Diagnosis

The are a variety of measures in place to test for Cystic Fibrosis.  All newborns in the United States are screened for CF by either a blood test or a genetic test.  The blood test assesses pancreas function, while the genetic test indicates whether the CFTR gene is faulty.  If one of these newborns screenings indicates an abnormality, the infant will undergo a sweat test between two and four weeks of life.  During the sweat test, a technician will apply a chemical solution to a small area of the arm or leg.  This chemical does not pose a risk to the child.  An electrode is placed on the area and a mild electric current is applied to induce sweating.  This part of the procedure takes about 5 minutes and the child may feel some tingling or warmth, but it is not strong enough to cause pain or damage.  The sweat is collected on a piece of filter paper or gauze and then sent to the lab for evaluation. The lab is checking for chloride levels in the infant's sweat.  Some physicians may order the test to be performed twice for verification.  This test is safe and reliable.  It has been the "Gold Standard" in CF diagnosis for over fifty years.  The entire test takes about an hour, but may take longer.  The child should not have lotion or ointment applied to the skin for 24 hours before the test.  Otherwise no changes in diet or medications need to be made.  Once a positive or negative result has been confirmed, the results will not change in later sweat tests.  Other diagnostic tools include chest x-Ray, sinus x-Ray, lung function tests and sputum culture.  These tests are more helpful is analyzing the progress of the disorder once a diagnosis has been confirmed.


Sources: National Institutes of Health and Cystic Fibrosis Foundation

Etiology and Pathophysiology

To fully understand the causation and progression of Cystic Fibrosis, it is helpful to have a visual representation of the disease.  Khan Academy presents a clear and concise visual summary of CF.

https://www.khanacademy.org/science/health-and-medicine/respiratory-system-diseases/cystic-fibrosis/v/what-is-cystic-fibrosis

Who has it?

Throughout the world, approximately 70,000 children and adults suffer from Cystic Fibrosis.  Almost half of these cases (30,000) are within the United States.  Both males and females of all races and ethnicities are at risk, but CF is most prevalent in Caucasians of Northern European descent.   About 1,000 new cases are diagnosed in the US each year.  Historically, about half of the CF population is diagnosed by five months of age, and over 75% are diagnosed before their second birthday.  However, some people with less severe cases have been diagnosed well into adulthood.  Diagnosis has been evolving over the past few years, and now all states screen newborns for cystic fibrosis within a few days of birth.  The screening is not 100% accurate, and produces many false positive.  False positives occur when a healthy baby is tested for a disease and the results indicate that the baby has the disease.  To find out if the results were accurate or not, all newborns who test positive for CF go through a follow-up test that is more accurate.  This secondary screening rules out CF in over half of those who tested positive in the initial newborn screening.  Because of the recent implementation of newborn screening, more cases are being confirmed at an early age, improving treatment outcomes and documentation of CF epidemiology. 

It is believed that CF susceptibility is entirely genetic.  However, the severity of the illness is affected by many environmental factors including air quality, exposure to bacteria, access to medical care and age of diagnosis and treatment.  These factors, along with genetics and others health conditions determine the lifespan of each CF patient.  There is no cure for the disease, but people with CF who maintain successful treatment regimens can live into their fifties with reasonably high quality of life.  This possibility is a thrilling advancement in comparison with CF outcomes in 20 years ago.  CF was considered a childhood disease in recent years because so few patients lived into adulthood.  Today almost half of those with CF are 18 or older.  According to a recent article published by BMC Pulmonary Medicine, this improvement is due to earlier diagnosis and follow-up treatment over the past two decades.  The results point toward newborn screening as a major indicator in disease outcome.







Citations

Cystic Fibrosis. http://www.nhlbi.nih.gov/health/health-topics/topics/cf.  Published December 26, 2013.  Accessed January 16, 2015.

Marson FA, Hortencio TD, Aguiar KC, Ribeiro JD. Demographic, clinical, and laboratory parameters of cystic fibrosis during the last two decades: a comparative analysis. BMC Pulmonary Medicine. 2015; 15(3). doi:10.1186/1471-2466-15-3 

O’Sullivan BP, Freedman SD. Cystic fibrosis. Lancet 2009;373:1891–1904.

What is Cystic Fibrosis?

Cystic Fibrosis (CF) is a genetic disorder that affects the lungs, gastrointestinal tract, pancreas, liver, kidney, and reproductive organs through overproduction of secretions. It is most commonly associated with increased sputum production and frequent lung infections. Other common symptoms include shortness of breath, sinus infections, stunted growth, gastrointestinal ileus, and infertility. There is no cure for CF, but some patients are eligible for lung transplant for improved respiratory function and other treatments are available for symptom management. The average life expectancy for a CF patient is just under 40 years, and most CF deaths are related to the lungs.

CF is classified as an autosomal recessive disorder. It is determined by the functionality of the gene CTFR. CTFR is responsible for bodily secretions including sweat, saliva, mucus, and digestive juices. When this gene is mutated, the thin, slippery secretions of the body become thick and sticky, creating a barrier to normal bodily functions. Most healthy people have two normal copies of the gene CTFR. Some people have one normal copy and one abnormal copy. These people are termed “carriers” and they do not have any CF symptoms. When two carriers procreate, there is a 25% chance that the offspring will inherit both abnormal genes and have cystic fibrosis. Currently about 30,000 Americans suffer from CF. In the United States, it is most common in Caucasians, followed by Hispanics, Native Americans, African Americans, and least common in Asian Americans.

In the past, CF has been considered a childhood disease, primarily because most CF patients did not live into adulthood, and those who did weren’t able to maintain a job and live independently. In 1959, the average survival of a CF patient was just 6 months. Thanks to recent advancements in treatment and management, CF is no longer a childhood death sentence. Many people are able to live into adulthood with well-managed symptoms that allow for a relatively normal lifestyle. For unknown reasons, men with CF live an average of 40 years in the United States, while women average about 37 years. Some parts of the world screen infants for CF at birth, but the test is not completely accurate, so testing has become controversial. CF is currently undergoing extensive research due to recent increased funding and is a very exciting topic in the field of medicine.

Sources
http://www.nhlbi.nih.gov/health/health-topics/topics/cf.  Published December 26, 2013.  Accessed January 10, 2015.

http://www-uptodate-com.offcampus.lib.washington.edu/contents/cystic-fibrosis-clinical-manifestations-and-diagnosis?source=search_result&search=cystic+fibrosis&selectedTitle=1%7E150 Published June 25, 2014.  Accessed January 10, 2015.