Table 4

Brief characterisation of the diagnostic tests available for lactose malabsorption

Hydrogen breath testLactose tolerance testDuodenal lactase activitySerum gaxilose or urine galactose testGenetic test
Lactose challengeYesYesNoYes (gaxilose)No
Assessment of symptoms and LIYes/possibleYes/possibleNo/not possibleNo/not possibleNo/not possible
Test principleDetection of H2 in expiratory airIncrease in plasma glucose after lactose challengeLactase enzymatic activity in duodenal biopsyDetection of D-xylose in serum or Galactose in urine after cleavage of orally administered 4-galactosylxylose (gaxilose) by lactaseDetection of −13910 C/T polymorphism
Detection of secondary LMYesYesYesYesNo
CostsLowLowestHigh (if costs for endoscopy are included)IntermediateHigh
LimitationsFalse-negative tests by H2-non- producer. False-positive tests with SIBO, rapid transit, altered bowel anatomyDisorders of glucose metabolism, altered bowel anatomyPatchy expression of lactaseVariable test performance in literature. False-positive tests with SIBO, rapid transit and other conditionsFalse negative in the presence of atypical mutations (relevant in non-Caucasian populations)
Best useTest of choice to assess LM and symptoms (LI)Low resource setting, LM epidemiologyIf gastroscopy is performed for other reasonsTo be determinedLD/LNP epidemiology
  • LD, lactase deficiency; LI, lactose intolerance; LM, lactose malabsorption; LNP, lactase non-persistence; SIBO, small intestinal bacterial overgrowth.