Correlation between Symptoms and Gas Production in Lactose Intolerant Subjects. Can Symptoms Predict a Diagnosis of Lactose Intolerance?

Purpose: To correlate intestinal gas production with the intensity of symptoms experienced during a lactose breath test (LBT) and to evaluate the value of different symptoms in lactose malabsorption diagnosis as assessed by LBT, considered as the gold standard. Design: A statistical correlation between symptoms and gas production, and the prevalence of symptoms in consecutive patients screened for lactose malabsorption. Materials and Methods: All symptoms and their intensity during a 5 hour breath test after a 20 g oral lactose dose were recorded in 214 patients. A symptom score was calculated and correlated to the gases measured in expired air. Results: The most frequently experienced symptoms were: bloating in 70.3% of patients with a pathological breath test and in 22.3% of patients with a normal breath test ( p < 0.0005, odds ratio = 7.7); abdominal pain in 34.7% of patients with a pathological breath test and in 18.7% of patients with a normal breath test ( p = 0.009, odds ratio = 2.7); headache in 11.9% of patients with a pathological breath test and in 9.4% of patients with a normal breath test ( p = 0.3); nausea in 8.5% of patients with a pathological breath test and in 5.2% of patients with a normal breath test ( p = 0.3); diarrhoea in 9.3% of patients with a pathological breath test and in 5.2% of patients with a normal breath test ( p = 0.2). There was a low but significant correlation between hydrogen (H 2 ) production and symptoms ( r = 0.37, p < 0.000005), but we found no correlation between methane (CH 4 ) production and symptoms. Bloating appearing within 5 hours after an oral lactose dose had a positive predictive value of 79% and a negative predictive value of 68% in breath test results. Conclusions: Our results show that only H 2 but not CH 4 production correlates with symptoms after a 20 g lactose dose. A possible interpretation of these results is that the generation of symptoms is a complex process that involves not only gases but other... [ABSTRACT FROM AUTHOR]