22nd February 2024

Diagnosis

Cystic fibrosis is diagnosed from clinical history and a combination of the following:

• Family history of cystic fibrosis
• Sweat sodium concentration >60mmol/l
• Serum DNA analysis
• Absence of vas deferens and epididymis

Laboratory evidence 

Sweat testing remains the main diagnostic testing for confirmation of CF. DNA analysis can also be undertaken if there is an intermediate sweat test result. The test involves the collection of sweat after pilocarpine inotrophesis and the chemical determination of chloride concentration. 

Radiological evidence 

Patients with CF will commonly present with features of bronchiectasis on a chest x-ray and CT. Areas of consolidation, hyperinflated lung fields, lymph node enlargement and pneumothorax are features of CF which can be seen on CXR. Mucus plugging, bronchial dilatation and pulmonary arterial enlargement secondary to pulmonary hypertension are features which can be visualised on CT. 

References

• Stern RC. The diagnosis of cystic fibrosis. N Engl J Med 1997; 336:487
• Rosenstein BJ, Cutting GR. The diagnosis of cystic fibrosis: a consensus statement. Cystic Fibrosis Foundation Consensus Panel. J Pediatr 1998; 132:589.
• Farrell PM, White TB, Ren CL, et al. Diagnosis of Cystic Fibrosis: Consensus Guidelines from the Cystic Fibrosis Foundation. J Pediatr 2017; 181S:S4