From the Guidelines
The accuracy rate of SIBO breath tests is generally low, with sensitivity and specificity ranging from 20-93% and 30-100%, respectively, depending on the specific test used. The hydrogen breath test is most common, but its accuracy is limited by factors such as false negatives in patients with slow transit time or predominantly hydrogen sulfide-producing bacteria, and false positives with rapid intestinal transit or certain dietary factors 1.
According to a study published in Gut in 2018, the sensitivity and specificity of glucose breath testing were found to be less than 50% and less than 70%, respectively, compared to duodenal aspirate 1. Another study published in Clinical Gastroenterology and Hepatology in 2019 reported that the sensitivity and specificity of lactulose hydrogen breath testing ranged from 31 to 68% and 44 to 100%, respectively 1.
Some key points to consider when interpreting SIBO breath test results include:
- Test preparation significantly impacts accuracy, requiring patients to follow a specific low-fermentable diet for 24-48 hours before testing, avoid antibiotics for 2-4 weeks prior, and fast for 8-12 hours immediately before the test
- The effect of rapid small intestinal transit in patients with IBS has cast doubt upon some of the indices claimed to be diagnostic of SIBO, whether lactulose or glucose is used as the substrate 1
- Breath testing remains the most practical non-invasive diagnostic tool for SIBO in clinical practice, though results should be interpreted alongside clinical symptoms for best diagnostic accuracy 1.
Overall, while SIBO breath tests can be a useful diagnostic tool, their accuracy is limited, and results should be interpreted with caution and in the context of clinical symptoms. The most recent and highest quality study suggests that the accuracy of SIBO breath tests is generally low, and therefore, clinical judgment and correlation with symptoms are essential for accurate diagnosis 1.
From the Research
Accuracy Rate of SIBO Breath Test
The accuracy rate of the SIBO breath test can be evaluated based on several studies.
- The sensitivity, specificity, positive and negative predictive values, and diagnostic accuracy of glucose hydrogen breath test (GHBT) to diagnose SIBO were 44%, 80%, 62%, 67%, and 65%, respectively 2.
- The corresponding values for lactulose hydrogen breath test (LHBT) were 31%, 86%, 62%, 54%, and 55%, respectively 2.
- A study found that breath testing for SIBO can be maximized by careful patient selection, proper test preparation, and standardization of test performance and interpretation 3.
- The measurement of methane in addition to hydrogen can increase the sensitivity of breath testing for SIBO 3.
- A consensus meeting of experts developed guidelines for clinicians and research, including the use of glucose and lactulose breath tests to diagnose SIBO, with a rise in hydrogen of ≥20 ppm by 90 minutes considered positive 4.
- Another study found that the complete eradication rate of SIBO was 35.9% in the rifaximin group and 34.1% in the combined group with no significant differences 5.
Factors Affecting Accuracy
Several factors can affect the accuracy of the SIBO breath test, including:
- Patient selection and preparation 3
- Test methodology and interpretation 4, 3
- Use of different substrates, such as lactulose or glucose 4, 3
- Measurement of methane in addition to hydrogen 3
- Oro-cecal transit time (OCTT) 2
Diagnostic Criteria
The diagnostic criteria for SIBO using breath testing include: