM6 gene, a regulator of lactase expression, has gained prominence as it is non-invasive, rapid, and unaffected by physiological variation. This study aimed to evaluate the frequency of the −13910C>T polymorphism of the MCM6 gene in the population of Fortaleza and compare the genotyping results with the OLTT, to verify its diagnostic applicability. Materials and Methods: A descriptive study was conducted with data from 2359 patients examined between January 2022 and May 2025 at a private laboratory. Concordance between genotyping and OLTT was analyzed in 24 patients who underwent both tests, with OLTT considered the reference standard. Sensitivity, specificity, accuracy, and Kappa coefficient were calculated. All analyses were performed using R software. Results: The median age of participants was 7 years (range=0.06-100 years). The observed genotype frequencies were 52.90% for the CC genotype, 38.74% for CT, and 8.35% for TT. The Kappa test demonstrated moderate agreement between the genetic test and OLTT [k=0.583 (p=0.00413)], with a sensitivity of 81.82% [95% confidence interval (CI)=48.22-97.71], overall accuracy of 79.17%, and specificity of 76.92% (95%CI=48.16-94.96). Conclusion: Genotyping for the −13910C>T polymorphism in the MCM6 gene represents a promising diagnostic alternative for lactose intolerance, offering a feasible and less invasive approach with good sensitivity and specificity.