TABLE 1

Studies indicating an overlap phenotype that included both asthma and COPD patients in cluster analysis

SubjectsTotal identified clustersOverlap clusterOverlap cluster characteristicsFirst author [ref.]
27 asthma and 22 COPD patients45 (10.2)
  • Severe airflow obstruction

  • Greatest post-bronchodilator reversibility

  • ↑ Sputum eosinophil % and ↑ serum IgE compared with COPD cluster but lower than asthma cluster

Wardlaw [18]
175 participants: Wellington Respiratory Survey515 (8.6)
  • Severe airflow obstruction

  • Greatest post-bronchodilator reversibility and peak flow variability

  • ↑ Pack-years smoking history

  • ↑ Serum IgE and peripheral blood eosinophils and high prevalence of eczema and rhinitis

  • Chronic sputum production

  • ↑ Prevalence of macroscopic emphysema

Weatherall [19]
191 patients ≥60 years of age (predominantly male smokers) with obstructive airway diseases359 (30.9)
  • Intermediate airflow obstruction and emphysema compared with the other two clusters

  • Greatest post-bronchodilator reversibility

  • ↑ Serum IgE

Jo [20]
389 subjects with symptoms of wheeze and breathlessness in last 12 months534 (8.7)
  • Severe airflow obstruction

  • High post-bronchodilator reversibility and peak flow variability

  • FeNO

  • ↑ Serum IgE

  • High pack-years smoking history

  • ↑ Neutrophil count and ↓ eosinophil count in blood

Fingleton [21]
86 patients with severe asthma and 75 patients with moderate-to-severe COPD347 (27.4)
  • ↑ Neutrophil count and ↓ eosinophil count in sputum

  • ↑ Sputum IL-1β, IL-8, IL-10 and TNF-α

  • ↑ Sputum bacterial load in patients with COPD

Ghebre [22]
191 patients with doctor-diagnosed asthma or COPD458 (30.4)
  • ↑ Blood eosinophil count

  • Low pack-years smoking history

  • High percentage of positive sensitisation to aeroallergens

  • ↑ Post-bronchodilator reversibility compared with COPD clusters

  • Intermediate airflow obstruction compared with asthma and COPD clusters

Rootmensen [23]
152 patients with asthma and 50 patients with COPD450 (24.8)
  • High pack-years smoking history

  • Airflow obstruction intermediate to COPD and asthma clusters

  • High prevalence of atopy and ↑ serum IgE, ↑ peripheral blood eosinophils and ↑ FeNO

Hirai [24]
877 patients with asthma and 228 patients with COPD: French national Bronchial Obstruction and Asthma Cohort3386 (34.9)
  • Worse airflow obstruction than asthma cluster but better compared with COPD cluster

  • ↑ Post-bronchodilator reversibility

Bourdin [25]

Data are presented a n (%), unless otherwise stated. Ig: immunoglobulin; IL: interleukin; TNF-α: tumour necrosis factor-α; FeNO: fractional exhaled nitric oxide.