Overview of Breath Testing in Clinical Practice in North America

Bacterial overgrowth and lactose intolerance: how to best assess

PURPOSE OF REVIEW

To provide an up-to-date review on the clinical assessment of two important gastrointestinal problems with overlapping symptomatology but diverse cause and testing methods. Small intestinal bacterial overgrowth (SIBO) is characterized by the presence of excess bacteria in the small intestine associated with bloating, distention, gas, and diarrhea. Lactose intolerance is caused by lactase enzyme deficiency in the small bowel mucosa leading to lactose malabsorption and symptoms of bloating, gas, and diarrhea.

RECENT FINDINGS

SIBO is assessed by hydrogen/methane breath test using glucose as a substrate and/or small bowel aspirate and culture but these tests have shortcomings. Consequently, several new diagnostic techniques, including novel capsule technologies and other approaches are being evaluated. Lactose intolerance can be assessed by hydrogen/methane breath test using lactose as a substrate, or small bowel mucosal lactase assay, genetic testing and lactose tolerance test, although the efficacy and practicality of these diagnostic modalities are not equal.

SUMMARY

In clinical practice, gas, bloating, distention, pain, and diarrhea are common gastrointestinal symptoms that often remain unexplained when routine gastrointestinal endoscopy, imaging, and stool tests are negative. These patients should be evaluated for SIBO and/or food intolerances including lactose intolerance.

Changes in Glucose Breath Test in Cystic Fibrosis Patients Treated With 1 Month of Lumacaftor/Ivacaftor

BACKGROUND

Alteration of the airway microbiota is a hallmark of cystic fibrosis (CF) pulmonary disease. Dysfunction of cystic fibrosis transmembrane regulator (CFTR) in the intestine also promotes changes in local microbiota such as small intestinal bacterial overgrowth (SIBO), which is common in CF. We evaluated whether therapy with the CFTR modulator combination lumacaftor/ivacaftor (luma/iva) has a beneficial impact on SIBO as measured by breath testing (BT).

METHODS

A multicenter longitudinal study of CFTR-dependent disease profiling (NCT02477319) included a prospective evaluation for SIBO by BT. Tidal breath samples were collected after fasting and 15, 30, 45, 60, 90, and 120 minutes after ingestion of glucose, before and 1 month after subjects initiated luma + iva.

RESULTS

Forty-two subjects enrolled in the sub-study (mean age = 23.3 years; 51% female; 9.5% Latinx); 38 completed a hydrogen BT at both time points, of which 73.7% had a positive BT before luma/iva (baseline) and 65.8% had a positive test after luma/iva ( P = 0.44); shifts from negative to positive were also seen. Use of azithromycin (63.1%) and inhaled antibiotics (60.5%) were not associated with positive BT. Acid-blocking medications were taken by 73% of those with a negative BT at baseline and by 35% with a positive baseline BT ( P = 0.04).

CONCLUSION

We found a high rate of positive hydrogen breath tests in individuals with CF, confirming that SIBO is common. One month of luma/iva did not significantly change the proportion of those with positive breath hydrogen measurements.

Breath Metabolites to Diagnose Infection

BACKGROUND

Starkly highlighted by the current COVID-19 pandemic, infectious diseases continue to have an outsized impact on human health worldwide. Diagnostic testing for infection can be challenging due to resource limitations, time constraints, or shortcomings in the accuracy of existing diagnostics. Rapid, simple diagnostics are highly desirable. There is increasing interest in the development of diagnostics that use exhaled breath analysis as a convenient and safe diagnostic method, as breath sampling is noninvasive, secure, and easy to perform. Volatile organic compounds (VOCs) present in exhaled breath reflect the fingerprint of the underlying metabolic and biophysical processes during disease.

CONTENT

In this review, we overview the major biomarkers present in exhaled breath in infectious diseases. We outline the promising recent advances in breath-based diagnosis of respiratory infections, including those caused by influenza virus, SARS-CoV-2, Mycobacterium tuberculosis, Pseudomonas aeruginosa, and Aspergillus fumigatus. In addition, we review the current landscape of diagnosis of 2 other globally important infections: Helicobacter pylori gastrointestinal infection and malaria.

SUMMARY

Characteristic and reproducible breath VOCs are associated with several infectious diseases, suggesting breath analysis as a promising strategy for diagnostic development. Ongoing challenges include poor standardization of breath collection and analysis and lack of validation studies. Further research is required to expand the applicability of breath analysis to clinical settings.