Pulmonology focuses on diagnosing and treating lung and airway conditions such as asthma, COPD, and pneumonia, as well as overall respiratory health.

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The Newborn Screening Paradigm

The diagnostic landscape of cystic fibrosis has been fundamentally altered by the implementation of universal newborn screening (NBS). In the United States, Europe, and many other regions, infants are screened shortly after birth. This proactive approach allows for the initiation of nutritional and respiratory therapies before clinical symptoms cause irreversible damage. The screening algorithm typically involves collecting a blood spot from the infant’s heel on a Guthrie card. The sample is analyzed for immunoreactive trypsinogen (IRT), a pancreatic enzyme precursor elevated in the blood of infants with pancreatic stress or obstruction. If the IRT level is elevated (in the top percentile), the sample undergoes secondary testing, usually DNA analysis for a panel of common CFTR mutations. A positive screen identifies infants at high risk but is not diagnostic; it requires confirmatory testing. At Liv Hospital, we guide families through this often anxiety-provoking process, ensuring rapid follow-up.

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The Sweat Chloride Test: The Gold Standard

Despite advances in genetics, the quantitative pilocarpine iontophoresis sweat test remains the diagnostic gold standard. It provides a functional assessment of CFTR activity.

  • Methodology: The test involves stimulating a localized area of skin (usually the forearm or thigh) to sweat using pilocarpine, a chemical, and a mild, painless electrical current. The sweat is then collected onto a gauze pad or into a microbore coil for about 30 minutes.
  • Diagnostic Criteria: The chloride concentration in the sweat is measured.
  • A chloride level≥60 mmol/L is diagnostic of cystic fibrosis.
  • Levels between 30 and 59 mmol/L are considered intermediate (CRMS/CFSPID) and require further evaluation.
  • Levels ≤29 mmol/L are normal.
  • Importance: This test is crucial because it measures the protein’s functional activity, confirming the diagnosis even in cases with rare genetic mutations not detected by standard screening panels.
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Molecular Genetic Testing

Genotyping is an essential component of the evaluation, not just for diagnosis but for treatment planning. Since CFTR modulators are mutation-specific, knowing the exact genotype is mandatory.

  • Mutation Panels: Initial testing usually involves screening a panel of the most common mutations (e.g., the 23-100 most frequent variants) relevant to the local population.
  • Complete Gene Sequencing: If a patient has a positive sweat test or clinical symptoms but only one or no mutations are identified on the panel, complete sequencing of the CFTR gene is performed.
  • Deletion/Duplication Analysis: This looks for large missing or repeated sections of the gene that sequencing might miss.
  • CFTR2 Database: Clinicians use the Clinical and Functional Translation of CFTR (CFTR2) database to interpret the clinical consequences of identified variants, distinguishing between disease-causing mutations and benign polymorphisms.

Physiological Evaluation: Pulmonary Function Testing

Once a diagnosis is established, monitoring lung function becomes routine care, typically starting at age 5 or 6, when children can reliably perform the maneuvers.

  • Spirometry: This measures the volume and speed of air exhaled. The key metric is FEV1 (Forced Expiratory Volume in 1 second). The FEV1 percent predicted tracks disease progression; a decline indicates worsening obstruction.
  • Lung Clearance Index (LCI): For younger children or those with mild disease where spirometry is normal, LCI is a more sensitive tool. It uses a tracer gas washout technique to measure ventilation inhomogeneity (uneven air distribution) caused by early small airway disease.
  • Infant Pulmonary Function Testing: Specialized centers can perform lung function testing in sedated infants to detect airflow limitation in the first months of life.

Microbiological Surveillance

Regular surveillance of airway microbiology is critical. At every clinic visit (typically quarterly), respiratory cultures are obtained via sputum expectoration or oropharyngeal swabs (in non-expectorating children).

  • Pathogen Identification: The lab looks for key CF pathogens: Staphylococcus aureus, Haemophilus influenzae, Pseudomonas aeruginosa, Burkholderia cepacia complex, Stenotrophomonas maltophilia, and Achromobacter.
  • Fungal and Mycobacterial Cultures: Annual screening for allergic bronchopulmonary aspergillosis (ABPA) and nontuberculous mycobacteria (NTM) is performed, as these require specific and prolonged treatments.
  • Sensitivity Testing: Determining the antibiotic susceptibility profile of these organisms guides the choice of drugs for eradication and exacerbation management.

Radiological Imaging

Imaging provides a structural assessment of disease progression.

  • Chest Radiography: Used for acute assessment during exacerbations to rule out pneumonia, pneumothorax, or large areas of atelectasis.
  • High-Resolution Computed Tomography (HRCT): The standard for detailed structural evaluation. It can detect early bronchiectasis, mucus plugging, and air trapping long before they are apparent on X-rays or spirometry. Protocolized low-dose CT scans are often performed every 2-3 years.
  • Abdominal Imaging: Ultrasound is used to screen for liver disease (cirrhosis, fatty liver) and portal hypertension.

Assessment of Pancreatic and Metabolic Status

  • Fecal Elastase: This test measures the level of elastase-1 in the stool. Levels <200 mcg/g indicate pancreatic insufficiency, necessitating enzyme replacement therapy.
  • Oral Glucose Tolerance Test (OGTT): Starting at age 10, an annual OGTT is performed to screen for Cystic Fibrosis-Related Diabetes (CFRD). HbA1c is not a sensitive screening tool for CFRD.
  • Vitamin Levels: Annual blood levels of fat-soluble vitamins (A, D, E, K) are checked to adjust supplementation dosages.

Bronchoscopy and Lavage

In cases where patients are unable to produce sputum but clinical decline is evident, or to guide treatment for persistent infections, a flexible bronchoscopy with bronchoalveolar lavage (BAL) may be performed. This involves washing a segment of the lung with saline and collecting the fluid for culture, providing a “deep” sample of the lower airway microbiology.

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Assoc. Prof. MD. Engin Aynacı Assoc. Prof. MD. Engin Aynacı Pulmonology Overview and Definition
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FREQUENTLY ASKED QUESTIONS

Can a baby fail the newborn screen and not have CF?

Yes, a positive newborn screen means the baby is at risk, but many babies with positive screens are only carriers or have false-positive results; the sweat test confirms the diagnosis.

Yes, the sweat test is the gold standard for all ages. However, diagnosing adults can sometimes be more complex if they have atypical symptoms or borderline sweat chloride levels.

A chest CT is much more sensitive than an X-ray; it can detect early damage, such as minor airway scarring or trapped mucus, that an X-ray misses, allowing for earlier treatment.

LCI is a sensitive breathing test that measures how evenly air flows through the lungs; it can detect early lung disease in children even when their standard spirometry results are expected.

Current guidelines recommend obtaining a respiratory culture at least 4 times a year (at every clinic visit) to monitor bacteria and treat new infections promptly.

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