Diagnosis of Cystic Fibrosis
Diagnosis of cystic fibrosis involves a combination of newborn screening, genetic testing, and clinical evaluation. Early detection is crucial because it allows for timely treatment, which can slow disease progression and improve long-term outcomes. In many developed countries, healthcare providers diagnose cystic fibrosis shortly after birth through routine screening programmes.
Newborn Screening
In countries with universal newborn screening:
Healthcare providers perform a heel-prick blood test within the first few days of life
The test measures immunoreactive trypsinogen (IRT), a protein that elevated levels may indicate in babies with cystic fibrosis
If IRT levels are high, healthcare providers initiate further testing, including DNA analysis to detect common CFTR mutations
Early screening allows for treatment to begin before serious complications arise, especially nutritional deficiencies and infections.
Sweat Test
The gold standard for diagnosing cystic fibrosis is the sweat chloride test:
A painless method where sweat is stimulated from the skin and collected
Measures the chloride level in the sweat—elevated levels are indicative of CF
This test is typically performed if the newborn screen or genetic test raises suspicion
A chloride concentration above 60 mmol/L is generally diagnostic for cystic fibrosis, while values between 30–59 mmol/L may require further investigation.
Genetic Testing | Diagnosis of Cystic Fibrosis
Confirms the presence of mutations in the CFTR gene
Can identify carrier status in parents and siblings
Used to confirm diagnosis in patients with borderline sweat test results
Genetic testing is particularly useful when dealing with atypical cases or adult-onset symptoms.
Other Diagnostic Evaluations
Once cystic fibrosis is confirmed, additional assessments help determine the extent of organ involvement:
Chest X-rays or CT scans to evaluate lung structure
Lung function tests (spirometry) to assess airway obstruction
Stool tests to measure digestive enzyme output
Blood tests to evaluate nutrition and liver function
Prenatal Diagnosis
For couples with a known family history:
Chorionic villus sampling (CVS) or amniocentesis can detect CFTR mutations in the fetus
Genetic counselling is strongly recommended for at-risk families
In summary, diagnosis of cystic fibrosis relies on early screening and confirmatory testing. Advances in genetic analysis and newborn screening have enabled earlier diagnosis, helping to prevent complications and begin intervention from infancy.
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