Lactase Deficiency Diagnosed by Endoscopic Biopsy-based Method is Associated With Positivity to Glucose Breath Test

BACKGROUND/AIMS: Lactase deficiency, which has many similarities with small intestinal bacterial overgrowth (SIBO), causes various gastrointestinal symptoms. We estimate the prevalence of SIBO in patients with intestinal symptoms from dairy products and investigate the association between lactase deficiency (LD) and SIBO. METHODS: This prospective study included patients with functional intestinal symptoms from dairy product indigestion. A questionnaire on gastrointestinal symptoms, a hydrogen (H(2))-methane glucose breath test (GBT) for SIBO, and lactose intolerance quick test (LQT) for LD using upper gastrointestinal endoscopy were performed. RESULTS: A total of 88 patients, 29 (33.0%) with severe and 36 (40.9%) with mild LD were included. Sixteen patients (18.2%) were GBT positive. Patients with LQT negativity indicating severe LD showed a higher positivity to GBT or GBT (H(2)) than the historic controls (27.6% vs 6.7%, P = 0.032). There was no difference in the items on the symptom questionnaire according to the presence of LD or SIBO, except for higher symptom scores for urgency in GBT-positive patients. There were more LQT-negative patients in the GBT (H(2))-positive group than in the other groups (27.6% vs 10.2%, P = 0.036). Moreover, only GBT (H(2))-positivity was significantly associated with a higher risk of LQT negativity in multivariate analysis (OR, 4.19; P = 0.029). CONCLUSIONS: SIBO producing H(2) is common in patients with severe LD suspected lactose intolerance. SIBO may be a new therapeutic target for managing intestinal symptoms in patients with lactose intolerance.