History and exam
Key diagnostic factors
common
positive newborn screen
Elevated immunoreactive trypsinogen at birth followed by either a positive sweat test or genetic testing demonstrating two disease-causing mutations.
failure to pass meconium
From 10% to 20% of newborns with CF may have delayed passage of meconium or even bowel obstruction with meconium (meconium ileus).[33] In about 10% of these patients, there will be bowel perforation causing meconium peritonitis, which may be associated with a false-negative newborn screen.
failure to thrive
Poor weight gain and loss of percentiles, particularly in the presence of a voracious appetite.
Common in patients with untreated pancreatic insufficiency.
voracious appetite
Infants and children with untreated pancreatic insufficiency may never seem satiated due to malabsorption.
wet-sounding cough
Patients may present with prolonged colds and coughing, particularly with hard coughing spells.
It is a common symptom, particularly when diagnosis is made after infancy.
recurrent infection
Patients may present with a history of recurrent lower airways infections, either bronchitis or pneumonia, necessitating antibiotic therapy.
chronic rhinosinusitis
Patients may present with chronic or recurrent symptomatic rhinosinusitis. In some circumstances these symptoms may be confused with or even overlap allergic-mediated disease.
genital abnormalities in males
In males, exam of the scrotum reveals bilateral absence of the vas deferens.
uncommon
hemoptysis
Patients may demonstrate minor hemoptysis (e.g., blood-streaked sputum) or major hemoptysis (>300 cc/24 hours) during a pulmonary exacerbation, with major hemoptysis more common in the presence of advanced lung disease.
Other diagnostic factors
common
malabsorptive stool with steatorrhea
Pancreatic-insufficient patients may have bulky, greasy, foul-smelling stools that float in the toilet bowl, as a result of fat malabsorption.
digital clubbing
Patients may have a rounding of the nail bed of the fingers and toes where the nail bed meets the cuticle. The cause of clubbing remains unknown. Although more common in CF patients than in people without CF, clubbing of the digits is not a pathognomonic sign.
gastroesophageal reflux
Patients with CF may have more gastroesophageal reflux than those without CF.
uncommon
wheeze
Patients may present with wheezing and air trapping due to airway obstruction.
This is not particularly common unless there is concomitant asthma or allergic bronchopulmonary aspergillosis.
increased anteroposterior (AP) diameter of the chest
Patients with lower airways obstruction as a result of mucus retention, infection, and inflammation may demonstrate an increased AP chest diameter due to air trapping.
It is uncommon in patients before lung disease. It is common as lung disease progresses.
history of pancreatitis
Patients with pancreatic sufficiency may present with recurrent pancreatitis. Symptoms may include acute abdominal pain, nausea, and vomiting. Laboratory values will show elevated serum amylase and lipase.
history of acute appendicitis
Patients with CF may present with acute appendicitis, which symptomatically is not different in CF than in other patients. However, symptoms may overlap or be confused with other comorbidities of CF, including distal intestinal obstruction syndrome (DIOS) and intussusception.
enlarged liver or spleen
CF is associated with a range of liver diseases, from asymptomatic periportal inflammation to focal biliary cirrhosis. Physical exam will often reveal an enlarged liver, enlarged spleen, or both. This is commonly found in older patients.
Risk factors
strong
family history of CF
A positive history of CF in the family should raise the level of suspicion of CF in the patient. The family history may reveal a distant relative who died because of a respiratory disease reminiscent of CF.
known carrier status of both parents
If both parents are known carriers of mutant cystic fibrosis transmembrane conductance regulator (CFTR) alleles, then each child conceived by those parents will have a 1 in 4 chance of having CF.
ethnicity
CF is most common in people of white ethnicity.[4][5] Between 1 in 25 and 1 in 30 white people is thought to be a carrier of a cystic fibrosis transmembrane conductance regulator (CFTR) mutation, and the incidence of CF births is between 1 in 3000 and 1 in 6000.[4][26][27] Incidence of CF is less, but still significant, in African-Americans and Hispanic people. It is rarer in people of Asian descent.[4]
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