Cough: A Comprehensive Guide for MCCQE1 Preparation

Introduction

Cough is one of the most common presenting complaints in primary care in Canada. For the MCCQE1, candidates must demonstrate the ability to differentiate between benign, self-limiting causes and serious underlying pathology. As a Medical Expert under the CanMEDS framework, you are expected to apply a structured approach to diagnosis and management, adhering to Canadian Thoracic Society (CTS) guidelines.

Classification of Cough

The most clinically useful classification for the MCCQE1 is based on duration. This temporal framework narrows the differential diagnosis significantly.

Clinical Evaluation

History Taking (Data Acquisition)

For the MCCQE1, efficient history taking is paramount. You must identify Red Flags early.

Key Questions to Ask:

• Onset and Duration: Acute vs. Chronic.
• Sputum: Colour, volume, presence of blood.
• Triggers: Cold air, exercise (Asthma), lying flat (GERD/Heart Failure), eating (Aspiration/GERD).
• Associated Symptoms: Nasal congestion (UACS), heartburn (GERD), wheeze (Asthma).
• Medications: specifically ACE Inhibitors (up to 15% of patients; can occur months after initiation).
• Social History: Smoking (pack-years), occupational exposures (asbestos, silica), travel history (TB endemic areas).

Physical Examination

Focus on the respiratory and cardiovascular systems, plus the upper airway.

Diagnostic Approach: The MCCQE1 Algorithm

Follow this step-by-step approach, aligned with Canadian Thoracic Society (CTS) guidelines for Chronic Cough.

Canadian Guidelines & Epidemiology

Canadian Thoracic Society (CTS) Guidelines

The CTS emphasizes a systematic approach. A key differentiator in Canadian guidelines is the management of Pertussis.

• Pertussis (Whooping Cough): Endemic in Canada with periodic outbreaks.
  • Suspect in adults with > 2 weeks of cough, especially if paroxysmal, associated with vomiting, or inspiratory whoop.
  • Public Health: It is a reportable disease in Canada.

Tuberculosis (TB) Screening

Canada has a low incidence of TB, but rates are higher in:

• Foreign-born individuals from endemic countries.
• Indigenous populations (First Nations, Inuit, Métis).
• Homeless populations.
• MCCQE1 Tip: Have a low threshold for ordering a CXR and sputum AFB in these demographics if presenting with chronic cough.

Environmental Exposures

Be aware of Canadian occupational hazards:

• Grain dust: Farmers lung.
• Mining: Silicosis (common in parts of Northern Ontario/Quebec).

Key Points to Remember for MCCQE1

• ACE Inhibitors: Cough is a class effect. Angiotensin Receptor Blockers (ARBs) do not cause cough and are a safe alternative.
• Cough Variant Asthma: Asthma where cough is the only symptom. Spirometry may be normal; Methacholine challenge is the gold standard for diagnosis.
• UACS: The most common cause of chronic cough in non-smokers. Look for “cobblestoning” on the posterior pharynx.
• Red Flags: Hemoptysis + Smoker + Age > 55 = High suspicion for Lung Cancer. CT Chest is often the next best step after CXR.
• Code Block for Abbreviations:

  UACS = Upper Airway Cough Syndrome
  GERD = Gastroesophageal Reflux Disease
  NAEB = Non-asthmatic Eosinophilic Bronchitis
  ACE-I = Angiotensin-Converting Enzyme Inhibitor
  CXR = Chest X-Ray
  PFT = Pulmonary Function Test

Sample Question

Clinical Scenario

A 42-year-old female presents to your family medicine clinic with a persistent dry cough for the past 3 months. She reports a sensation of “something dripping” down the back of her throat and frequent throat clearing. She is a non-smoker and takes no medications. She has no history of asthma or heartburn. Physical examination reveals a normal chest auscultation, but inspection of the oropharynx shows a cobblestone appearance of the posterior pharyngeal mucosa. A chest X-ray performed last week was normal.

Question

Which one of the following is the most appropriate initial management step for this patient?

• A. Prescribe a trial of a proton pump inhibitor (PPI).
• B. Order a Methacholine Challenge Test.
• C. Prescribe a first-generation antihistamine and decongestant.
• D. Order a CT scan of the chest.
• E. Prescribe a course of oral antibiotics.

Explanation

The correct answer is:

• C. Prescribe a first-generation antihistamine and decongestant.

Detailed Explanation: This patient presents with a chronic cough (> 8 weeks) with specific symptoms and signs pointing towards Upper Airway Cough Syndrome (UACS), formerly known as post-nasal drip. The key features are the sensation of dripping, throat clearing, and the cobblestone appearance of the oropharynx (lymphoid hyperplasia).

• Option C is correct: According to Canadian Thoracic Society guidelines, in a non-smoker with a normal CXR and clinical features suggestive of UACS, an empiric trial of therapy is the appropriate next step. First-generation antihistamines (e.g., chlorpheniramine) combined with a decongestant are often effective for non-allergic UACS. If allergic rhinitis is suspected, intranasal corticosteroids are preferred.
• Option A is incorrect: While GERD is a top cause of chronic cough, this patient has no symptoms of reflux (heartburn), and the physical findings point strongly to UACS.
• Option B is incorrect: This would be appropriate if Cough Variant Asthma was the primary suspicion (e.g., nocturnal cough, triggers like cold air), but UACS is more likely given the pharyngeal findings.
• Option D is incorrect: A CT chest is not indicated as the initial step for a patient with a normal CXR and a high probability of a benign “Big Three” cause.
• Option E is incorrect: Antibiotics are not indicated for chronic cough unless there is evidence of bacterial infection (e.g., sinusitis, pneumonia), which is not present here.

References

1. Canadian Thoracic Society (CTS). Guideline: Management of Cough in Adults and Children. Available at cts-sct.ca .
2. Medical Council of Canada. Objectives for the Qualifying Examination (MCCQE) Part I.
3. Irwin RS, et al. Diagnosis and Management of Cough Executive Summary: ACCP Evidence-Based Clinical Practice Guidelines. Chest.
4. UpToDate. Evaluation of subacute and chronic cough in adults. (Accessed for current best practices).