title: A diagnostic approach to patients with suspected lactose malabsorption.
abstract: BACKGROUND
  The lactose breath test (LBT) is the standard technique for diagnosis of lactose malabsorption. However, it is time-consuming, strenuous for the patient and has been reported to have low sensitivity. The lactose intolerance quick test (LIQT) measures lactase activity in duodenal biopsies and may be performed as part of upper gastrointestinal endoscopy.
  
  
  OBJECTIVE
  The purpose of this study was to assess the role of the LBT and LIQT in the case management of suspected lactose malabsorption.
  
  
  METHODS
  The study group included 69 consecutive patients evaluated by the LBT followed by the LIQT. The test results were compared, and the sensitivity, specificity, and predictive values of the LBT were calculated.
  
  
  RESULTS
  Mean age of the patients was 54.4 years, male/female ratio was 1:3, and mean body mass index was 25.2. None had celiac disease on duodenal biopsy. The LIQT was positive for hypolactasia in 55 patients (80 %): mild in 14 (25 %) and severe in 41 (75 %); 10 (18 %) were symptomatic during the LBT. The LBT was positive for lactose malabsorption in 32 patients (46 %). Of the 37 patients with normal findings on the LBT, 24 (65 %) had positive findings on the LIQT: 11 (30 %) mild hypolactasia, 13 (35 %) severe hypolactasia. In one case, the LBT was positive and the LIQT was negative. The LBT had a sensitivity of 56 %, specificity 93 %, positive predictive value 97 %, and negative predictive value 35 %.
  
  
  CONCLUSIONS
  The LBT may serve as a diagnostic screening tool for lactose malabsorption. Symptomatic patients with negative LBT results should be referred for second-line testing with the LIQT.
authors.affiliation: Laboratory of Gastroenterology, Rabin Medical Center, Beilinson Campus, Petach Tikva, Israel.
authors.forename: Tsachi Tsadok
authors.initials: TT
authors.lastname: Perets
authors.forename: Einav
authors.initials: E
authors.lastname: Shporn
authors.forename: Shoshana
authors.initials: S
authors.lastname: Aizic
authors.forename: Elena
authors.initials: E
authors.lastname: Kelner
authors.forename: Sigal
authors.initials: S
authors.lastname: Levy
authors.forename: Yifat
authors.initials: Y
authors.lastname: Bareli
authors.forename: Lea
authors.initials: L
authors.lastname: Pakanaev
authors.forename: Yaron
authors.initials: Y
authors.lastname: Niv
authors.forename: Ram
authors.initials: R
authors.lastname: Dickman
mesh_terms: D001706:Biopsy; D001944:Breath Tests / Q000379:methods*; D004386:Duodenum / Q000201:enzymology* / Q000473:pathology; D005260:Female; D006801:Humans; D043322:Lactase / Q000378:metabolism*; D007787:Lactose Intolerance / Q000175:diagnosis*; D008297:Male; D008875:Middle Aged
chemical_list: D043322:Lactase