Mixed Messages: When the Sweat Test Is Negative but the Symptoms Look Like CF

The sweat test used to be the gold standard for determining whether a person has cystic fibrosis. With the advent of more definitive diagnostic procedures such as pre-implantation, prenatal and newborn screening for cystic fibrosis, getting a correct diagnosis is far easier than it used to be.

But what happens when you or your child still exhibits symptoms that are common to cystic fibrosis? How do you determine whether to keep pushing for more genetic testing to confirm CF, or whether it’s time for you and your doctor to start looking at other possibilities?

Here are the most common diseases that present with symptoms very similar to cystic fibrosis:

Shwachman-Diamond Syndrome (www.shwachman-diamond.org)

Diagnosed by: blood test or genetic test

• failure to thrive
• feeding problems
• recurrent infections
• slow growth
• Diarrhea with fatty, oily loose stools
• Blood clotting problems (similar to vitamin K deficiency in cystic fibrosis)
• Enlarged liver
• Diabetes mellitus
• Abnormal pulmonary function test

Celiac Disease (www.celiac.org)

Diagnosed by: 1) celiac blood panel 2) duodenal biopsy and biopsy of multiple locations in the small intestine 3) observed response to gluten free diet

• Recurring bloating, gas or abdominal pain
• Chronic diarrhea or constipation or both
• Unexplained weight loss
• Pale, foul-smelling stool
• Anemia
• Vitamin K deficiency
• Fatigue
• Failure to Thrive (infants)
• Male infertility

Primary Ciliary Diskinesia

Diagnosed by: biopsy of lung or sinus tissue

• Chronic sinusitis
• Bronchiectasis
• Susceptibility to pneumonia and lung infections
• Male infertility

Alpha-1 Antitrypsin Deficiency

Diagnosed by: simple blood test

• Impaired liver function
• Recurrent lung infections
• Airway inflammation
• Hemoptysis
• Swollen abdomen due to enlarged liver
• Wheezing and shortness of breath
• Chronic cough
• Bronchiectasis