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Cystic Fibrosis (CF)

NICE guideline [NG78] Cystic fibrosis: diagnosis and management. Published: Oct 2017.

Background Information

Possible CF complications categorised by body system:
 
Body system Complications
Respiratory
  • Sinusitis and nasal polyps
  • Chronic lung infections
  • Bronchiectasis
GI
  • Meconium ileus (in newborn), distal intestinal obstruction syndrome (in adults)
  • Fat-soluble vitamin deficiency (A D E K)
  • Chronic liver disease
  • Underweight / malnutrition
Metabolic
  • Diabetes (secondary) (affects up to 50% adults)
  • Osteoporosis
Reproductive
  • Male infertility (obstructive zaaospermia) - almost all males with CF are infertile
  • Female subfertility
Genitourinary
  • Urinary stress incontinence
 

Guidelines

CF is routinely screened in noewborns with the spot (heel-prick) test at ~5 days old

The screening marker is immunoreactive trypsinogen (IRT)
  • An abnormal screening test is NOT diagnostic
  • These newborns should undergo a sweat chloride test as outlined below

If CF is suspected:
  • Children and young people → sweat chloride test 
    • ↑ Sweat chloride level is indicative of CF
    • ≥60 mmol/L is a common diagnostic threshold
 
  • Adults → CF gene test

 

Although not explicitly mentioned in NICE guideline, the sweat chloride test is considered the gold standard diagnostic test for CF.

The increased sweat chloride reflects the underlying CFTR protein defect. While genetic testing may not detect some uncommon CF mutations.

CF is a multi-system condition, therefore the management can be splited accordingly. 
 

Offer to all patients:
  • Individualised exercise programme
  • Airway clearance techniques
    • If unable to use standard airway clearance techniques → consider non-invasive ventilation
 
  • Mucoactive agent
    • 1st line: rhDNase (dornase alfa) (recombinant human deoxyribonuclease)
    • 2nd line: hypertonic sodium chloride +/- rhDNase
    • 3rd line: inhaled mannitol dry powder

CFTR modulators are not routinely offered to all patients, but only those with F508 deletion mutation in the CFTR gene. Examples:
  • Lumacaftor-ivacaftor
  • Tezacaftor–ivacaftor
  • Ivacaftor–tezacaftor–elexacaftor

Note this is a simplification of the exact NICE technology apprasial guidance.

Antibiotic prophylaxis:
  • Flucloxacillin in children up to 3 y/o, consider up to 6 y/o
  • Long-term azithromycin if there is deteriorating lung function or repeated pulmonary exacerbation
    • As azithromycin have additional immunomodulatory and anti-inflammatory properities that reduces airway inflammation beyond its antibiotic effects

Choice of antibiotic for common infective organisms in CF:
 
Organism Choice of antibiotic
Pseudomonas aeruginosa
  • Tobramycin
  • Clistimethate sodium
  • Ciprofloxacin
Staphylococcus aureus
  • Flucloxacillin
MRSA
  • Vancomycin
  • Linezolid
Haemophilus influenzae
  • Co-amoxiclav
  • Azithromycin
 

Perform the following at each review:
  • Oxygen saturation
  • Chest X-ray
  • Blood tests, including white cell count, aspergillus serology and serum IgE
  • Respiratory samples (ideally sputum, or else cough swab or nasal pharyngeal aspirate) for microbiology investigations
  • Spirometry including FEV1Forced expiratory volume in 1 second, FVCForced vital capacity, FEFForced expiratory flow

Consider low-dose chest CT for children who have not had one before (can help detect early bronchiectasis).

  • Increase calorie intake by eating high-energy food and increase portion size (if there is weight loss and inadequate weight gain)
  • Oral nutritional supplements (esp. fat soluble vitamins)

Use stool elastase estimation to test for exocrine pancreatic insufficiency
  • Offer oral pancreatic enzyme replacement therapy to those with exocrine pancreatic insufficiency
  • Consider acid suppression agent (PPIProton pump inhibitor or H2 receptor antagonist) if there is persistent malabsorption despite optimal pancreatic enzyme replacement therapy

Test for CF-related diabetes yearly from 10 y/o onwards with
  • Continuous glucose monitoring, or
  • Serial glucose testing over a few days, or
  • OGTTOral glucose tolerance testing

Perform yearly LFTs, if abnormal:
  • Liver ultrasound scan, and
  • Consider ursodeoxycholic acid

Typical presentation:
  • Vomiting and abdominal distension
  • Palpable mass in right lower quadrant (from faecal loading)

Investigate with abdominal ultrasound or abdominal CT

Management:
  • Ensure adequate hydration with oral or IV fluids
  • 1st line: gastrografin (diatrizoate meglumine and diatrizoate sodium solution) orally or via enteral tube
  • 2nd line: macrogols ( iso-osmotic polyethylene glycol and electrolyte solution) orally or via enteral tube
  • Last resort: surgery

To reduce risk of recurrence:
  • Encourage to drink plenty of fluids
  • Optimise pancreatic enzyme replacement therapy
  • Consider regular stool-softening agent (e.g. lectulose)

References

Author: Noah T
Reviewer:
Last edited: 30/07/25