Units:
mmol/L
|
chloride
|
chloride
|
|
Age
|
up to 6 months
|
6 months or more
|
|
Normal
|
<= 29
|
<= 39
|
|
Intermediate
|
30 - 59
|
40 - 59
|
|
Indicative of Cystic Fibrosis
|
>= 60
|
>= 60
|
Uncertainty of Measurement: 10%
Sweat analysis is normally performed on a Thursday. Sweat guidelines recommend samples should be analysed within 72 hours of collection.
-
Chloride shows better discrimination between CF and non-CF than sodium.
-
Sweat chloride increases with age. Values >60 are occasionally seen in subjects over 10 years of age.
-
A chloride value above 160 mmol/L suggests contamination or laboratory error.
-
For sweat collected by the Gibson and Cooke method, a minimum of 75 mg of sweat is required.
97.5th centiles for sweat chloride in non-CF subjects (ref 2)
|
Age (yr)
|
Chloride
|
|
5-9
|
39.5
|
|
10-14
|
49.0
|
|
15-19
|
53.3
|
|
20+
|
59.6
|
References
1. Sweat testing: Sample Collection and Quantitative Chloride Analysis; Approved Guideline-Third Edition. CLSI document C34-A3.: Clinical and Laboratory Standards Institute, 2009.
2. Mishra A, Greaves R, Smith K, Carlin JB, Wootton A, Stirling R, et al. Diagnosis of cystic fibrosis by sweat testing: age-specific reference intervals. The Journal of pediatrics 2008;153(6):758-63.
3. Guidelines for the Performance of the Sweat Test for the Investigation of Cystic Fibrosis in the UK, 2nd version, March 2014.
4. Australasian Guideline (2nd Edition): an Annex to the CLSI and UK Guidelines for the Performance of the Sweat Test for the Diagnosis of Cystic Fibrosis, Clin Biochem Rev 38 (3) 2017