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Sweat Chloride Test
MessageThe sweat test measures the amount of chloride (a component of salt) in the sweat. There are no needles involved in this test. In the first part of the test, a colorless, odorless chemical (pilocarpine) and a little electrical stimulation is applied to a small area of the arm or leg to encourage the sweat glands to produce sweat. A person may feel tingling in the area, or a feeling of warmth. This part of the test lasts about five minutes.
The sweat is then collected on a piece of gauze. This step lasts for 30 minutes. The collected sweat is then sent to the laboratory to measure how much chloride is in the sweat. The sweat test usually takes about an hour, but it may take longer.
Test Code
Sweat Chloride Study
Alias/See Also
Sweat Chloride Study
CPT Codes
89230x2, 82438x2
Includes
Sweat Chloride Site
Sweat Chloride Collection (weight) - mg
Sweat Chloride Study (concentration) – mmol/L
Sweat Chloride Collection (weight) - mg
Sweat Chloride Study (concentration) – mmol/L
Preferred Specimen
Sweat
Patient Preparation
Patient must be clinically stable, well hydrated, free from acute illness and not on mineralcorticoids. No lotions should be applied to testing areas. Testing is performed on both arms or both legs.
Minimum Volume
75 mg
Instructions
Patients should not have a fever, any diarrhea or any vomiting in the past 24-48 hours. Sweat production is affected by these symptoms.
Patients should have normal diet and water intake, necessary for adequate sweat collection.
If IV, IV will need to be turned off for an hour prior to collection and during collection process.
If patient is receiving oxygen, will need to be turned off during the stimulation process.
If patient has any medical equipment attached, the medical equipment will need to be turned off during the stimulation process.
Patient must not have any rashes, hives, burns, psoriasis or large wounds/sores on the testing areas (the arms or legs).
Patients should have normal diet and water intake, necessary for adequate sweat collection.
If IV, IV will need to be turned off for an hour prior to collection and during collection process.
If patient is receiving oxygen, will need to be turned off during the stimulation process.
If patient has any medical equipment attached, the medical equipment will need to be turned off during the stimulation process.
Patient must not have any rashes, hives, burns, psoriasis or large wounds/sores on the testing areas (the arms or legs).
Transport Container
None, collected by laboratory staff
Specimen Stability
Samples are stable until transported to the laboratory usually within 5-10 minutes.
Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)
< 75 mg sweat
Methodology
Iontophoresis for collection
Chloridometer for testingFDA Status
FDA Approved
Setup Schedule
M, W, F (2-3 collection per day)
Report Available
Same day
Limitations
If < 75 mg of sweat are collected on both collections (arms or legs), testing for chloride concentration cannot proceed. If one collection is above 75 mg, that collection will be tested and reported per CFF guidelines.
Reference Range
<30 mmol/L
Newborns with a positive screen (NBS): CF unlikely; may repeat this test if indicated by family history or CF symptoms.
Other populations: CF unlikely. Rarely individuals may be considered to have CF if alternatives are excluded and other confirmatory tests such as genetic and physiologic testing support CF
30-59 mmol/L
All populations: Individuals presenting with a positive newborn screen, symptoms of CF or a positive family history on two separate occasions may have CF. They should be considered for extended genetic analysis and/or CFTR physiologic testing to rule in or rule out CF and to designate CFTR related metabolic syndrome
≥ 60 mmol/L
All populations: Indicative of CF for individuals presenting with a positive newborn screen, clinical features consistent with CF, or a positive family history
References: Farrell PM et al 2017
Newborns with a positive screen (NBS): CF unlikely; may repeat this test if indicated by family history or CF symptoms.
Other populations: CF unlikely. Rarely individuals may be considered to have CF if alternatives are excluded and other confirmatory tests such as genetic and physiologic testing support CF
30-59 mmol/L
All populations: Individuals presenting with a positive newborn screen, symptoms of CF or a positive family history on two separate occasions may have CF. They should be considered for extended genetic analysis and/or CFTR physiologic testing to rule in or rule out CF and to designate CFTR related metabolic syndrome
≥ 60 mmol/L
All populations: Indicative of CF for individuals presenting with a positive newborn screen, clinical features consistent with CF, or a positive family history
References: Farrell PM et al 2017
Clinical Significance
Performing Laboratory
BUMC-Tucson Main Lab
