Cystic Fibrosis Diagnosis and Management

Clinical Presentation

The Centers for Disease Control and Prevention recommends that failure to thrive with steatorrhea, recurrent respiratory infections with chronic pulmonary symptoms, and salty-tasting skin are diagnostic of cystic fibrosis, with pancreatic insufficiency present at diagnosis in over 80% of patients 1, 2
The American Academy of Pediatrics notes that acute viral respiratory infections commonly develop into lower respiratory tract infections in CF infants, and chronic cough typically becomes evident around 10.5 months of age 1

The American College of Allergy, Asthma, and Immunology guideline notes that asthma can cause recurrent wheezing and cough in infants, but does not cause steatorrhea, failure to thrive, salty skin, or the degree of chronic pulmonary findings with purulent drainage seen in CF patients 3
The Centers for Disease Control and Prevention recommends excluding CF in the differential diagnosis of children with episodic wheezing and cough, especially when accompanied by failure to thrive or steatorrhea 1, 2

The Cystic Fibrosis Foundation recommends immediate referral to a specialized CF center to prevent irreversible complications, with management including pancreatic enzyme replacement therapy, aggressive pulmonary care, and fat-soluble vitamin supplementation 1, 2
The American Thoracic Society notes that aggressive pulmonary care can prevent chronic Pseudomonas aeruginosa infection, which leads to irreversible lung damage and significantly impacts survival 1

Many infants with CF in the US are now asymptomatic at diagnosis due to universal newborn screening, which has been implemented in multiple states, as recommended by the Centers for Disease Control and Prevention 4
High-fat diets with fat-soluble vitamin supplementation (A, D, E, K) are required to offset malabsorption, according to guidelines from the American Academy of Pediatrics 4

Pancreatic enzyme replacement therapy (PERT) must be initiated immediately for infants with exocrine pancreatic insufficiency, as recommended by the Cystic Fibrosis Foundation, although the exact citation is not provided, a similar recommendation is made by the European Cystic Fibrosis Society 4

Íleo meconial can be the initial presentation in some neonates, and the disease is associated with pulmonary obstructive disease and respiratory failure, which is the primary cause of death in >90% of patients 5
The Centers for Disease Control and Prevention recommends that the diagnosis of cystic fibrosis be established through the presence of ≥1 characteristic phenotype or history of cystic fibrosis in a sibling or positive newborn screening, along with laboratory evidence of CFTR abnormality 5

The diagnostic criteria for cystic fibrosis include elevated sweat chloride concentrations (≥60 mEq/L), identification of two CFTR mutations associated with cystic fibrosis, and demonstration of characteristic abnormalities in ionic transport across the nasal epithelium 6
The sweat test can be performed accurately in most infants at 2-3 weeks of age, but not all infants produce sufficient amounts of sweat for reliable testing 5, 6

Classic cystic fibrosis manifests in early childhood, associated with pulmonary disease and pancreatic insufficiency, whereas atypical or non-classic cystic fibrosis has milder phenotypic symptoms and is often diagnosed in adolescents or adults 5
The median age of diagnosis through newborn screening is 0.5 months, compared to 14.5 months for symptom-based diagnosis 5

The Cystic Fibrosis Foundation recommends chronic azithromycin for children ≥6 years without Pseudomonas aeruginosa to reduce exacerbations, and prophylactic anti-staphylococcal therapy has been shown to reduce hospitalizations in the second year of life 6, 7
Modulator therapies, such as ivacaftor and elexacaftor-tezacaftor-ivacaftor, have received regulatory approval and have been shown to improve lung function and reduce exacerbations in patients with specific CFTR mutations 6