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.

Conclusion: Elution time within 3 h had no effect on chloride and sodium concentrations when eluted from filter paper.