title: A comparison between lactose breath test and quick test on duodenal biopsies for diagnosing lactase deficiency in patients with self-reported lactose intolerance.
abstract: BACKGROUND
  A lactose breath test (LBT) is usually used to diagnose lactase deficiency, and a lactose quick test (LQT) has been proposed as a new test on duodenal biopsies to detect this disorder.
  
  
  OBJECTIVE
  We aimed to assess the diagnostic accuracy of LBT and LQT and their ability to predict the clinical response to a lactose-free diet in patients with self-reported lactose intolerance.
  
  
  METHODS
  Fifty-five patients (age 47 ± 14 y; M/F 15/36) underwent upper gastrointestinal endoscopy and 25g-LBT. Two duodenal biopsies were taken to determine lactase deficiency (normal, mild, or severe) by LQT and to rule out other causes of secondary lactose malabsorption. Patients with a positive LBT and normal LQT also underwent a glucose breath test to exclude small intestinal bacterial overgrowth as a cause of the former result. The severity of gastrointestinal symptoms was measured with a GSS questionnaire, under basal condition and 1 month after a lactose-free diet.
  
  
  RESULTS
  Lactose malabsorption was detected in 31/51 patients with LBT and in 37/51 patients with LQT (P = NS). Celiac disease was found in 2 patients. Two LBT+ patients showed a positive glucose breath test for small intestinal bacterial overgrowth. Eight patients had a mild hypolactasia by LQT and a negative LBT, but they had a significant improvement of symptoms after diet. LQT and LBT were concordant in 83% of cases and predicted the response to a lactose-free diet in 98% and 81% of the cases, respectively (P = 0.03).
  
  
  CONCLUSIONS
  LQT is as sensitive as LBT in detecting lactase deficiency; however, it seems to be more accurate than LBT in predicting the clinical response to a lactose-free diet.
authors.affiliation: Department of Internal Medicine, Gatroenterology Unit, University of Genoa, Genoa, Italy.
authors.forename: Manuele
authors.initials: M
authors.lastname: Furnari
authors.forename: Daria
authors.initials: D
authors.lastname: Bonfanti
authors.forename: Andrea
authors.initials: A
authors.lastname: Parodi
authors.forename: Jolanda
authors.initials: J
authors.lastname: Franzè
authors.forename: Edoardo
authors.initials: E
authors.lastname: Savarino
authors.forename: Luca
authors.initials: L
authors.lastname: Bruzzone
authors.forename: Alessandro
authors.initials: A
authors.lastname: Moscatelli
authors.forename: Francesco
authors.initials: F
authors.lastname: Di Mario
authors.forename: Pietro
authors.initials: P
authors.lastname: Dulbecco
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Savarino
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000378:metabolism; D001706:Biopsy; D001944:Breath Tests; D050528:Diet, Carbohydrate-Restricted; D004386:Duodenum / Q000473:pathology*; D016099:Endoscopy, Gastrointestinal; D005260:Female; D006801:Humans; D043322:Lactase / Q000172:deficiency; D007785:Lactose / Q000378:metabolism*; D007787:Lactose Intolerance / Q000175:diagnosis* / Q000178:diet therapy / Q000201:enzymology / Q000473:pathology; D007789:Lactose Tolerance Test; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011446:Prospective Studies; D057566:Self Report; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D011795:Surveys and Questionnaires; D016896:Treatment Outcome
chemical_list: D015415:Biomarkers; D043322:Lactase; D007785:Lactose