Diagnosis Methods for Cystic Fibrosis

Cystic fibrosis is diagnosed through a series of tests and evaluations to confirm the presence of this genetic disorder. Early diagnosis of cystic fibrosis is crucial as it enables timely intervention and care, ultimately improving the individual’s quality of life.

Diagnosis During Pregnancy

The earliest diagnosis of cystic fibrosis typically occurs during pregnancy and shortly after birth. Early detection is vital for cystic fibrosis patients, as it allows for the prompt initiation of treatment and care, ultimately enhancing their quality of life.

Prenatal Diagnosis During Pregnancy

During the pregnancy, if genetic tests for both parents come back positive for cystic fibrosis, additional tests may be needed to determine if the baby will be born with the condition. Prenatal diagnostic tests can determine if the fetus has cystic fibrosis or is merely a carrier of the gene. Two different methods can be used for this diagnostic test. Amniocentesis, which involves collecting a small amount of fluid surrounding the fetus, is typically performed between 15 and 20 weeks of pregnancy. Another method is chorionic villus sampling, which involves taking a small biopsy from the placenta using a special needle. This procedure is often done between 10-13 weeks of pregnancy.

Early Diagnosis Through Newborn Screening

In recent years, many countries have implemented newborn screening programs for early cystic fibrosis diagnosis. This program became crucial in identifying the condition early. In our country, this screening test has been applied to all newborns since 2015. The cystic fibrosis newborn screening test is a relatively inexpensive test that relies on the analysis of immunoreactive trypsinogen (IRT) levels in a blood sample obtained from the baby’s heel. Elevated IRT levels in the newborn’s blood may be due to premature birth or a stressful birth, so additional tests are needed to confirm the cystic fibrosis diagnosis.

If the blood test shows a high IRT level, genetic testing is performed for cystic fibrosis diagnosis. A positive result indicates that the baby has cystic fibrosis or is a carrier. To confirm the diagnosis, a sweat test is conducted shortly after.

Diagnosis for Children and Adults

For individuals who were not screened during pregnancy or at birth, various tests are available for cystic fibrosis diagnosis.

Sweat Test

The sweat test is considered the gold standard for diagnosing cystic fibrosis and is typically performed on individuals with typical cystic fibrosis symptoms. However, in cases with atypical clinical findings, chloride levels in sweat may not be sufficient for a definitive diagnosis. In rare cases, individuals with positive genetic tests may have negative sweat test results. Additionally, some other conditions can also lead to positive sweat test results.

Mutation Analysis – Genetic Testing

Mutation analysis is a test used for diagnosing cystic fibrosis by detecting specific genetic mutations associated with the disease. Scientists have identified more than 2,000 mutations that can potentially lead to cystic fibrosis by producing faulty forms of the cystic fibrosis protein. These mutations vary in frequency and distribution among different populations. While some mutations are rare, others are more common, particularly in certain ethnic groups. The mutation analysis panel for cystic fibrosis should have a mutation detection rate of over 95%. However, it’s important to note that in some populations, certain mutations may be very rare, making it challenging to achieve this detection rate.

Mutation testing for cystic fibrosis is usually conducted on a blood sample or a cheek swab. Results are typically available within three to five business days.

Cystic Fibrosis Lung Infection Diagnosis

Since the intensive treatment of respiratory infections is crucial for improving the life expectancy of cystic fibrosis patients, reliable methods are essential for diagnosing infections. Microbiological diagnosis of the organisms responsible for infections provides several benefits. Identifying pathogens allows for appropriate antibiotic treatment, improved bacterial eradication, enhanced clinical response, and reduced development of antibiotic resistance. Cultures obtained from lower respiratory tract secretions are ideal for guiding antibiotic therapy in cystic fibrosis-related lung disease. Sputum samples are used in older patients with advanced disease, while alternative techniques are utilized in young children or those who cannot produce sputum. These techniques include induced sputum, oropharyngeal swabs, nasopharyngeal secretions, and bronchoalveolar lavage samples.

Differential Tests in Cystic Fibrosis Diagnosis

Although most tests for cystic fibrosis provide definitive results, in some cases, the results may raise suspicions of other diseases. For example, asthma symptoms can mimic respiratory symptoms of cystic fibrosis. Since there are no specific diagnostic tests for asthma, the absence of mucus during an acute respiratory attack may help differentiate it from cystic fibrosis.

Bronchiectasis is a condition where damage to the lungs makes it difficult to clear mucus. While cystic fibrosis can cause bronchiectasis, pneumonia and tuberculosis can also lead to this condition. To distinguish between them, sputum testing can be performed to examine viruses, fungi, or bacteria separately, or tuberculosis may be assessed through blood or skin tests.

Similarly, celiac disease shares gastrointestinal symptoms with cystic fibrosis. It is typically distinguishable through intestinal biopsy. Additionally, individuals with celiac disease often see symptom improvement when gluten is removed from their diets.

Failure to thrive in infants refers to poor weight gain compared to expected growth. In some cases, inadequate nutrition can affect sweat test results positively. Additionally, the absence of respiratory symptoms can be an indicator that cystic fibrosis is not the cause.

Please note that the medical information provided is for general informational purposes only and should not be considered a substitute for professional medical advice. It is advisable to consult with a healthcare provider for specific diagnosis and treatment recommendations.