How is cystic fibrosis (CF) diagnosed?

Updated: Oct 22, 2019
  • Author: Girish D Sharma, MD, FCCP, FAAP; Chief Editor: Kenan Haver, MD  more...
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Suspect CF in patients with fetal or neonatal bowel obstruction and perform diagnostic tests as soon as possible.

From 75 to 80% of males with congenital bilateral absence of vas deferens (CBAVD) have been shown to possess a CFTR mutation for CF. With this condition, one may palpate the epididymis head; however, the structures derived from the Wolffian ducts under the control of the gonads, caudal epididymis, and vas deferens are absent. This anomaly may prove useful when looking for immediate support regarding a diagnosis of CF.

In adult males, obstructive azoospermia, in the absence of any other obvious cause (eg, vasectomy), provides additional corroborative evidence for the diagnosis of CF. Confirm results from semen analysis by obtaining a testicular biopsy.

A diagnosis of CF should be confirmed or refuted by a sweat test that meets all National Committee for Clinical Laboratory Standards (NCCLS) criteria. A sweat test may be performed any time after the first 48 hours of life if the neonate is not edematous.

Mutation analysis, performed on buccal or on blood cells using a Guthrie card, helps confirm the diagnosis if it yields at least one known CF mutation. Refer patients with confirmed CF to a regional or satellite CF center for counseling and education about this complex chronic disease. CF center physicians can also assist in postoperative management of nutritional or respiratory problems. To obtain a list of accredited centers, call 1-800-FIGHT CF or see the Cystic Fibrosis Foundation Web site.

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