Published Online: July 7, 2015
For clinicians in a typical outpatient setting, detecting airways disease is often difficult. In addition, differentiating asthma from other respiratory diseases like Chronic Obstructive Pulmonary Disease (COPD) can be difficult as both have somewhat similar clinical presentations. Most clinicians continue to rely upon patient history and examination before administering trials of therapy. Metabolomics is the study of metabolic pathways and biochemical molecules created in a living system. By measuring changes in metabolites, biochemical effects induced by a disease or its therapeutic intervention can be determined. Urine is an excellent biological fluid owing to its ease of collection in patients of all ages, low cell and protein content, and rich chemical composition.
The pathology of asthma is different from that seen in COPD, and the degree of inflammation and cellular damage varies with disease severity. It has been previously reported that metabolomic profiling of urine could differentiate asthma from healthy subjects. In a recent publication in The Journal of Allergy and Clinical Immunology, Adamko and colleagues hypothesize that the metabolic activity of adults with asthma would differ from those with COPD, and that this difference could be measured using metabolomic analysis of urine samples. Clinical and urine-based metabolomic data were collected from adults meeting criteria of asthma and COPD before and after a visit to the emergency room. We also recruited subjects with stable asthma or COPD in outpatient clinic. Metabolites were measured in urine using nuclear magnetic resonance (NMR). Partial least squares discriminant analysis (PLS-DA) was performed on the NMR data to create models of separation (86 metabolites were measured/urine sample). Some subjects’ metabolomic data were withheld from modeling to be run blindly to determine diagnostic accuracy.
PLS-DA analysis of the urine NMR data found unique differences in select metabolites between asthma and COPD subjects seen in the ED and even in follow-up after exacerbation. Using these select metabolomic profiles, the model could correctly diagnose blinded asthma and COPD subjects with >90% accuracy.
In this report, it is demonstrated for the first time that analysis of metabolites in urine has the ability to differentiate adults with asthma versus those with COPD, both in the ED at the time of exacerbation and in follow-up post exacerbation. We suggest that using this approach in larger cohorts of patients will lead to a novel approach to the way doctors could diagnose and monitor their patients with airways diseases.
The Journal of Allergy and Clinical Immunology (JACI) is an official scientific journal of the AAAAI, and is the most-cited journal in the field of allergy and clinical immunology.