Diagnosis Cystic Fibrosis: Early Detection, Tests, and What to Expect

Cystic fibrosis (CF) is a genetic disorder that primarily affects the lungs, pancreas, liver, intestines, sinuses, and sex organs. Early and accurate Diagnosis Cystic Fibrosis is crucial for initiating timely treatment and improving the quality of life for individuals affected by this condition. This article will delve into the methods and processes involved in diagnosing cystic fibrosis, from newborn screenings to diagnostic tests for older children and adults.

Understanding Cystic Fibrosis and its Genetic Basis

Cystic fibrosis is caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. This gene is responsible for producing a protein that controls the movement of salt and water in and out of the body’s cells. In individuals with CF, the mutated CFTR gene leads to the production of a faulty or missing CFTR protein. This malfunction disrupts the normal flow of salt and water, resulting in the production of thick, sticky mucus that can clog various organs and lead to a range of symptoms and complications.

CF is an autosomal recessive genetic disorder, meaning an individual must inherit two copies of the mutated CFTR gene – one from each parent – to develop the condition. Individuals who inherit only one copy of the mutated gene are known as carriers. Carriers typically do not exhibit symptoms of CF but can pass the mutated gene on to their children.

Newborn Screening for Cystic Fibrosis: The First Step

Universal newborn screening for cystic fibrosis is now standard practice in every state in the United States. This proactive approach to diagnosis cystic fibrosis allows for the identification of affected infants shortly after birth, often before symptoms even appear. Early diagnosis through newborn screening is vital as it enables healthcare professionals to initiate treatment promptly, which can significantly improve long-term health outcomes.

The primary test used in newborn screening for CF is the immunoreactive trypsinogen (IRT) test. This blood test measures the level of IRT, a protein produced by the pancreas, in a newborn’s blood. A small blood sample is typically collected from the baby’s heel. Elevated IRT levels can be indicative of cystic fibrosis, as the thick mucus in the pancreas of infants with CF can block the release of digestive enzymes, leading to an increase in IRT in the blood.

It’s important to note that a positive newborn screen, indicated by a high IRT level, does not definitively mean that a baby has cystic fibrosis. Elevated IRT levels can also occur in premature infants or babies who experienced a stressful delivery. Therefore, a positive newborn screen necessitates further diagnostic testing to confirm or rule out a diagnosis cystic fibrosis.

Confirmatory Diagnostic Tests for Cystic Fibrosis

If a newborn screening test indicates a potential risk for cystic fibrosis, or if older children or adults present with symptoms suggestive of CF, further diagnostic tests are essential to establish a definitive diagnosis cystic fibrosis. The sweat chloride test and genetic testing are the primary confirmatory tests used to diagnose CF.

Sweat Chloride Test: The Gold Standard for Diagnosis

The sweat chloride test is considered the gold standard for diagnosis cystic fibrosis. This test measures the concentration of chloride in sweat. Individuals with CF have a higher-than-normal amount of salt (sodium chloride) in their sweat due to the faulty CFTR protein’s inability to properly regulate salt and water movement across cell membranes.

The sweat test is typically performed when a baby is at least two weeks old. A chemical called pilocarpine is applied to a small area of the baby’s skin to stimulate sweat production. An electrode is then attached to the area to further encourage sweating. The sweat is collected on filter paper or in a plastic coil for approximately 30 minutes. The collected sweat sample is then analyzed to measure the chloride concentration.

Results of the sweat chloride test are interpreted as follows:

• Normal: Chloride concentration is less than 30 millimoles per liter (mmol/L). CF is unlikely.
• Intermediate: Chloride concentration is between 30 and 59 mmol/L. Further testing, such as genetic testing or repeat sweat tests, may be recommended, especially in infants with a positive newborn screening or symptoms suggestive of CF.
• High (Diagnostic for CF): Chloride concentration is 60 mmol/L or greater. This result is consistent with a diagnosis cystic fibrosis.

It is crucial that sweat tests are performed at a Cystic Fibrosis Foundation-accredited care center to ensure accurate and reliable results.

Genetic Testing: Identifying CFTR Gene Mutations

Genetic testing plays an increasingly important role in diagnosis cystic fibrosis. Genetic tests analyze a person’s DNA to identify mutations in the CFTR gene. Genetic testing can be used in conjunction with newborn screening and sweat chloride testing to confirm a CF diagnosis. It can also be used to:

• Confirm CF diagnosis: In cases where sweat test results are intermediate or inconclusive, genetic testing can help clarify the diagnosis. Identifying two CF-causing mutations in the CFTR gene supports a diagnosis cystic fibrosis.
• Identify CF carriers: Genetic testing can determine if an individual is a carrier of a CFTR gene mutation. This is particularly relevant for family planning, especially when both partners are known to be or suspected of being carriers.
• Guide treatment decisions: Specific CFTR gene mutations can influence the severity of the disease and the response to certain CFTR modulator medications. Identifying the specific mutations can help healthcare professionals personalize treatment strategies.

Genetic testing for CF can be performed using a blood sample or saliva sample.

Diagnosing Cystic Fibrosis in Older Children and Adults

While newborn screening has significantly increased the rate of early diagnosis cystic fibrosis, some individuals may not be diagnosed until later in childhood or even adulthood. There are several reasons for delayed diagnosis:

• Prior to newborn screening: Before universal newborn screening became widespread, individuals with milder forms of CF might not have been diagnosed in infancy.
• Atypical or mild CF: Some individuals may have CFTR gene mutations that result in milder symptoms that are not immediately recognized as CF in early childhood.
• Misdiagnosis: Symptoms of CF can sometimes overlap with other conditions, leading to initial misdiagnosis.

In older children and adults, a diagnosis cystic fibrosis may be considered when individuals present with symptoms such as:

• Persistent respiratory problems: Chronic cough, wheezing, recurrent lung infections, bronchiectasis (damaged and widened airways).
• Digestive issues: Pancreatitis (inflammation of the pancreas), malabsorption (difficulty absorbing nutrients), meconium ileus (intestinal blockage in newborns).
• Nasal polyps and chronic sinus infections.
• Male infertility (due to congenital absence of the vas deferens).
• Salty-tasting skin.

The diagnostic process for older children and adults suspected of having CF typically involves a sweat chloride test and genetic testing, similar to the confirmatory testing done in newborns. Healthcare professionals will also review the individual’s medical history, symptoms, and conduct a physical examination.

The Diagnostic Process: What to Expect

The process of diagnosis cystic fibrosis involves several steps, often requiring collaboration between different healthcare professionals. Here’s what you can generally expect:

1. Initial Assessment: If CF is suspected based on newborn screening, symptoms, or family history, the healthcare provider will conduct an initial assessment. This includes reviewing medical history, family history of CF, and current symptoms.
2. Physical Examination: A thorough physical examination will be performed to assess for signs and symptoms of CF, such as lung sounds, growth patterns, and other physical indicators.
3. Sweat Chloride Test: If CF is still suspected, a sweat chloride test will be ordered. It’s crucial to have this test performed at a certified CF care center.
4. Genetic Testing: Genetic testing may be recommended to confirm the diagnosis, especially if sweat test results are borderline or to identify specific CFTR mutations.
5. Multidisciplinary Care Team: Once a diagnosis cystic fibrosis is confirmed, individuals will be referred to a multidisciplinary CF care team. This team typically includes pulmonologists, gastroenterologists, dietitians, respiratory therapists, nurses, social workers, and other specialists who work together to provide comprehensive care.

Importance of Early Diagnosis and Ongoing Care

Early diagnosis cystic fibrosis, particularly through newborn screening, is critical for several reasons:

• Prompt Treatment Initiation: Early diagnosis allows for the immediate initiation of treatments aimed at managing symptoms, preventing complications, and slowing disease progression.
• Improved Nutritional Status: Early intervention can address digestive issues and ensure adequate nutrition, which is vital for growth and overall health in children with CF.
• Prevention of Lung Damage: Starting airway clearance therapies and managing lung infections early can help minimize lung damage and preserve lung function.
• Enhanced Quality of Life: Early and comprehensive care can significantly improve the quality of life for individuals with CF, allowing them to live fuller, healthier lives.

Even with early diagnosis and advancements in treatment, cystic fibrosis is a chronic condition that requires ongoing management and monitoring throughout life. Regular visits to a CF care center, adherence to prescribed therapies, and proactive management of symptoms are essential for maintaining health and well-being.

Conclusion: Hope and Progress in Cystic Fibrosis Diagnosis and Care

Diagnosis cystic fibrosis has significantly advanced with universal newborn screening and improved diagnostic testing methods. Early detection and comprehensive care have transformed the prognosis for individuals with CF, leading to increased life expectancy and improved quality of life. While there is currently no cure for CF, ongoing research and the development of new therapies, particularly CFTR modulators, offer hope for even more effective treatments and potentially a cure in the future. If you suspect you or your child may have symptoms of cystic fibrosis, it is crucial to seek medical evaluation and discuss diagnosis cystic fibrosis with your healthcare provider.

Request an appointment

References:

1. Cystic fibrosis. National Heart, Lung, and Blood Institute. https://www.nhlbi.nih.gov/health/cystic-fibrosis. Accessed Aug. 8, 2024.
2. Bronchiectasis. National Heart, Lung, and Blood Institute. https://www.nhlbi.nih.gov/health/bronchiectasis. Accessed Aug. 8, 2024.
3. FAQs: Cystic fibrosis: Prenatal screening and diagnosis. American College of Obstetricians and Gynecologists. https://www.acog.org/womens-health/faqs/cystic-fibrosis-prenatal-screening-and-diagnosis. Accessed Aug. 8, 2024.
4. Ferri FF. Cystic fibrosis. In: Ferri’s Clinical Advisor 2025. Elsevier; 2025. https://www.clinicalkey.com. Accessed Aug. 8, 2024.
5. Kliegman RM, et al., eds. Cystic fibrosis. In: Nelson Textbook of Pediatrics. 22nd ed. Elsevier; 2025. https://www.clinicalkey.com. Accessed Aug. 8, 2024.
6. Kellerman RD, et al. Cystic fibrosis. In: Conn’s Current Therapy 2024. Elsevier; 2024. https://www.clinicalkey.com. Accessed Aug. 8, 2024.
7. Lockwood CJ, et al., eds. Respiratory diseases in pregnancy. In: Creasy and Resnik’s Maternal-Fetal Medicine: Principles and Practice. 9th ed. Elsevier; 2023. https://www.clinicalkey.com. Accessed Aug. 8, 2024.
8. Ong T, et al. Cystic fibrosis: A review. JAMA. 2023; doi:10.1001/jama.2023.8120.
9. Rubin R. Tackling the misconception that cystic fibrosis is a “white people’s disease.” JAMA. 2021; doi:10.1001/jama.2021.5086.
10. Care centers. Cystic Fibrosis Foundation. https://www.cff.org/managing-cf/care-centers. Accessed Aug. 8, 2024.
11. Trikafta (prescribing information). Vertex Pharmaceuticals Inc.; 2023. https://www.trikafta.com/. Accessed Aug. 8, 2024.
12. Symdeko (prescribing information). Vertex Pharmaceuticals Inc.; 2023. https://www.symdeko.com/. Accessed Aug. 8, 2024.
13. Orkambi (prescribing information). Vertex Pharmaceuticals Inc.; 2023. https://www.orkambi.com/. Accessed Aug. 8, 2024.
14. Kalydeco (prescribing information). Vertex Pharmaceuticals Inc.; 2023. https://www.kalydeco.com/. Accessed Aug. 8, 2024.
15. Pilewski JM. Update on lung transplantation for cystic fibrosis. Clinics in Chest Medicine. 2022; doi:10.1016/j.ccm.2022.07.002.
16. Fridell JA, et al. Pancreas transplantation for cystic fibrosis: A frequently missed opportunity. Clinical Transplantation. 2021; doi:10.1111/ctr.14371.
17. Wadsworth LE, et al. Non-invasive ventilation is associated with long-term improvements in lung function and gas exchange in cystic fibrosis adults with hypercapnic respiratory failure. Journal of Cystic Fibrosis. 2021; doi:10.1016/j.jcf.2021.05.011.
18. Allscripts EPSi. Mayo Clinic.
19. Chalmers SJ (expert opinion). Mayo Clinic. Oct. 18, 2024.