Cystic Fibrosis

Diagnostic triad: cough + failure to thrive + loose bowel motions. Affects 1 in 2,500 Caucasians. Newborn screening detects 75% of cases.

All couples planning a pregnancy, or who have already conceived and are in the first trimester, should be advised about the availability of reproductive carrier screening for CF, spinal muscular atrophy (SMA) and Fragile X syndrome (FXS). Medicare rebates apply to this screening, covering CF, SMA and FXS. MBS item 73451 covers initial screening of the female partner who is pregnant or planning pregnancy. MBS item 73452 covers subsequent screening of the male reproductive partner for CF or SMA if detected in the female.

Pathophysiology and clinical features

Defect in chloride ion channel protein, causing hypertonic and thick secretions. Affects the lungs, pancreas and gut.

Malaise, failure to thrive, exercise intolerance. Recurrent respiratory infections (including nasal polyps). GI: pale loose bulky stools, malabsorption, pancreatic insufficiency.

Historical mean age of death was 31 years — now substantially out of date for patients on CFTR modulator therapy, see below.

Diagnosis

Cystic fibrosis newborn screening commenced in NSW in 1981 as part of the state’s screening program. About 84% of infants with an initial positive newborn screen do not actually have cystic fibrosis. Around 10% of people with CF are diagnosed as adults, mostly due to limitations of earlier newborn screening programs.

Sweat test shows elevated chloride and sodium. DNA testing identifies carriers.

Treatment

CFTR modulator therapy — the single biggest change to CF management since this note was written. Elexacaftor/tezacaftor/ivacaftor (brand Trikafta/Kaftrio) directly targets the underlying chloride-channel defect rather than just managing its downstream effects, and has been PBS-listed in Australia since 2022 for eligible genotypes (roughly 90% of people with CF carry at least one copy of the F508del mutation these drugs target). Earlier-generation modulators (ivacaftor alone, lumacaftor/ivacaftor) predate this note but cover a smaller genotype range. These modulators act by improving production, intracellular processing and/or function of the defective CFTR protein. They are available on the PBS under the Section 100 (S100) highly specialised drugs scheme. Prescriptions for CFTR modulator medications are written by the specialist CF team and can be supplied by a community pharmacy. CFTR modulators improve lung function, nutritional status and quality of life; per the Australian Cystic Fibrosis Data Registry, median survival has already increased from 49 years for those born 2005–2009 to 56 years for those born 2016–2020, and continues to extend further with modulator therapy. This changes the overall prognostic framing of the diagnosis, not just one treatment line.

Standard supportive care continues alongside modulator therapy: treat respiratory infections, chest physiotherapy for secretions, and hypertonic saline for chest secretions.

Most patients with CF have pancreatic insufficiency and require enzyme replacement therapy. Creon is the only enzyme preparation available in Australia. As a guide, the dose is 5,000 lipase units per 3 to 4g of fat and usually not more than 10,000 lipase units/kg per day, tailored to the individual by the CF physicians and dietitian. Enzyme replacement therapy is available on the general schedule of the PBS and can be prescribed by general practitioners for continuing therapy.

Follow-up

Adults with suspected or confirmed CF are referred for non-urgent respiratory assessment; children to the paediatric respiratory CF clinic. People with CF require regular multidisciplinary review, including lung function tests at least annually, nutritional screening blood tests annually, and screening for CF-related diabetes with HbA1c or an oral glucose tolerance check. Colonoscopy is recommended from age 35 years.