Grading Severity of Productive Cough Based on Symptoms and Airflow Obstruction

ABSTRACT

The binary approach to the diagnosis of Chronic Bronchitis (CB) is a major barrier to the study of the disease. We investigated whether severity of productive cough can be graded using symptoms and presence of fixed airflow obstruction (FAO), and whether the severity correlates with health status, exposures injurious to the lung, biomarkers of inflammation, and measures of airway wall thickening. Findings from a cross-sectional sample of 1,422 participants from the Lovelace Smokers Cohort (LSC) were validated in 4,488 participants from the COPDGene cohort (COPDGene). Health status was based on the St. George's Respiratory Questionnaire, and Medical Outcomes Study 36-Item Short Form Health Survey. Circulating CC16 levels were quantified by ELISA (LSC), and airway wall thickening was measured using computed tomography (COPDGene). FAO was defined as postbronchodilator FEV₁/FVC <0.7. The presence and duration of productive cough and presence of FAO or wheeze were graded into Healthy Smokers, Productive Cough (PC), Chronic PC, PC with Signs of Airflow Obstruction, and Chronic PC with Signs of Airflow Obstruction. In both cohorts, higher grade of severity correlated with lower health status, greater frequency of injurious exposures, greater airway wall thickening, and lower circulating CC16 levels. Further, longitudinal follow-up suggested that disease resolution can occur at every grade of severity but is more common in groups of lower severity and least common once airway remodeling develops. Therefore, severity of productive cough can be graded based on symptoms and FAO and early intervention may benefit patients by changing the natural history of disease.

KEYWORDS:

• Chronic bronchitis
• severity stages
• symptom scores
• wheeze
• radiographic measures of airway remodeling

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Acknowledgments

We thank Dr. Clifford Qualls, University of New Mexico Health Sciences Center, for help with the interpretation of the multi-state Markov-like model analyses, and Ms. Suzanne C Lareau RN, MS, FAAN for the careful editing of the manuscript.

Author contributions

YT, AS, HP, and PM made substantial contributions to conception and design; HP, RVG, AS, PM, and YT made substantial contributions to acquisition of data or analysis and interpretation of data. RVG drafted the manuscript and all authors made substantial contributions to revising it critically for important intellectual content, and final approval of the version to be published. All authors agree to be accountable for all aspects of the work.

Sources of support

This work was supported from funding by the State of New Mexico (appropriation from the Tobacco Settlement Fund), and from the National Institutes of Health (RO1 ES015482 and RO1 HL068111 to YT).

Declaration of interest

The authors report no conflict of interest.

Supplemental data

Supplemental data for this article can be accessed at: https://doi.org/10.1080/15412555.2018.1458218.

Additional information

Funding

This work was supported by the State of New Mexico, Tobacco Appropriation Fund; NIH Clinical Center, RO1 ES015482, RO1 HL068111.