MCQs on Paediatric Respiratory Disorders

Written by Dr. Emily Chang (MBBS, FRACP) – Paediatrician

Question 1

A 5-month-old previously healthy infant is brought to the Emergency Department in winter with a 2-day history of cough, nasal congestion, and poor feeding. Today, the parents noted increased work of breathing. On examination, the infant is tachypnoeic with nasal flaring, subcostal retractions, and oxygen saturation of 91% in room air. Auscultation reveals widespread wheeze and crackles. There is no history of fever, vomiting, or aspiration.

What is the most appropriate management at this stage?

A) Start oral antibiotics and discharge home
B) Initiate nebulised salbutamol and observe for response
C) Admit for supportive care including oxygen and hydration
D) Order a chest X-ray to rule out pneumonia
E) Start corticosteroids to reduce airway inflammation

Correct Answer: C) Admit for supportive care including oxygen and hydration

Explanation:

This child presents with classic symptoms of bronchiolitis, a common viral lower respiratory tract infection in infants, typically caused by respiratory syncytial virus (RSV).

Key features include cough, tachypnoea, increased work of breathing, wheeze and crackles, and hypoxia. Management is supportive – focusing on oxygen supplementation if saturations are <92%, and hydration (oral or nasogastric/IV fluids as needed).

Antibiotics (A) are not indicated unless there’s evidence of bacterial infection.
Nebulised salbutamol (B) and corticosteroids (E) are not routinely effective in bronchiolitis.
Chest X-ray (D) is not routinely required unless the diagnosis is uncertain or severe deterioration occurs.

Hospital admission is warranted due to oxygen desaturation and respiratory distress.

Question 2

A 4-year-old boy is brought to the clinic with a chronic history of persistent cough, frequent bulky foul-smelling stools, and poor weight gain despite a good appetite. He has had multiple chest infections requiring antibiotics over the past year. On examination, he appears thin with nasal polyps and digital clubbing. His respiratory rate is mildly elevated, and scattered crepitations are heard in the lungs.

What is the most appropriate initial investigation to confirm the diagnosis?

A) Chest X-ray
B) Stool culture
C) Sweat chloride test
D) Genetic testing for CFTR mutation
E) Full blood count

Correct Answer: C) Sweat chloride test

Explanation:

The clinical presentation — chronic respiratory symptoms, steatorrhea, failure to thrive, digital clubbing, and recurrent chest infections — is highly suggestive of cystic fibrosis (CF).

The sweat chloride test is the gold standard initial diagnostic test for CF. A chloride concentration ≥60 mmol/L on two separate occasions is considered diagnostic in the appropriate clinical context.

Chest X-ray (A) may show hyperinflation or bronchiectasis but is not diagnostic.
Stool culture (B) may help identify infections but not diagnose CF.
Genetic testing (D) is confirmatory and used to identify specific CFTR mutations but is usually done after or alongside the sweat test.
Full blood count (E) may show infection but is nonspecific.

Key diagnostic clue: A combination of respiratory symptoms and pancreatic insufficiency in a child should raise suspicion of CF.

Question 3

A 4-year-old boy named Lucas is brought to the clinic with a chronic history of persistent cough, frequent bulky foul-smelling stools, and poor weight gain despite a good appetite. His parents mention that he has had multiple chest infections over the past year, often requiring antibiotics. On examination, he appears thin with visible nasal polyps and digital clubbing. His respiratory rate is mildly elevated, and scattered crepitations are noted bilaterally on chest auscultation.

What is the most appropriate initial investigation to confirm the diagnosis?

A) Chest X-ray
B) Stool culture
C) Sweat chloride test
D) Genetic testing for CFTR mutation
E) Full blood count

Correct Answer: C) Sweat chloride test

Explanation:

The clinical features in Lucas — including chronic productive cough, recurrent respiratory infections, bulky malodorous stools (steatorrhea), failure to thrive, nasal polyps, and digital clubbing — are classic for cystic fibrosis (CF). This autosomal recessive disorder results from mutations in the CFTR gene, affecting chloride transport across epithelial cells and leading to thick mucus production in the lungs, pancreas, and gastrointestinal tract.

The sweat chloride test is the most appropriate initial diagnostic investigation. It is a non-invasive test that measures the concentration of chloride in sweat. In children with CF, chloride levels are typically ≥60 mmol/L on two separate occasions, which is diagnostic in the correct clinical context.

While a chest X-ray may reveal hyperinflation, peribronchial thickening, or bronchiectasis, it is not diagnostic. A stool culture is not useful for diagnosing CF but may identify secondary infections. Genetic testing for CFTR mutations is important, especially for carrier screening or confirming rare mutations, but it is usually done after a positive sweat test or if the sweat test is equivocal. A full blood count is nonspecific and may only show inflammation or infection.

Early diagnosis and initiation of multidisciplinary care significantly improves the prognosis in CF. Hence, prompt identification through the sweat chloride test is essential in children with suggestive symptoms.

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15. Paediatrics Module

15.1 Neonatology

15.2 Growth and Development

15.3 Paediatric Neurology

15.4 Paediatric Cardiology

15.5 Paediatric Respiratory

15.6 Paediatric Gastroenterology

15.7 Paediatric Nephrology

15.8 Paediatric Infections

15.9 Other Paediatric Disorders