Early peak of hydrogen during lactose breath test predicts intestinal motility

Abstract

Lactose breath test (LBT) is considered the gold standard for the diagnosis of lactose malabsorption. The test is considered positive for a peak of hydrogen (H 2 ) ≥ 20 parts per million (ppm) above the baseline. Some patients (pts) showed a rapid peak between 30 and 90 minutes after lactose ingestion. The aim of this study was to evaluate the predictive value of an early peak during a LBT and an accelerated oro-cecal transit time (OCTT). We retrospectively analyzed all pts who referred to our Gastroenterology unit for Irritable Bowel Syndrome, from January to September 2012, who performed LBT, glucose and lactulose breath test. We consider a positive LBT for a peak of H 2 > 20 ppm, a positive GHBT for a peak >12 ppm and we considered a normal OCCT a peak of H 2 ≥ 10 ppm between 75 ± 105 min after lactulose load. The correlation between LBT and OCTT was evaluated by Pearson score. 93 pts (65 F/28 M mean age 47 ± 6 years) with a positive LBT, without small intestinal bacterial overgrowth were analyzed: 46 pts (32 F/14 M; mean age 48 ± 6 years) with an early peak (<90 min) of H 2 (≥20 ppm) were enrolled as case, and 47 pts matched for sex and age with a peak of H 2 after 90 min were enrolled as controls. 72% (33/46) of the group with an early peak showed an accelerated, 17% (8/46) a normal and 11% (5/46) a delayed OCTT. Meanwhile, in control group 40.4% (19/47) showed a normal, 57.5% (27/47) a delayed and just 1 pts an accelerated OCTT. The specificity and sensibility of LBT for an accelerated OCTT were 97.9% and 71.7% respectively. The positive predictive value of LBT for an accelerated OCTT is 97.1%; the negative predictive value is 78%. There is a significant correlation between LBT and OCTT (p < 0.05). The presence of an early peak of H 2 between 30 and 90 min after the ingestion of 25 gr of lactose could predict the presence of an accelerated OCTT in 97% of pts. If confirmed by further study, in this subset of pts, lactulose breath test for evaluating OCTT could be avoided.