P0082 PP A PROSPECTIVE STUDY TO DIAGNOSE ADULT-TYPE HYPOLACTASIA BY CORRELATING RESULTS OF HYDROGEN BREATH TESTING AND DETERMINATION OF LACTASE-NONE PERSISTENCE GENE.

El-Baba, M. F.1; Tolia, V. K.2

Journal of Pediatric Gastroenterology & Nutrition: June 2004 - Volume 39 - Issue - pp S87-S88
ABSTRACTS: Poster Session Abstracts

1Pediatric Gastroenterology and Nutrition, Children’s Hospital of Michigan, 2Pediatric Gastroenterology and Nutrition, Children’s Hospital of Michigan, Detroit, United States

Submitted by: melbaba@med.wayne.edu

Article Outline

Introduction: Adult primary lactase deficiency also known as lactase non-persistence is a common autosomal recessive condition that can give rise to symptoms mainly in adolescents and early childhood. Lactose breath hydrogen test (BHT) is used most commonly for the diagnosis of lactose malabsorption. Recent studies have shown that the DNA variant C/C-13910 located upstream from the LCT locus is associated with lactase nonpersistence due to a defect in the expression of the lactasephlorizin hydrolase. We conducted a prospective study to diagnose lactose intolerance by correlating results of genetic testing for the C/T-13910 variant and lactose BHT.

Methods: 26 patients (15 females, 10 males, mean age 10.7yr) seen in the Gastroenterology clinic at Children’s Hospital of Michigan for possible lactose intolerance were tested by standard BHT after ingestion of 2 gram/Kg lactose (maximum 25 gm). Same patients were also tested for presence of the C/T-13910 variant using specific restriction enzyme digest assays (Prometheus Laboratories) at the time of blood draw for routine laboratories.

Results: (Table 1). Ten patients had a positive hydrogen test, and 16 were negative. C/C-13910 variant was detected in all patients with positive BHT. Three patients had a negative BHT but positive gene test. Those three patient showed arise in breath hydrogen concentration but was <10 PPM over baseline, and none reported any symptoms after lactose ingestion Thirteen patients were negative for both BHT and gene tests. Based on these data, positive predictive value, negative predictive value, sensitivity and specificity of gene test compared to lactose BHT were 77%, 100%, 100% and 81% respectively.

Conclusion: Analysis of T/C-13910 variant is a reliable test to diagnose adult-onset hypolactasia with a high certainty for the rule out of genetically based lactose intolerance syndrome. However, further studies are needed in this ongoing study to understand the reliability of genetic testing in low- or non-hydrogen producers.

Financial Disclosure (put None if not applicable): None

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Reference(S):

Enattah NS, et al. Identification of a variant associated with adult-type hypolactasia. Nat Genet. 2002;30(2):233–7
Jarvela I, et al. Assignment of the locus for congenital lactase deficiency to 2q21, in the vicinity of but separate from the lactasephlorizin hydrolase gene. Americ J of Human Genet 1998;63(4): 1078–85
© 2004 Lippincott Williams & Wilkins, Inc.