Q&A: Evaluation Of Chronic Cough

The symptom of cough is one of the most common symptoms for which outpatient care is sought. In an outpatient pulmonary practice, evaluation and management of persistent cough can account for up to 40 percent of the practice volume. Acute cough exists for less than three weeks and is most commonly due to an acute respiratory tract infection. Cough that has been present longer than three weeks is either subacute (three to eight weeks) or chronic (more than eight weeks).

This article is for Medical Students & Professionals

This is a Question & Answer revision article designed for medical students and professionals preparing for the PLAB, MRCP or USMLE examinations. They are based on actual questions from these examinations. You may find the Cough article more useful, or one of our many articles on Diseases & Conditions, Medical Syndromes, Health & Wellness or Home Remedies.

In this article:
Diagnostic approach to chronic cough
MCQ: clinical scenario
MCQ: answer
MCQ: explanation

Diagnostic approach to chronic cough

The history often provides important initial clues in the patient with subacute or chronic cough. All patients should be questioned about cigarette smoking, the use of ACE inhibitors, and about the presence of an upper respiratory tract infection at the onset of the cough. A history of coexisting symptoms might suggest an underlying diagnosis (eg, asthma, postnasal drip, gastroesophageal reflux, chronic bronchitis, bronchiectasis). Somewhat surprisingly, one study found that the character and timing of the cough and the presence or absence of sputum production do not appear to aid in the differential diagnosis. In patients whose cough has lasted more than eight weeks, a chest radiograph should be considered as part of the initial evaluation, especially if upper airway cough syndrome, asthma, or gastroesophageal reflux are not considered clinically likely.

Upper airway cough syndrome, asthma, and gastroesophageal reflux, alone or in combination, are responsible for approximately 90 percent of cases of chronic cough. However, one study found that these disorders were responsible for 99.4 percent of patients who had the following characteristics:

• Nonsmoker
• No use of an ACE inhibitor
• Normal or near normal and stable plain chest radiograph

Methacholine challenge and esophageal pH monitoring are useful diagnostic studies in the evaluation of selected patients with chronic cough.

MCQ: clinical scenario

A 60yr old farmer presents with a chronic cough and progressive dyspnea for the last 6yrs. The chest x-ray revealed a reticulonodular infiltrate associated with honey-combing of the lung. Pulmonary function studies show a restrictive pattern with loss of lung volumes, impaired diffusion capacity, decreased compliance, and an exercise-induced hypoxemia. Serum studies demonstrate precipitating antibodies against extracts of mouldy hay.

The causative organism in this case is likely to be:

a) Aspergillus
b) Thermophillic actinomycetes
c) Pencillium casei
d) Bacillus subtillis
e) Bacillus anthracis

MCQ: answer

The correct answer is B

MCQ: explanation

The pulmonary function tests are suggestive of a restrictive lung disease. The chest X-ray consisting of reticulonodular infiltrates and honey combing of the lung also point towards a restrictive lung disease most likely interstitial pneumonitis. The presence of precipitating antibodies against extracts of mouldy hay and the man's occupation clinches the diagnosis as that of a Farmer's Lung.

Farmer's lung is a rare kind of occupational disease seen in farmers due to exposure to dusts generated from harvested, humid warm hay that permits the rapid proliferation of spores of thermophillic actinomycetes. It is a type of hypersensitivity pneumonitis in which interstitial lung involvement occurs. The disease has an insidious course over years associated with chronic cough and progressive dyspnea. End stage lung disease is characterized by a fibrotic lung with reticulonodular infiltrates and honey combing of the lung.

Aspergillus is responsible for a variety of occupational and other interstitial lung diseases with prolonged symptoms but it is not the causative agent of farmer's lung. Pencillium casei is responsible for cheese washer's lung. Bacillus subtillis is responsible for detergent worker's disease. Bacillus anthracis is responsible for pulmonary anthrax which is a very acute disease resulting in death within days if not treated. It also causes parenchymal pneumonia rather than interstitial lung involvement.

Reference(s)
1). UpToDate: Evaluation of subacute and chronic cough in adults. Available online: https://www.uptodate.com/contents/evaluation-of-subacute-and-chronic-cough-in-adults