Lactose intolerance: Comparative assessment of diagnostic methods for lactose malabsorption

Background Timely identification of lactose intolerance is crucial to prevent secondary complications. This study aimed to assess the diagnostic accuracy of three commonly used methods for detecting lactose malabsorption (LM): the lactose hydrogen breath test (LHBT), the lactose tolerance test (LTT), and the genetic test (GT). Methods Patients diagnosed with irritable bowel syndrome underwent fasting and post-lactose (20 g) evaluations, including measurements of breath hydrogen, blood glucose, and genotyping for the C/T-13910 polymorphism associated with lactase persistence in European populations. A sustained increase of breath hydrogen ≥20 ppm above baseline, a failure of plasma glucose to rise >20 mg/dL from fasting levels, and the presence of the C/T-13910 variant were defined as positive for LHBT, LTT, and GT, respectively. Results One hundred and eight patients (age 39 ± 14 years, 17 males) were enrolled. Eighty-eight had symptoms after lactose ingestion. Of these, 88 (100%) were LHBT and 69 (78%) were LTT positive. Of a subgroup of 33 patients undergoing GT, 27 presented symptoms and 25 tested positive. Sensitivity and specificity were 100% and 85% for LHBT, 78% and 48% for LTT, and 93% and 83% for GT. Conclusions: With observation times greater than 4 h, LHBT had higher sensitivity and specificity than LTT and GT.