From the Guidelines
The lactose hydrogen breath test is the most widely used and probably superior method for diagnosing lactose intolerance, with a sensitivity and specificity similar to the mucosal lactase assay 1. The test involves ingesting 25–50 g lactose dissolved in 200–500 ml water after an overnight fast, and then collecting end expiratory breath samples at 15–30 minute intervals for three hours.
- A rise of hydrogen concentration from basal levels by more than 20 parts per million is compatible with a positive diagnosis of lactose intolerance.
- However, due to a false negative rate of up to 25%, a negative result does not exclude the diagnosis, and hence a trial of a lactose-free diet should be considered if the diagnosis is still suspected 1. Key considerations for the test include:
- The patient should fast overnight before the test
- The patient should ingest 25–50 g lactose dissolved in 200–500 ml water
- Breath samples should be collected at 15–30 minute intervals for three hours
- A significant increase in breath hydrogen levels indicates lactose malabsorption, which is a sign of lactose intolerance. It is essential to note that the lactose hydrogen breath test is relatively easy to perform, non-invasive, and does not require complex equipment, making it a practical diagnostic tool for lactose intolerance 1.
From the Research
Lactose Hydrogen Breath Test
- The lactose hydrogen breath test is currently the gold standard in diagnosing lactose intolerance 2.
- The test measures the amount of hydrogen in the breath, which is produced when undigested lactose is fermented by bacteria in the colon.
- A positive result is typically defined as a breath hydrogen concentration of 20 ppm or higher above baseline 2.
Sensitivity and Specificity
- The sensitivity of individual symptoms for lactose intolerance ranges from 39% (diarrhea) to 70% (bloating), while specificity ranges from 69% (bloating) to 90% (diarrhea) 2.
- A study found that shortening the hydrogen breath test to 3 hours did not significantly affect its sensitivity and specificity for diagnosing lactose malabsorption 3.
- Another study found that a three-sample test (0,120, and 180 minutes) had a false-negative rate of 5.9%, while a two-sample test (0 and 120 minutes) had a false-negative rate of 33.4% 4.
Diagnostic Accuracy
- A four-sample lactose hydrogen breath test (4SLHBT) has been validated as a diagnostic tool for lactose malabsorption in irritable bowel syndrome patients with diarrhea, with excellent diagnostic concordance with standard LHBT (97%-100%) 5.
- The use of lactase supplements has been shown to reduce clinical symptoms and hydrogen breath excretion in patients with lactose intolerance 6.
Test Duration and Sampling
- The duration of the hydrogen breath test can influence its sensitivity, with shorter tests (1-2 hours) having lower sensitivity than longer tests (3-4 hours) 3, 4.
- The number of breath samples taken during the test can also affect its accuracy, with three-sample tests having higher sensitivity than two-sample tests 4.