A 4-year-old child has recurrent respiratory infections, failure to thrive, and bulky foul-smelling stools since infancy. Chest X-ray shows hyperinflation and bronchiectatic changes. What is the best diagnostic test?
- A Sputum culture
- B Sweat chloride test ✓
- C Serum immunoglobulin levels
- D Tuberculin skin test
Correct answer: B. Sweat chloride test
Explanation
The triad of recurrent respiratory infections, failure to thrive, and steatorrhea strongly suggests cystic fibrosis. The sweat chloride test is the gold standard diagnostic test, with values above 60 mmol/L being diagnostic. Sputum culture identifies organisms but does not diagnose the underlying condition. Immunoglobulin levels would be normal in cystic fibrosis.
Reference: Nelson Textbook of Pediatrics, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.