Breath sampling and analysis for biomonitoring and early disease diagnosis
Tuesday, 10 December 2019 at 3:29:PM
Exhaled breath is a good indicator of compounds contained
within the bloodstream and directly reflects actual disease activity. Breath
analysis by TD–GC–MS holds the promise of non-invasive, early detection for
life-threatening conditions such as lung cancer, breast cancer, liver disease
and inflammatory bowel disease, all of which have been found to influence the
profile of volatile organic compounds (VOCs) in the breath.
Outputs of breath analysis
reveal a complex and diverse composition. The value lies in finding those
compounds (biomarkers) whose concentrations consistently show differences between
the breath of patients and that of healthy controls (see Figure 1).
Figure 1. VOC profiles from the breath of a patient and a
healthy control, as obtained by TD–GC–MS. Compounds 1-4 are consistently up /
downregulated in the breath of cancer patients. (Markar, S. R., Brodie, B.,
Chin, S.-T., Romano, A., Spalding, D., & Hanna, G. B. (2018). Profile of
exhaled-breath volatile organic compounds to diagnose pancreatic cancer.
British Journal of Surgery, 105(11), 1493–1500. https://doi.org/10.1002/bjs.10909).
breath research has been mostly done in academic research labs, but in recent
years several companies have emerged onto the commercial breath research scene.
One of the largest players in this field is Cambridge-based Owlstone Medical
with their Breath Biopsy® product in use in more than 100 clinics worldwide.
This development of this field of study offers the intriguing possibility
of breath analysis making the leap from research to clinical practice. This
would open up the screening of large populations, improving patient survival
and reducing costs for health services.
successful transition from benchtop to bedside requires a valid basis for
reproducible and standardized breath VOC collection. The resolution of logistical
issues such as the collection of breath from a high number of patients across multiple
remote locations is one of the challenges.
to breath sampling
With growing interest in breath monitoring for disease
diagnosis researchers have a choice of products and methodologies for sampling.
Ideally a breath sampling device should be low cost, portable and easy to use.
Storage and transportation of the samples for analysis must also be simple,
secure and convenient – thermal desorption tubes provide this. Available options vary in complexity, cost
and ability to select specific fractions of exhaled breath, since the
composition of exhaled air will progressively change when it moves throughout
the airways, from the alveoli to the mouth.
Sampling approaches include:
- Disposable bags made of various materials (e.g. Nalophan, Tedlar, inertised aluminium) can be used to collect a defined volume of breath from a few hundred milliliters to a few liters. However, samples collected in this way have limited stability (from a few hours to a few days, depending on the compound of interest) and bags offer poor transportability. Alternatively, breath samples can be immediately transferred from bags to TD tubes using a portable pumping device (e.g. ACTI-VOC or Easy-VOC). When collecting breath using a bag it should be noted that all fractions of breath including mouth air are sampled without discrimination.
- Markes’ BioVOC-2 breath sampler, a recent introduction to the market – a lightweight and easy-to-use device for non-invasive biological exposure monitoring of VOCs. Using a design pioneered by the UK Health & Safety Executive over two decades ago, BioVOC-2 captures expiratory breath for immediate transfer to sorbent TD tubes. These are then typically analysed via TD–GC–MS. In contrast to use of disposable bags, BioVOC-2 captures just the last 129 mL of expired air, thus reducing contamination with VOCs from the mouth. Whilst the sampler’s predecessor, Bio-VOC has been successfully used for occupational health monitoring and exposure of the public to VOCs, its main area of application is clinical research. Scientists from research groups worldwide have used Bio-VOC in their research and this type of breath sampling is increasingly seen as suitable for large-scale screening of susceptible populations.
- Breath sampling devices of varying degrees of sophistication have been developed by research groups worldwide. The ReCIVA® from Owlstone Medical represents a commercial solution which allows simultaneous, direct transfer of a fixed volume of exhaled breath onto four TD tubes using a disposable face mask and built-in pumps. Pressure and CO2 sensors allow specific fractions of exhaled breath to be selected ensuring reliable, reproducible collection of VOCs. Subjects breathe a controlled supply of air, and samples of their exhaled breath are captured and stabilised on Breath Biopsy Cartridges, which can then be shipped for analysis with Owlstone Medical’s Breath Biopsy analytical platform to determine their VOC profile. Advanced data analytics techniques can then be applied in order to pinpoint the VOCs of interest. Owlstone is currently running a number of clinical studies including the world's largest breath based clinical trial.
Breath and beyond
The prevalence of
studies dealing with VOC analysis within different types of biological matrices
has been increasing in recent years. The most represented biological matrix is
breath, but bodily fluids (e.g. blood or urine) or tissues are also studied alongside
breath to confirm the identity of biomarkers and establish their kinetics of
distribution throughout the body. The increase in scientific production in the
field of VOC analysis is also accompanied by an increasing interest from the
clinical community, as witnessed by the recent rise in the number of clinical
trials involving breath analysis.
Figure 2. Clinical trials involving breath analysis, based on
start date (source: ClinicalTrials.org).
and Breath Biopsy® are a registered trademarks of Owlstone Medical
Nick van Noorden
Nick van Noorden joined Markes
International in 2018 as Marketing Manager – Supplies. He started his career in scientific
publishing and has a background in marketing communications & strategy for organisations
in the business, consumer and not-for-profit sectors.