Comparison of a Real-Time Polymerase Chain Reaction Assay for Lactase Genetic Polymorphism With Standard Indirect Tests for Lactose Maldigestion

Andrew Szilagyi, Paula Malolepszy, Elise Hamard, Xiaoqing Xue, Nir Hilzenrat, Mary Ponniah, Elizabeth MacNamara, George Chong

Research output: Contribution to journalArticlepeer-review

27 Scopus citations

Abstract

Background & Aims: There is a discrepancy in outcome between the lactose tolerance and breath hydrogen tests for lactose maldigestion. The availability of a validated genetic test for lactase polymorphism allows a reevaluation of these tests. Methods: Thirty healthy adults participated in a 50-g lactose challenge test at a university clinic. Blood was drawn for genetic and timed blood glucose testing (2 hours), and breath hydrogen was measured (4.5 hours). Lactase genetic polymorphism was assessed by a real-time polymerase chain reaction assay. Participants completed a diet questionnaire, and symptoms were recorded during the lactose challenge. Sensitivity and specificity were calculated for each indirect test. The 2-way kappa coefficient between these tests was evaluated. Student t test and Wilcoxon rank sum test were used to compare variables. Results: The lactose tolerance test as a standard had an 87.5% sensitivity and 92.7% specificity for genetic status. Only a moderate agreement between lactose tolerance test and breath hydrogen test was observed (2-way kappa coefficient, .53; 95% confidence interval, .22-.83). When genetic status was used as standard, symptoms had a moderate sensitivity and specificity. Lactose tolerance test had very good sensitivity, and the breath test had excellent specificity. Conclusions: Both indirect tests independently have good to very good sensitivities and specificities for genetic lactase status. The noted disagreement likely reflects variables that affect the tests independently of intestinal lactase status. The value of these tests in the light of the availability of genetic testing is discussed.

Original languageEnglish
Pages (from-to)192-196
Number of pages5
JournalClinical Gastroenterology and Hepatology
Volume5
Issue number2
DOIs
StatePublished - 1 Feb 2007
Externally publishedYes

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