Editing Lactose intolerance (section)

=== Intestinal biopsy ===
An intestinal biopsy must confirm lactase deficiency following discovery of elevated hydrogen in the hydrogen breath test.<ref name="Berdanier">{{cite book | last1 = Hargrove | first1 = James L. | last2 = Berdanier | first2 = Carolyn D. |title=Nutrition and gene expression |publisher=CRC Press |location=Boca Raton |year=1993 |isbn=978-0-8493-6961-2 }}{{page needed|date=June 2018}}</ref>  Modern techniques have enabled a bedside test, identifying presence of lactase enzyme on upper gastrointestinal endoscopy instruments.<ref>{{cite journal | vauthors = Kuokkanen M, Myllyniemi M, Vauhkonen M, Helske T, Kääriäinen I, Karesvuori S, Linnala A, Härkönen M, Järvelä I, Sipponen P | title = A biopsy-based quick test in the diagnosis of duodenal hypolactasia in upper gastrointestinal endoscopy | journal = Endoscopy | volume = 38 | issue = 7 | pages = 708–12 | date = July 2006 | pmid = 16761211 | doi = 10.1055/s-2006-925354 | s2cid = 260130448 }}</ref>  However, for research applications such as [[mRNA]] measurements, a specialist laboratory is required.