Sweat Test
Clinical Background:
The sweat test generates a sweat sample that is used for the diagnosis and confirmation of Cystic Fibrosis (CF). CF is the major cause of raised sweat chloride concentration with the main different...
The sweat test generates a sweat sample that is used for the diagnosis and confirmation of Cystic Fibrosis (CF). CF is the major cause of raised sweat chloride concentration with the main differential diagnosis being anorexia nervosa.Indications for a sweat test include: phenotype suggestive of CF (e.g. multiple chest infections of unknown cause/growth faltering of unknown cause/meconium ileus, family history of CF, a positive or equivocal newborn screening test, suspicion of an atypical CF phenotype
Test Details
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Discipline:
Biochemistry
Biochemistry
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Specimen Container Paediatric:
Sweat collected with special equipment
Sweat collected with special equipment
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Minimum Volume Adult:
18 µL sweat
18 µL sweat
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Minimum Volume Paediatric:
18 µL sweat
18 µL sweat
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Special Requirement:
Infants should be greater than 3kg weight. Can be attempted in term infants after 7 d of age, but usually not done until after 3 weeks of age.
Infants should be greater than 3kg weight. Can be attempted in term infants after 7 d of age, but usually not done until after 3 weeks of age.
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Transport Requirements:
Ambient
Ambient
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Interpretation:
Contra-indications for testing: Dehydration, oedema, systemic illness, systemic corticosteroid therapy, eczema affecting potential stimulation sites. Subjects receiving oxygen by an open delivery s...
Read MoreContra-indications for testing: Dehydration, oedema, systemic illness, systemic corticosteroid therapy, eczema affecting potential stimulation sites. Subjects receiving oxygen by an open delivery system. Reference intervals are validated in the paediatric population and may not be directly applicable to adults. Sweat chloride levels do not directly correlate with CF clinical phenotype.
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Reference Ranges:
National Guidelines for sweat test interpretation: A sweat chloride concentration of greater than 60 mmol/L supports the diagnosis of CF. An intermediate chloride concentration of 40-60 mmol/L is s...
Read MoreNational Guidelines for sweat test interpretation: A sweat chloride concentration of greater than 60 mmol/L supports the diagnosis of CF. An intermediate chloride concentration of 40-60 mmol/L is suggestive but not diagnostic. A sweat chloride of less than 40 mmol/L is normal and there is low probability of CF. If the patient is under 6 months of age, 30-60mmol/L is an intermediate result and less than 30mmol/L makes CF unlikely.
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Routine Email:
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Specialist Contact Name:
Duty Biochemist
Duty Biochemist
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Specialist Telephone:
0191 282 4025
0191 282 4025