Hypersensitivity to the Lactulose Nutrient Challenge Test in Irritable Bowel Syndrome: A Noninvasive Test of...

Patients with irritable bowel syndrome (IBS) often experience meal-related symptoms, which might be related to visceral hypersensitivity. The lactulose nutrient challenge test (LNCT) is a noninvasive measure of sensitivity in relation to a meal. We aimed to define a cut-off for hypersensitivity to LNCT based on results in healthy volunteers, and to characterize patients with LNCT hypersensitivity.

Patients with IBS (n = 273) and healthy volunteers (n = 133) who completed LNCT were included. During LNCT, 8 symptoms are rated on Likert scales and breath hydrogen/methane is assessed every 15 minutes for 4 hours. Additional questionnaires assessed severity of gastrointestinal (GI), somatic, and psychological symptoms. A subset completed oro-anal transit time and rectal sensitivity investigations. LNCT hypersensitivity was defined based on the average area under the curve of healthy volunteers (95th percentiles) for abdominal pain, bloating, and gas/flatulence. Statistics included univariate and logistic regression (odds ratio [95% confidence interval]) analyses.

In total, 76% of patients with IBS were hypersensitive to LNCT. These patients had distinct characteristics because they were more frequently female, reported more severe GI, non-GI somatic, and psychological symptoms and had higher breath hydrogen production and lower rectal pain thresholds. More severe GI symptoms (2.05 [1.05-3.99]), lower rectal pain threshold (0.93 [0.88-0.99]), and higher breath hydrogen production (1.14 [1.02-1.29]) were identified as independent predictors of hypersensitivity to LNCT.

The LNCT is useful as a noninvasive and physiologic tool to test GI sensory function in relation to a meal. Moreover, overall GI symptom reporting, visceral hypersensitivity, and hydrogen production are important factors involved in postprandial symptoms in IBS.