Correlation between symptoms developed after the oral ingestion of 50 g lactose and results of hydrogen breath testing for lactose intolerance

Background Lactase deficiency is a common condition responsible for various abdominal symptoms. Lactose hydrogen breath test is currently the gold standard in diagnosing lactose intolerance. Aim To assess sensitivity and specificity of symptoms developed after oral lactose challenge. Methods Intensity of nausea, abdominal pain, borborygmi, bloating and diarrhoea was recorded every 15 min up to 3 h after ingestion of 50 g lactose in patients with positive (i.e. breath H2-concentration >= 20 p.p.m. above baseline) and negative lactose hydrogen breath test. Results Between July 1999 and December 2005, 1127 patients (72% females) underwent lactose hydrogen breath test. A positive result was found in 376 (33%). Sensitivity of individual symptoms ranged from 39% (diarrhoea) to 70% (bloating) while specificity ranged from 69% (bloating) to 90% (diarrhoea). A positive lactose hydrogen breath test was found in 21% of patients with one symptom, 40% of patients with two symptoms, 44% of patients with three symptoms, 67% of patients with four symptoms and 82% of patients with five symptoms. Symptom intensity was significantly higher for each symptom in the positive group. Conclusions Evaluating symptoms developed after ingestion of 50 g lactose can be used as a simple screening test to select patients who need to be referred for lactose intolerance testing.