Sweat Test
POCT Test Name
Sweat test
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Instrument Iontophoresis. Using a standardised procedure, sweat glands on the forearm or leg are stimulated to produce sodium and chloride ions with a mixture of chemical (pilocarpine) and electrical (4mA) techniques. The resultant sweat is collected carefully and returned to CHLabs with documentation, for analysis. |
Location within CDHB
CHLabs
Paediatric Outpatients Department, Chch Hospital
Tests measured
sodium- atomic absorption spectrophotometry
chloride- mercuric thiocyanate titration
Sample and volume requirements
At least 50mg, preferably 100 mg of sweat must be collected
Consumables
N/A
Controls
Laboratory QC
Reference Range
Chloride less than 40: A sweat chloride concentration less than 40 mmol/L makes cystic fibrosis unlikely, although cases have been described. The likelihood of cystic fibrosis decreases with decreasing sweat chloride levels so that a sweat chloride less than 20 mmol/L makes cystic fibrosis extremely unlikely."
Chloride 40-60: A sweat chloride concentration between 40 and 60 mmol/L is suggestive of the diagnosis of Cystic Fibrosis. Recommend CFTR mutation analysis to confirm or clarify the diagnosis.
Chloride greater than 60: A sweat chloride concentration greater than 60 mmol/L strongly supports the diagnosis of Cystic Fibrosis. Recommend CFTR mutation analysis to confirm or clarify the diagnosis
Sources of Error
Insufficient sample
Contamination of sample.
Competencies
Please click on the Competencies page.
