Objective: To reevaluate the timing and level of rise in breath hydrogen (H2) excretion following oral lactose challenge in children with respect to the subsequent development of symptoms consistent with lactose intolerance.
Methods: Breath hydrogen test (BHT) data from 581 individuals < 19 yr of age (mean age 7.4 yr), all of whom had a fasting baseline breath H2 concentration of < 20 ppm, were reviewed. All subjects ingested 2 g/kg lactose (maximum 50 g) and had breath H2 analysis at 30-min intervals for 3 h. Symptoms of abdominal pain, bloating, gas, and diarrhea were monitored.
Results: Seventeen percent of subjects had no H2 detectable in their breath at any time, 41% had a rise < 10 ppm from baseline, 6% increased 10-19 ppm, and 36% had a rise > or = 20 ppm. Symptom development (gas, bloating, abdominal pain, diarrhea) was similar in the non-H2 excretors, the delta < 10 ppm, and the delta 10-19 ppm groups. Compared to the < 10 ppm or < 20 ppm groups, subjects with a rise of > or = 20 ppm were more likely to develop diarrhea (p < 0.0001), gas (p < 0.0001), bloating (p < 0.0001), and abdominal pain (p < 0.0001). Symptoms were more common in the > or = 20 ppm group than in the delta 10-19 ppm group (p < 0.02 for diarrhea, p < 0.0001 for gas, bloating, and abdominal pain). Fifty-three percent of subjects with a rise in breath H2 < 20 ppm reported symptoms during or after the BHT, and 9% of those with a rise > or = 20 ppm were asymptomatic.
Conclusion: A rise of breath H2 concentration of > or = 20 ppm over baseline appears to correlate better with subsequent symptom development than does > or = 10 ppm. However, the frequently poor association between symptoms of lactose intolerance and breath H2 excretion suggest caution in the interpretation of the clinical significance of the BHT.