From the Guidelines
The lactose hydrogen breath test is the most widely used and recommended method for diagnosing lactose intolerance, due to its ease of performance, non-invasive nature, and similar sensitivity and specificity to the mucosal lactase assay. This test involves ingesting 25–50 g lactose dissolved in 200–500 ml water after an overnight fast, and then taking end expiratory breath samples at 15–30 minute intervals for three hours to measure the rise in hydrogen concentration 1. A rise of hydrogen concentration from basal levels by more than 20 parts per million is compatible with a positive diagnosis of lactose intolerance. Some key points to consider when performing the lactose hydrogen breath test include:
- The patient should fast for a certain period before the test to ensure accurate results
- The test is relatively easy to perform, particularly if an electrochemical cell is used for analysis
- A negative result does not exclude the diagnosis, due to a false negative rate of up to 25%, and a trial of a lactose-free diet should be considered if the diagnosis is still suspected 1. Other methods for detecting lactase deficiency, such as assay of mucosal lactase, lactose tolerance tests, and stool acidity tests, may also be used, but the lactose hydrogen breath test is generally preferred due to its advantages.
From the Research
Lactose Intolerance Test Methods
- The hydrogen breath test (HBT) is considered the gold standard for diagnosing lactose malabsorption 2.
- The HBT can be shortened to 3 hours without loss of sensitivity and specificity when a high dose of lactose load is used 2.
- Genotyping for the diagnosis of adult-type hypolactasia can be used as a first step to diagnose lactose intolerance in a patient population with unexplained abdominal complaints 3.
Hydrogen Breath Test Variations
- The sensitivity of the HBT decreases from 95% for the 3-hour HBT to 37% for the 1-hour HBT with lactose, and from 80% for 3-hour HBT to 21% for 1-hour HBT with milk 2.
- A lower dose of lactose (12.5g) can be used for the HBT, and most patients with a positive HBT-25 normally absorb a lower dose of lactose 4.
- Methane (CH4) measurements may be of additional value for the diagnosis of lactose intolerance, as 5.7% of patients were negative for H2 and positive for CH4 5.
Comparison with Lactose Tolerance Test
- The lactose tolerance test (LTT) is an easy and efficient test for diagnosis of lactose malabsorption, and positive LTT is associated with a higher breath hydrogen score than negative LTT 6.
- There is a trend towards more frequent symptom development following lactose load in LTT positive but not in lactose HBT positive patients 6.