title: Hydrogen breath test for diagnosis of lactose malabsorption: the importance of timing and the number of breath samples.
abstract: BACKGROUND
  The hydrogen breath test (H(2)BT) is the most widely used procedure in the diagnostic workup of lactose malabsorption and lactose intolerance.
  
  
  OBJECTIVE
  To establish whether a simplified two- or three-sample test may reduce time, costs and staff resources without reducing the sensitivity of the procedure.
  
  
  METHODS
  Data from 1,112 patients (292 men, 820 women) with a positive 4 h, nine-sample H(2)BT were retrospectively analyzed. Patients were stratified according to the degree of lactose malabsorption, the occurrence and type of symptoms. Loss of sensitivity in the procedure was evaluated taking into account two-sample tests (0 min and 120 min or 0 min and 210 min) or three-sample tests (0 min, 120 min and 180 min or 0 min, 120 min and 210 min).
  
  
  RESULTS
  Using a two-sample test (0 min and 120 min or 0 min and 210 min) the false-negative rate was 33.4% and 22.7%, respectively. With a three-sample test (0 min, 120 min and 180 min or 0 min, 120 min or 210 min), lactose malabsorption was diagnosed in 91.2% (1,014 of 1,112) patients and in 96.1% (1,068 of 1,112) patients, respectively. Of 594 patients with abdominal symptoms, 158 (26.6%) and 73 (12.2%) would have false-negative results with 0 min and 120 min or 0 min and 210 min two-sample tests, respectively. The three-sample tests, 0 min, 120 min and 180 min or 0 min, 120 min and 210 min, have a false-negative rate of 5.9% and 2.1%, respectively.
  
  
  CONCLUSIONS
  A three-sample H(2)BT is time- and cost-sparing without significant loss of sensitivity for the diagnosis both of lactose malabsorption and lactose intolerance.
authors.affiliation: Dipartimento di Scienze Cliniche, Universita di Roma, La Sapienza, Italy.
authors.forename: Mauro
authors.initials: M
authors.lastname: Di Camillo
authors.forename: Vanessa
authors.initials: V
authors.lastname: Marinaro
authors.forename: Fiorenza
authors.initials: F
authors.lastname: Argnani
authors.forename: Tiziana
authors.initials: T
authors.lastname: Foglietta
authors.forename: Piero
authors.initials: P
authors.lastname: Vernia
mesh_terms: D000328:Adult; D001944:Breath Tests / Q000379:methods; D003937:Diagnosis, Differential; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D006859:Hydrogen / Q000493:pharmacokinetics; D007787:Lactose Intolerance / Q000175:diagnosis* / Q000378:metabolism; D008297:Male; D015203:Reproducibility of Results; D012189:Retrospective Studies; D013997:Time Factors
chemical_list: D006859:Hydrogen