title: Hydrogen breath test for the diagnosis of lactose intolerance, is the routine sugar load the best one?
abstract: OBJECTIVE
  To evaluate the prevalence of lactose intolerance (LI) following a load of 12.5 g in patients diagnosed as high-grade malabsorbers using the hydrogen breath test (HBT)-25.
  
  
  METHODS
  Ninety patients showing high-grade malabsorption at HBT-25 were submitted to a second HBT with a lactose load of 12.5 g. Peak hydrogen production, area under the curve of hydrogen excretion and occurrence of symptoms were recorded.
  
  
  RESULTS
  Only 16 patients (17.77%) with positive HBT-25 proved positive at HBT-12.5. Hydrogen production was lower as compared to HBT-25 (peak value 21.55 parts per million (ppm) +/- 29.54 SD vs 99.43 ppm +/- 40.01 SD; P < 0.001). Symptoms were present in only 13 patients. The absence of symptoms during the high-dose test has a high negative predictive value (0.84) for a negative low-dose test. The presence of symptoms during the first test was not useful for predicting a positive low-dose test (positive predictive value 0.06-0.31).
  
  
  CONCLUSIONS
  Most patients with a positive HBT-25 normally absorb a lower dose of lactose and a strict lactose restriction on the basis of a "standard" HBT is, in most instances, unnecessary. Thus, the 25 g lactose tolerance test should probably be substituted by the 12.5 g test in the diagnosis of LI, and in providing dietary guidelines to patients with suspected lactose malabsorption/intolerance.
authors.affiliation: Gastroenterologia A e Scienza dell'Alimentazione, Sapienza Università di Roma, Roma 00161, Italy.
authors.forename: Fiorenza
authors.initials: F
authors.lastname: Argnani
authors.forename: Mauro
authors.initials: M
authors.lastname: Di Camillo
authors.forename: Vanessa
authors.initials: V
authors.lastname: Marinaro
authors.forename: Tiziana
authors.initials: T
authors.lastname: Foglietta
authors.forename: Veronica
authors.initials: V
authors.lastname: Avallone
authors.forename: Carlo
authors.initials: C
authors.lastname: Cannella
authors.forename: Piero
authors.initials: P
authors.lastname: Vernia
mesh_terms: D000284:Administration, Oral; D001944:Breath Tests; D006801:Humans; D006859:Hydrogen / Q000378:metabolism*; D007785:Lactose / Q000008:administration & dosage / Q000493:pharmacokinetics; D007787:Lactose Intolerance / Q000175:diagnosis* / Q000378:metabolism; D007789:Lactose Tolerance Test; D011237:Predictive Value of Tests
chemical_list: D006859:Hydrogen; D007785:Lactose