Characteristics of idiopathic pulmonary fibrosis -associated cough. a case-control study

Most patients with idiopathic pulmonary fibrosis (IPF) complain of cough. IPF-associated cough is widely characterized as dry or non-productive. The aim of this study was to compare chronic cough in early stage IPF patients to cough in subjects with chronic cough from a community-based sample and, especially, to investigate whether cough in IPF is less productive than chronic cough in a community-based sample.

The IPF cough population consisted of 46 biopsy-confirmed patients who complained of chronic cough. Control population consisted of subjects with chronic cough, gathered by a community-based email survey sent to public service employees and the Finnish Pensioners' Federation. A case-control setting was applied by having four age, gender, and smoking-status matched subjects from the community sample for each IPF cough patient. A cough specific quality of life questionnaire (Leicester Cough Questionnaire (LCQ)) was filled in by all subjects. The LCQ questionnaire contains 19 questions, each question is scored from 1 to 7 and total score from 3 to 21 with a smaller value indicating more severe impairment.

The sputum production frequency, as assessed by LCQ question 2, was 5.0 (3.0-6.0) in the IPF chronic cough population and 5.0 (3.0-6.0) in the community-based chronic cough population (median and interquartile range p= 0.72). The LCQ total score was 14.8 (11.5-18.1) in the IPF chronic cough population and 15.4 (13.0-17.5) in the community-based chronic cough population (p=0.76). The domain impact scores were physical, 4.9 (3.9-6.1) vs. 5.1 (4.5-5.6) (p=0.80); psychological, 4.6 (3.7-5.9) vs. 4.7 (3.9-5.7) (p=0.90); and social, 5.5 (3.7-6.5) vs. 5.5 (4.5-6.3) (p=0.84), respectively. Furthermore, cough response to paint or fumes, cough disturbing sleep, and cough frequency per day did not differ between the groups.

Cough in early stage IPF patients was not distinguishable from chronic cough in the community-based population by LCQ. Especially, there was no difference in the self-reported frequency of cough-associated sputum production.