This presentation will surely help the general physicians and paediatricians to understand the symptoms of cystic fibrosis and will educate regarding various diagnostic modalities in cystic fibrosis

1. How and when to
diagnose
Cystic Fibrosis ?
Dr. Kaustubh Mohite

2. Case 1:
• 1 year old, male child.
• Born out of consanguineous marriage.
• Birth weight – 2.4 kg
• Mother gives history that the child did not pass stool in the first 24 hours and later passed only
after giving enema.
• In the past 1 year, the child has been hospitalized 3 times for pneumonia requiring IV antibiotics for
7 – 10 days.
• Passes stools which are oily in consistency and stains the diaper.
• Has persistent cough since 6 months of age which has recently increased.

3. On Examination:
• Height and Weight < 3rd centile.
• Mild baseline tachypnea present.
• Child has bouts of wet cough.
RS:
• Air entry decreased in bilateral bases
• Bilateral wheeze and crepitations heard
You get a chest Xray:

4. Case 2:
• 8-year-old male child
• Complains of recurrent episodes of wet cough lasting for 2-3 weeks
• Has received multiple courses of oral antibiotics after which cough relatively subsides.
• Presently brought for complains of wet cough, fever, hurried breathing.
• No GI complains.

5. On Examination:
• Height and weight < 3rd centile
• Febrile
• Significant tachycardia and tachypnea for age
• SpO2 – 86% on room air
RS:
• RR – 45 – 50 / min
• Air entry reduced in right infra-scapular region
• Bilateral significant crepitations heard.

6. Case 3:
• 12 year old girl.
• Sister of case 2
• Was apparently all right till 10 years of age.
• Later she observed that she used to pass oily, greasy stools after consumption of high fat diet.
• On and off non-significant cough.
On Examination:
• Weight – 3rd to 50th centile for age, Height normal for age
• Vitals stable
• Chest clear of auscultation.

7. Case 1 Case 2 Case 3
1 year old 8 years old 12 years old
Respiratory complains + Respiratory complains + -
GI complains + - GI complains +
FTT + FTT + -
Born of Consanguineous
marriage
- -
- - Positive family history
- In acute Exacerbation -
All should be suspected to have Cystic Fibrosis
However, All have different severity of disease

8. Today’s focus:
• What is Cystic Fibrosis ?
• What is the basic underlying problem in this disease ?
• How does a child present ?
• How do you confirm the diagnosis ?
• How do you categorize CF patients ?
• Importance of early diagnosis and management

9. What is Cystic Fibrosis ?
Cystic Fibrosis is an Autosomal recessive genetic disorder
caused due to mutation in the CFTR (Cystic Fibrosis
Transmembrane Conductance Regulator) gene causing
reduction in airway surface liquid (ASL) hydration, causing
difficulty to clear airway pathogens which eventually increases
infection and inflammation.

11. Pathophysiology of CF:
CFTR protein channel has got 3 main function:
• Efflux of Chloride ions.
• Influx of Sodium ions.
• Transport of Bicarbonate ions.
CF

12. In CF patients:
Because of absent of reduced CFTR activity:
• Downregulation of chloride transport across the channel.
• Upregulation of Sodium (ENaC) channel.
• Decreased efflux of bicarbonate ions (acidification of airway
secretions)
Water molecules move along with sodium molecules leading to hyper-
concentration of mucus.

14. Clinical Manifestations:
Age wise
System
wise

15. Age wise features:
0 -2
years
Failure to
thrive
Steatorrhea
Recurrent
chest
infections
Meconium
ileus
Rectal
prolapse
Prolonged
neonatal
jaundice

16. 3 – 16
years
Recurrent
chest infection
Idiopathic
Bronchiectasis
Steatorrhea
Nasal polyps /
sinusitis
Intestinal
obstruction
Positive family
history

17. Adulthood
Azoospermia
Bronchiectasis
Chronic
Sinusitis
ABPA
Biliary
cirrhosis
Diabetes
Mellitus
Portal
Hypertension
Cholestasis

18. System wise clinical features:

19. Diagnostic criteria:

20. Diagnostic modalities:
1. Newborn Screening
2. Sweat Chloride test
3. Nasal Potential Difference
4. Genetic analysis
5. Assessment of end organ effects

21. Newborn Screening
• This test measures the amount of trypsinogen in the blood.
Trypsinogen
Trypsin
Breakdown of
complex proteins
into peptides

22. In CF patients:
Trypsinogen
• Mucus plugs block the pancreatic ducts, preventing trypsinogen from reaching
the small intestine, resulting in decreased breakdown of food proteins.
• As there is no conversion of trypsinogen to trypsin, levels of Trypsinogen
increases in the blood.

23. • 586 cases diagnosed with CF from 1971 to 2014
• 20 year and 30 year survival was analyzed along with quality of life.
• Significant improvement was observed in cases with CF diagnosed at early age by NBS.
2017

24. Sweat Chloride test
• Gold standard for the diagnosis of CF.
• 3 ways of conducting this test:
• Gibson and Cooke technique
• Nanoduct technique
• Macroduct technique (most sophisticated)

25. Patient selection:
• Child should be more than 2 weeks of age.
(transient elevation of sweat chloride in first 1 week of age)
• Greater than 3 kg.
• Normally hydrated
• No significant systemic illness

26. Video on the procedure of sweat
chloride analysis by macroduct
technique
• https://www.youtube.com/watch?v=4UI_G-DjEoo&t=7s

27. Add on points:
• Normal adolescents and adults tend to have higher sweat chloride
levels (up to 60 mmol/L), hence borderline values in this age group
may not reflect CF.
• Some atypical CF mutations may have normal to intermediate values
of sweat chloride levels.
• Commonest cause of false positive test is operator inexperience,
followed by eczematous skin.
• Levels greater than 150 mmol/L are not physiological and should be
repeated.

28. 2018
• Cystic Fibrosis Foundation changed the intermediate sweat chloride concentration range
from 40–59 mmol/L to 30–59 mmol/L for age > 6 months.
• They revisited sweat chloride test results (n = 3012) in the last 5 years at Texas Children's
Hospital
• They identified 125 that would be reclassified.
• 8 of them were found to have 2 disease causing CFTR mutation and developed full blown
disease.
• They conclude that sweat chloride concentration in combination with CFTR genetic analysis
enhances the probability of identifying individuals that have risk of developing CF.

29. Osmolarity and Conductivity of sweat:
• Osmolarity of sweat records the total solute concentration in mmol/Kg of
sweat.
• Values:
• > 200 mmol/Kg – CF
• 150 – 200 mmol/Kg – equivocal
• 50 – 150 mmol/Kg – normal
• Conductivity represents a non-selective measurement of ions and has a
good correlation with sweat chloride levels.
• Values:
• Cut-off for CF - > 90 mmol/L
• Normal - < 75 mmol/L
• Upper physiological limit – 170 mmol/L

30. 2014
• Both Sweat chloride and sweat conductivity was done in 738
cases.
• Conductivity values above 90 mmol/L had 83.3% sensitivity,
99.7% specificity, 90.9% PPV and 99.4% NPV to diagnose CF.
• The sweat conductivity test yielded a high degree of
diagnostic accuracy and it showed good agreement with
sweat chloride.

31. Nasal Potential Difference
measurement:
• In CF, lack of CFTR function leads to defective Cl secretion and Na
hyperabsorption causing dehydration of mucous secretions.
• Nasal PD measures the voltage created by Cl and Na as they move
across the nasal epithelium.

32. Nasal Potential Difference
measurement:
2 electrodes:
• Exploring electrode: placed on the floor
of the nose or under inferior turbinate,
• Reference electrode: subcutaneous
tissue of the forearm or over an area of
abraded skin.

33. Nasal Potential Difference
measurement:
• In CF, there is a more negative basal PD due to Na hyperabsorption.
• Greater change in PD (becoming less negative) occurs after application of amiloride (Na channel
inhibitor) to the nasal epithelium.
Normal CF

34. Evaluation of CFTR function by nasal potential difference of young
children with inconclusive results at CF newborn screening is a useful
diagnostic tool for CF.

35. Mutation Analysis:
• There are over 1900 different CF gene mutations associated with CF
disease.
• F508 mutation is present in 70 % of the Caucasian population.
• Other common mutations include 394delTT, R117H, G551D, etc.
• Each mutation causes same disease pathology by different mechanism.

36. Features of disease producing
mutation in a CFTR gene:
• A change in the amino acid sequence that severely affects CFTR synthesis and/or
function
• A deletion, insertion, or nonsense mutation, which introduces a premature
termination signal (stop mutation)
• Alteration to the first two or last two nucleotides of an intron splice site
• A novel amino acid sequence that is not a “normal” variant (found in at least 100
carriers within the subject’s ethnic background)

39. • Confirming the diagnosis of CF requires presence of 2 CF-disease causing
mutation.
• However, this proves to be highly specific but not very sensitive.
• This is because CF mutations vary within geographic region and human race.
• Hence, customizing mutation panels to match patient’s ethnic background
and clinical presentation can enhance the sensitivity of DNA testing in CF.
• Failure to find 2 CF mutations from a selective of extended search does not
exclude the diagnosis of CF.

41. The CFTR2 (http://www.cftr2.org) website is a useful resource designed
to provide information about specific CF mutations to patients,
researchers, and the general public
Each mutation in the database provides information about:
• Disease status (is the mutation is disease causing or not)
• Clinical characteristics (the average lung function, pancreatic status,
and Pseudomonas aeruginosa infection rates in patients).

42. CFSPIS - CF Screening Positive with Inconclusive Diagnosis
• CFTR related metabolic disorders
CF
Phenotypes:
Classic CF
Atypical /
non-classic CF
CFTR – related
disorders
CFSPID

43. Classic CF
Infants present with:
• Meconium ileus
• Rectal prolapse
• Unexplained malnutrition
As the child grows older:
• Recurrent chest infections
• Malabsorption
• Pancreatic insufficiency
• Pancreatic insufficiency is present in around 85% of classic CF
Positive sweat test and / or 2 CFTR mutation is diagnostic

44. Atypical / non-classic CF
• Also called “Equivocal CF” or “variant CF”
• Sweat testing can be normal, equivocal, or positive
• CFTR mutation analysis may reveal one, two or no mutations
• In case of 2 mutations, one is usually a “mild” mutation resulting in
partial CFTR expression and function.
• Both diagnostic labelling and medical management needs to be
tailored to the patient’s individual phenotype and requirement.

45. CFTR related disorder
• This involves subjects with a clinical entity associated with CFTR
dysfunction that does not fulfill the diagnostic criteria of CF.
• May have single organ CF like condition.
• 3 main clinical entities include:
• Congenital bilateral absence of the vas deferens
• Acute recurrent or chronic pancreatitis
• Disseminated bronchiectasis

46. CFSPID / CFTR related metabolic
syndrome
• Previously described as ”Pre-CF”
• Screening test positivity involves:
• Hyper-trypsinogenemia with 2 CFTR mutations (1 of which is not disease
causing)
• Disease causing mutations with an equivocal sweat chloride levels
• No evidence of end organ CF disease, at least on standard clinical
work-up.
• May develop the disease as age progresses.

47. Assessment of end organ effects:
Lung imaging
HRCT showing early changes of
Bronchiectasis
Paranasal sinus
CT imaging
showing polyps
Pancreatic
function testing
Fecal elastase
levels
Microbiological
culture
Typical CF pathogens
like S. aureus, P.
aeruginosa
Semen analysis
Azoospermia

48. • Primary studies (125 total) from 22 countries described abnormalities,
dysfunction, and disease progression in infancy and early childhood.
• Improved health was consistently observed in association with diagnosis
via newborn screening compared with cohorts diagnosed later by
symptomatic presentation.

49. 1977
• Younger siblings' conditions were diagnosed before 1 year of age, usually before the onset
of pulmonary disease. Older siblings' conditions were diagnosed after 1 year of age and
after the onset of pulmonary disease.
• Both sibling pairs received similar treatment and were compared at 7 years of age.
• The results suggest that, in general, early initiation of therapy is beneficial for patients with
cystic fibrosis in terms of better chest roentgenogram scores, total clinical scores, residual
lung volumes, and ratios of residual volume to total lung volume.

50. Take home points:
• Cystic fibrosis usually presents with typical symptom complex.
• Detailed family and past history is very important to diagnose CF.
• CF has different genetic mutations in different geographic regions.
• Now after knowing the symptom complex, we should have a low
threshold in diagnosing CF.
• We are fortunate to have sophisticated diagnostic tests like Macroduct
sweat chloride analysis in our hospital.
• In case of suspicion, urgent referral to a pulmonologist is essential.

51. Referrences:
• Hodson and Gedde’s book in Cystic Fibrosis.
• Kendig’s textbook of pediatric respiratory diseases
• ERS handbook of pediatric respiratory diseases
• Journal of Cystic Fibrosis
• Thorax journal
• JAMA pediatrics
• “pedpulmo” channel on www.youtube.com

52. Thank you