Inconsistencies in sweat testing in UK laboratories.
BACKGROUND
Sweat testing procedures are perceived to vary widely.


OBJECTIVE
To evaluate variability in sweat collection, analysis, and interpretation.


METHODS
Questionnaire responses from 30 self selected centres: 15 paediatric centres, and 15 district general hospitals.


RESULTS
Centres carried out 30-400 tests per year (median 100), with a diagnostic rate of 1:5-152 (median 1:30). Staff performed 5-268 tests per year. Minimum test age varied from 24 hours to four months. All stimulated sweating by pilocarpine iontophoresis using varying currents and times. Twenty six had observed urticaria or skin reddening, and nine blistering or burns. Sweat was collected for 10-60 minutes onto filter paper or into Macroduct coils. Between 2% and 25% of tests were considered insufficient. Twenty eight measured sodium, 24 chloride, and one osmolality and conductivity. Fifteen used literature and five in house reference ranges. Eleven would not test severely eczematous children.


CONCLUSIONS
Local audit is required to improve performance, as well as a national guideline to standardise collection, and external quality assessment to provide analytical feedback.
Kirk
J M
JM
Department of Paediatric Biochemistry, Royal Hospital for Sick Children, Edinburgh, Scotland, UK. Jean.M.Kirk@btinternet.com
D000367:Age Factors; D019411:Clinical Laboratory Techniques / Q000592:standards* / Q000706:statistics & numerical data; D003550:Cystic Fibrosis / Q000175:diagnosis*; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007755:Laboratories, Hospital / Q000592:standards* / Q000706:statistics & numerical data; D012016:Reference Values; D013542:Sweat / Q000737:chemistry*; D006113:United Kingdom