Lactulose breath test

The Lactulose breath test is an indirect method of measuring bacteria in the digestive tract. It can indicate the approximate population, location, and some information about the type of bacteria. It is used to diagnose Small Intestine Bacteria Overgrowth (SIBO).

Theory
Bacteria in the digestive tract produce gasses as a byproduct of food metabolism. Aerobic bacteria produce hydrogen gas, whereas anaerobic bacteria produce methane gas.

Both hydrogen and methane gasses produced by intestinal bacteria can be detected on a person's breath. Since food travels gradually through the small intestine before reaching the large intestine, the change in gas levels over time can indicate the location and population of bacteria.

Diagnosis of SIBO via breath testing is controversial due to the species-dependent nature of breath tests and the lack of an agreed threshold for a positive test.

Procedure
The test is preceded by a 24 hour preparation period, which includes a limited diet and a period of fasting. Baseline gas levels are measured from the patients breath at the beginning of the test. In order to prevent results from being affected by food already in the digestive tract, the procedure continues only if the baseline gas levels are below a certain threshold.

A small amount of Lactulose solution is consumed by the patient. The patient's breath is sampled periodically over the course of a few hours, typically every 15 to 30 minutes. The gas levels from each sample are measured and recorded, then typically plotted a on a line graph. SIBO may be indicated if one or both of the following criteria are met: Test equipment may measure the concentration (in PPM) of hydrogen gas, methane gas, or both. Measuring the concentration of both gasses is ideal to ensure that both aerobic and anaerobic bacteria are detected. However, testing may be limited to measuring only hydrogen due to available equipment and/or cost considerations.
 * Gas level rises above a certain threshold within a certain timeframe. (The idea is that an early rise must be from bacteria in the small intestine, as food would not have reached the large intestine yet.)
 * Gas level plot shows a double peak. (The idea is that this indicates two clusters of bacteria - one in the small intestine, and one in the large intestine.)

Cost and availability
Testing may be done in-office or at home using portable, possibly even handheld, breath testing equipment. Alternatively, breath samples may be collected using a kit then shipped to a remote lab for analysis.
 * Gastro+ is a handheld hydrogen breath test machine which available for use through some medical providers
 * GastroCHECK is a desktop hydrogen and methane breath test machine which is available for use through some medical providers
 * Genova Diagnostics - Small Intestinal Bacterial Overgrowth test is a collection kit which is sent via FedEx courier to the company's lab for analysis. Kits are sold through clinics / doctors.
 * TrueHealthLabs.com sells SIBO test kits from Genova Diagnostics direct to patients, without requiring a prescription.
 * QuinTron sells equipment for breath testing in-office, and kits for in-home collection. Kits require a prescription.