Can clinical characteristics differentiate patients with unexplained chronic cough from patients with asthma and COPD?

Background:

Chronic cough is reported in up to 20% of the adult population and often persists despite medical treatment with currently available therapies. Many clinical conditions, including asthma and chronic obstructive pulmonary disease (COPD), must be excluded before making a Unexplained chronic cough diagnosis.

Methods:

The primary objective was to use a large hospital dataset to compare clinical features of patients with a primary diagnosis of UCC with those with asthma or COPD without a primary diagnosis of UCC to help clinicians differentiate between these conditions more readily. Data were collected for all hospitalization and outpatient medical encounters for each patient between November 2013 and December 2018. Information included demographics, encounter dates, medications prescribed at every encounter for chronic cough, lung function testing, and hematologic parameters. Asthma and COPD were combined into one group to ensure there was no overlap with UCC and due to limitations of International Classification of Diseases coding to confirm an asthma(A)/COPD diagnosis.

Results:

Female gender represented 70% of encounters for UCC versus 61.8% for asthma/COPD (p < 0.0001); the mean age was 56.9 years for UCC versus 50.1 years for A/COPD (p < 0.0001). The number of patients on cough medications and the cough medication frequency were significantly higher in the UCC versus A/COPD group (p < 0.0001). UCC versus A/COPD patients had a total of eight versus three cough-related encounters over the study duration (i.e., 5 years) (<0.0001). The average interval between successive encounters was less for UCC (114 days) versus the A/COPD (288 days) group. Gender-adjusted Forced expiratory volume in the first second of exhalation/Forced vital capacity (FEV₁/FVC) ratios, residual volume%, and Diffusion capacity for carbon monoxide (DLCO%) were significantly higher in UCC versus A/COPD, whereas the response to bronchodilators of FEV₁, FVC and residual volumes were significantly greater in A/COPD patients.

Conclusions:

Clinical characteristics differentiating UCC from A/COPD could accelerate recognition of UCC diagnosis especially in the subspecialty setting where patients with these disorders are referred.