Table 1.
Summary of the Methodological Aspects of the Three Datasets
| Sample Type | Discovery Cohort, Headspace | EMBER Cohort, Exhaled Breath | U-BIOPRED Cohort, Exhaled Breath |
|---|---|---|---|
| No. of subject/samples | N = 36 | N = 65 (cohort with sputum eosinophils, 24/65) | N = 42 (cohort with sputum eosinophils, 22/42) |
| Asthma conditions GINA 2023 treatment step in the sputum cohorts |
Stable severe asthma GINA* 5 (anti-IL-5 ± mOCS): 14/36 GINA 5 (mOCS): 6/36 GINA 4-5 (ICS/LABA only): 16/36 |
Acute asthma exacerbation GINA 1: 2 GINA 2–3: 9 GINA 4–5 (none on mOCS): 13 Asthma biologic: 0 |
Stable severe asthma GINA 4–5: 8 (not on mOCS) GINA 5: 14 (all on mOCS) Asthma biologic: 0 |
| Asthma phenotype according to sputum eosinophils ⩾ 3% | Eosinophilic: 22/36 Noneosinophilic: 14/36 |
Eosinophilic: 9/25 Noneosinophilic: 16/25 |
Eosinophilic: 14/22 Noneosinophilic: 8/22 |
| Fraction of exhaled breath collected | Not applicable—headspace of native sputum eosinophils | Mixed expiratory breath | Mixed expiratory breath |
| Exhaled breath container | Dedicated headspace collection systems, reported in Ref. 17 | ReCIVA Breath Sampler, 1 L of breath sampled from the phase II/III slope of the CO2 sensor trace | 10 L Tedlar bag (SKC) |
| Preconcentration method | Carbograph 1TD and Tenax TA 60/40 (Markes International) | Carbograph 1TD and Tenax TA 60/40 (Markes International) | Tenax (Tenax GR SS 6 mm × 7 inch; Gerstel) |
| Sample storage | Into sorbent tubes, at 4°C for no longer than 15 d | Into sorbent tubes, at 4°C after dry purge, for no longer than 72 h | Up to 39 d on sorbent tubes at 4°C, breath samples were purged onto to sorbent tubes within 10 min of acquisition. |
| Analytical platform | TD-GC-MS | TD-GC × GC-FID-MS | TD-GC-MS |
| Data processing platform | AnalyzerPro (Spectral Works, v.5.7) | MassHunter GC-MS Acquisition B.07.04.2260 (Agilent Technologies Ltd) GC Image v.2.6 GC Project and Image Investigator (JSB Ltd) |
Masshunter Quantitative Analysis (Agilent Technologies) |
| Multivariate statistical method | Elastic net regression fitted using the cv.glmnet function from the glmnet package in R.3.6.1 (R Core Team, https://www.R-project.org). | Elastic net regression fitted using the cv.glmnet function from the glmnet package in R.3.6.1 (R Core Team, https://www.R-project.org). | Elastic net regression fitted using the cv.glmnet function from the glmnet package in R.3.6.1 (R Core Team, https://www.R-project.org). |
Definition of abbreviations: EMBER = East Midlands Breathomics Pathology Node; FID = flame ionization detector; GC-MS = gas chromatography–mass spectrometry; GINA = Global Initiative for Asthma; ICS = inhaled corticosteroids; LABA = long-acting β antagonist; mOCS = maintenance oral corticosteroids; TD = thermal desorption; U-BIOPRED = Unbiased Biomarkers in Prediction of Respiratory Disease Outcomes.
*
Global Initiative for Asthma 2023, treatment intensity step (17).