title: Excellent agreement between genetic and hydrogen breath tests for lactase deficiency and the role of extended symptom assessment.
abstract: Clinical manifestations of lactase (LCT) deficiency include intestinal and extra-intestinal symptoms. Lactose hydrogen breath test (H2-BT) is considered the gold standard to evaluate LCT deficiency (LD). Recently, the single-nucleotide polymorphism C/T(-13910) has been associated with LD. The objectives of the present study were to evaluate the agreement between genetic testing of LCT C/T(-13910) and lactose H2-BT, and the diagnostic value of extended symptom assessment. Of the 201 patients included in the study, 194 (139 females; mean age 38, range 17-79 years, and 55 males, mean age 38, range 18-68 years) patients with clinical suspicion of LD underwent a 3-4 h H2-BT and genetic testing for LCT C/T(-13910). Patients rated five intestinal and four extra-intestinal symptoms during the H2-BT and then at home for the following 48 h. Declaring H2-BT as the gold standard, the CC(-13910) genotype had a sensitivity of 97% and a specificity of 95% with a κ of 0.9 in diagnosing LCT deficiency. Patients with LD had more intense intestinal symptoms 4 h following the lactose challenge included in the H2-BT. We found no difference in the intensity of extra-intestinal symptoms between patients with and without LD. Symptom assessment yielded differences for intestinal symptoms abdominal pain, bloating, borborygmi and diarrhoea between 120 min and 4 h after oral lactose challenge. Extra-intestinal symptoms (dizziness, headache and myalgia) and extension of symptom assessment up to 48 h did not consistently show different results. In conclusion, genetic testing has an excellent agreement with the standard lactose H2-BT, and it may replace breath testing for the diagnosis of LD. Extended symptom scores and assessment of extra-intestinal symptoms have limited diagnostic value in the evaluation of LD.
authors.affiliation: Division of Gastroenterology and Hepatology, University Hospital Zurich, Raemistrasse 100, 8091 Zürich, Switzerland. daniel.pohl@usz.ch
authors.forename: D
authors.initials: D
authors.lastname: Pohl
authors.forename: E
authors.initials: E
authors.lastname: Savarino
authors.forename: M
authors.initials: M
authors.lastname: Hersberger
authors.forename: Z
authors.initials: Z
authors.lastname: Behlis
authors.forename: B
authors.initials: B
authors.lastname: Stutz
authors.forename: O
authors.initials: O
authors.lastname: Goetze
authors.forename: A V
authors.initials: AV
authors.lastname: Eckardstein
authors.forename: M
authors.initials: M
authors.lastname: Fried
authors.forename: R
authors.initials: R
authors.lastname: Tutuian
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001944:Breath Tests / Q000379:methods*; D005260:Female; D005820:Genetic Testing / Q000379:methods*; D005838:Genotype; D006801:Humans; D006859:Hydrogen; D007410:Intestinal Diseases / Q000209:etiology*; D043322:Lactase / Q000172:deficiency / Q000235:genetics; D007785:Lactose / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D020641:Polymorphism, Single Nucleotide; D015203:Reproducibility of Results; D012720:Severity of Illness Index; D055815:Young Adult
chemical_list: D006859:Hydrogen; D043322:Lactase; D007785:Lactose