The sweat test: effect of elution time on chloride and sodium concentrations.
BACKGROUND
The National Committee for Clinical Laboratory Standards guidelines and Guidelines for the Performance of the Sweat Test for the Diagnosis of Cystic Fibrosis in the United Kingdom recommend that sweat be eluted from filter paper for a minimum of 40 min. In the absence of published data, this recommendation is based on expert opinion. We therefore investigated the effect of elution time on chloride and sodium concentrations.


METHODS
The effect of elution time (up to three hours) on chloride and sodium concentrations was studied as recommended for measurement of quality control samples using external quality assessment solutions.


RESULTS
There were no significant differences in eluted chloride and sodium concentrations with time of elution up to 3 h.


CONCLUSIONS
Elution time within 3 h had no effect on chloride and sodium concentrations when eluted from filter paper.
Gilbert
Christopher J
CJ
Clinical Chemistry, New Cross Hospital, Wolverhampton, West Midlands WV10 0PQ, UK.
Griffiths
Melanie J
MJ
Holland
Martin R
MR
Gama
Rousseau
R
D002712:Chlorides / Q000032:analysis*; D003550:Cystic Fibrosis / Q000175:diagnosis; D017408:Guidelines as Topic; D006801:Humans; D011786:Quality Control; D012964:Sodium / Q000032:analysis*; D013542:Sweat / Q000737:chemistry*
D002712:Chlorides; D012964:Sodium