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Chloride, Quantitative Sweat by Iontophoresis

Mnemonic:    [Sweat Cl]
Name:    Chloride, Quantitative Sweat by Iontophoresis
Specimen:    Sweat sample collected by special iontophoretic procedure.
Reference Range:    Normal all ages: 1 - 29 mEq/L
Note:    Interpretation for Sweat Chloride:
Sweat chloride results should always be evaluated in light of the patientís clinical course.
Range Chloride (mEq/L)
Normal Range <30
Indeterminate Range 30-60
Consistent w/CF >60

The test results should be consistent with the clinical picture; no single laboratory result is sufficient to establish or rule out the diagnosis of CF. The criteria for the diagnosis of CF include: the presence of one or more characteristic phenotypic features, or a history of CF in a sibling, or a positive newborn screening test result; and an increased sweat chloride concentration by pilocarpine iontopherisis on two or more occasions, or identification of two CF mutations or demonstration of abnormal nasal epithelial ion transport. Two percent of patients with documented CF have sweat chlorides less than or equal to 60mEq/L. Therefore, a normal sweat chloride value cannot be used as the sole criterion for exclusion of a CF diagnosis.
Please note that the indeterminate range was updated to meet the current CF guidelines that no longer use patient age as a factor in assessing Indeterminate (formerly Borderline) status.
Method: Wescore Macroduct, Mercuric Chloride Titration

Sweat Test Information for Patients