Breath testing for asthma and COPD.

Background and rationale:

Diagnosing and monitoring of asthma and COPD is based on clinical presentation and repeated measurement of lung function. However, these tests are time-consuming and not widely applicable. Furthermore, differential diagnosis, (sub)phenotyping and monitoring of obstructive lung diseases remain difficult, which hinders clinical management, especially in primary care.

Simple and fast diagnostic methods in asthma and COPD are therefore needed, and improving accuracy and cost-effectiveness of diagnosing and monitoring can contribute to improved management of the diseases.
Using exhaled air as the source for measuring biomarkers is attractive because it is noninvasive and allows repeated sampling. Heterogeneity in asthma and COPD is also likely to be reflected in the composition of the exhaled air, which is known to contain thousands of volatile organic compounds (VOCs) that are derived from various metabolic pathways taking place in the lung and elsewhere in the body. These VOCs, alone or in combination, can potentially be used as biomarkers for the obstructive airways diseases in general and more specifically, for its several subclasses.
Electronic nose (eNose) technology is based on an array of sensors reacting to the many volatile organic compounds (VOC’s) in breath, combined with pattern recognition algorithms. Recently, Fens et al demonstrated that an electronic nose was able to distinguish the breathprints from patients with asthma, COPD and smoking and non-smoking healthy controls (AJRCCM 2009). In an external validation study, asthma and COPD could be diagnosed with high sensitivity and specificity in patients with ‘classic’ disease and in patients with persistent airways obstruction with either COPD or asthma [Fens et al, submitted].

The current study aims to estimate the diagnostic accuracy for asthma and COPD of exhaled breath measurement using the electronic nose in patients with an intention to diagnose, following the STARD criteria.

We postulate that exhaled breath sampling by an electronic nose can adequately identify asthma or COPD in breathprints from patients with an intention to diagnose.

Visits to outpatient and pulmonary function clinics as scheduled for routine diagnostic workup. Measurement of primary outcome (electronic nose) will be performed once, preferably at the first visit.

Electronic nose: The Cyranose 320 (Smith Detections, Pasadena, Ca, USA), a handheld portable chemical vapor analyzer, containing a nanocomposite sensor array with 32 polymer sensors. Patients will breathe normally through a mouthpiece, connected to a three-way non-re-breathing valve and an inspiratory VOC-filter (A2, North Safety, NL) for 5 minutes. After a single deep inspiration the patient exhales a vital capacity volume into a Tedlar bag connected to the expiratory port. Within 30 minutes the electronic nose will be connected to the Tedlar bag, followed by 1 minute sampling of the exhaled air.



Diagnostic work-up for asthma or COPD.

According to usual care.

At least pre-bronchodilator spirometry and symptoms.



Skin prick test/RAST: Allergy testing.

Spirometry: Pre- and postbronchodilator spirometry according to ERS/ATS recommendations.

Exhaled NO: Using the Niox Aerocrine or Niox Mino according to the ATS recommendations (ATS NO).

Bronchial responsiveness by histamine or methacholine challenge according to ERS/ATS recommendations.

Symptoms: Questionnaires for assessing symptoms of asthma and COPD and for co-morbidity will be used.