Characteristics of different asthma phenotypes associated with cough: a prospective, multicenter survey in China.

Background: Asthma is a heterogeneous disease with variable symptoms, which presents with cough either as the sole or predominant symptom with or without wheezing. We compared the clinical and pathophysiological characteristics of cough predominant asthma (CPA), cough variant asthma (CVA) and classic asthma (CA) in order to determine any differential phenotypic traits.

Methods: In 20 clinics across China, a total of 2088 patients were finally recruited, including 327 CVA, 1041 CPA and 720 CA patients. We recorded cough and wheezing visual analogue scale, Leicester cough questionnaire (LCQ) and asthma control test scores. Fractional exhaled nitric oxide (FeNO), induced sputum cell counts, and capsaicin cough challenge were also measured and compared.

Results: CPA patients more frequently presented with cough as the initial symptom, and laryngeal symptoms (p < 0.001), had less symptoms related with rhinitis/sinusitis and gastroesophageal reflux (p < 0.05) than CA patients. Comorbidities including rhinitis and gastroesophageal reflux were similar, while the proportion of COPD and bronchiectasis was higher in CA patients. There were no differences in FeNO levels, sputum eosinophil and neutrophil counts, FEV1 (%pred) decreased from CVA to CPA to CA patients (p < 0.001). Cough sensitivity was higher in CVA and CPA compared to CA (p < 0.001), and was positively correlated with LCQ scores.

Conclusions: CVA, CPA and CA can be distinguished by the presence of laryngeal symptoms, cough sensitivity and airflow obstruction. Asthma-associated chronic cough was not associated with airway inflammation or comorbidities in our cohort. Trial registration The Chinese Clinical Trial Registration Center, ChiCTR-POC-17011646, 13 June 2017.