Lactase persistence/non-persistence variants, C/T_13910 and G/A_22018, as a diagnostic tool for lactose intolerance in IBS patients.
BACKGROUND
Irritable bowel syndrome (IBS) is a symptom-based disorder characterized by abdominal pain related to altered bowel habit. We evaluated the predictive power of 2 genetic markers of hypolactasia, C/T_13910 and G/A_22018, in IBS patients with and without lactose intolerance in order to gain insight into the role of lactose intolerance in IBS.


METHODS
Seventy five patients (59F/16M, mean age: 49.6+/-14.2 years) with an IBS diagnosis based on Rome II criteria and 272 healthy individuals, where 74 (58F/16M, 54.1+/-10.9 years) were matched-controls, were evaluated. IBS and healthy individuals were genotyped for the C/T_13910 and G/A_22018 polymorphisms nearby the lactase-phlorizin hydrolase gene. Hydrogen breath test (HBT) with gas chromatography was performed in IBS patients to assess for lactose intolerance.


RESULTS
Of the 75 IBS patients, 28 (37%) were defined as lactose intolerants. The grade/severity of symptoms after an oral lactose load were positively correlated to the expiratory H2 excretion (P<0.001). Alleles and genotypes frequencies from C/T_13910 and G/A_22018 were not significantly different between IBS patients and control individuals (P>0.05;NS). Presence of the C and G allele were positively associated with a higher expiratory hydrogen excretion and more intense gastrointestinal symptoms (P<0.001). Considering these polymorphisms as a diagnostic test for lactose intolerance in IBS patients, presence of the CC and GG genotypes were estimated to have, a sensitivity of 100% and 96%, respectively; and a specificity of 83% and 79%, positive predictive value of 76% and 73%, and negative predictive value of 100% and 97%.


CONCLUSIONS
In IBS patients, genotyping of C/T_13910 and G/A_22018 polymorphisms predicts gastrointestinal symptoms after lactose ingestion and are a diagnostic tool for lactose intolerance.
Bernardes-Silva
Carlos Felipe
CF
Department of Gastroenterology - University of São Paulo School of Medicine, São Paulo, SP, Brazil. carlosfelipebs@uol.com.br
Pereira
Alexandre C
AC
de Fátima Alves da Mota
Glória
G
Krieger
José Eduardo
JE
Laudanna
Antonio Atílio
AA
D000328:Adult; D000483:Alleles; D001944:Breath Tests / Q000379:methods; D002849:Chromatography, Gas; D005260:Female; D005838:Genotype; D006801:Humans; D006859:Hydrogen / Q000032:analysis; D043183:Irritable Bowel Syndrome / Q000473:pathology*; D043322:Lactase / Q000235:genetics*; D010694:Lactase-Phlorizin Hydrolase / Q000235:genetics*; D007787:Lactose Intolerance / Q000175:diagnosis* / Q000453:epidemiology / Q000235:genetics; D007789:Lactose Tolerance Test; D008297:Male; D008875:Middle Aged; D016269:Milk Hypersensitivity / Q000175:diagnosis; D011110:Polymorphism, Genetic; D011237:Predictive Value of Tests; D013997:Time Factors
D006859:Hydrogen; D043322:Lactase; D010694:Lactase-Phlorizin Hydrolase