Diagnosis of cystic fibrosis by sweat testing: age-specific reference intervals.
OBJECTIVE
To develop reference intervals (RIs) for sweat chloride and sodium in healthy children, adolescents, and adults.


METHODS
Healthy, unrelated subjects aged from 5 to >50 years and subjects who were pancreatic insufficient with cystic fibrosis (CF) were recruited. Sweat collection was performed on all subjects with the Wescor Macroduct system. Sweat electrolytes were analyzed with direct ion selective electrodes. DeltaF508 mutation analysis was performed on the healthy subjects >/=15 years old.


RESULTS
A total of 282 healthy and 40 subjects with CF were included for analysis. There was no overlap of sweat chloride between the group with CF and the group without CF, but there was some overlap of sweat sodium. Sweat chloride increased with age, with the rate of increase slowing progressively to zero after the age of 19 years. The estimated median (95% RI) for sweat chloride were: 5 to 9 years, 13 mmol/L (1-39 mmol/L); 10 to 14 years, 18mmol/L (3-47 mmol/L); 15 to 19 years, 20 mmol/L (3-51mmol/L); and 20+ years 23 mmol/L (5-56mmol/L).


CONCLUSIONS
We have successfully developed the age-related RI for sweat electrolytes, which will be useful for clinicians interpreting sweat test results from children, adolescents, and adults.
Mishra
Avantika
A
Department of Biochemical Genetics, VCGS Pathology, The Royal Children's Hospital, Parkville, Victoria, Australia.
Greaves
Ronda
R
Smith
Katherine
K
Carlin
John B
JB
Wootton
Andrew
A
Stirling
Rob
R
Massie
John
J
D000293:Adolescent; D000328:Adult; D000368:Aged; D000375:Aging / Q000378:metabolism*; D002648:Child; D002675:Child, Preschool; D002712:Chlorides / Q000378:metabolism*; D015331:Cohort Studies; D003550:Cystic Fibrosis / Q000175:diagnosis* / Q000235:genetics / Q000378:metabolism*; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000235:genetics* / Q000302:isolation & purification; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009154:Mutation; D012016:Reference Values; D012964:Sodium / Q000378:metabolism*; D013542:Sweat / Q000737:chemistry*; D055815:Young Adult
D002712:Chlorides; C093349:cystic fibrosis transmembrane conductance regulator delta F508; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D012964:Sodium