Background: Symptoms associated with lactose intolerance (LI) and
diarrhea-predominant irritable bowel syndrome (IBS-D) are almost the
same. These disease entities are difficult to differentiate clinically.
In practice, differential diagnosis depends on self-reported patient
milk intolerance. However, there is limited data on the prevalence of
LI in China. The aim of this study was to investigate the prevalence of
LI in IBS-D patients and asymptomatic healthy controls. Methods:
Lactose malabsorption (LM) was diagnosed by a lactose hydrogen breath
test (HBT) and was defined by peak breath H2 excretion over the
baseline level of 65 20 ppm. LI-related symptoms were monitored
for 8 h following lactose administration. LI was defined in LM patients
with positive symptoms during the observation time. Patients with IBS-D
were additionally asked if they were intolerant to milk. Results: A
total of 109 eligible IBS-D patients (Rome III criteria) and 50 healthy
controls were enrolled in this study. Except for hydrogen
non-producers, the prevalence of LM did not differ between IBS-D
patients and the control group (85%, 82/96 vs 72%, 34/47; P = 0.061).
There was, however, a higher LI prevalence in IBS patients than in
healthy subjects (45%, 43/96 vs 17%, 8/47; P = 0.002). Sensitivity,
specificity, and positive and negative predictive values of
self-reported milk intolerance for detecting LI were 58, 58, 53, and
63%, respectively. Conclusions: Prevalence of LI is significantly
higher in IBS-D patients than in healthy subjects. Self-reported milk
intolerance is a poor diagnostic predictor of LI