Indirect measurements of sweat electrolyte concentration in the laboratory diagnosis of cystic fibrosis

摘要

AIM—To investigate whetheranalytical methods based on the colligative physical chemicalproperties of ions or solutes in sweat are less effective than thespecific measurement of electrolytes in the diagnosis of cysticfibrosis (CF).
METHODS—A single sweat sample wascollected (Macroduct) from each of 211 infants and children, of whom 57 had CF, for the measurment of sodium, chloride, osmolality, and conductivity.
RESULTS—The ranges within which CFand non-CF individual values overlapped (equivocal ranges), were widerfor sodium and osmolality measurement than for chloride orconductivity. Neither of the latter two measurements provided adiscriminatory advantage over the other. The utilisation of broadlybased age related ranges for non-CF control subjects served to improvethe discriminatory power of all four measurements to an extent that, inthis cohort, both chloride and conductivity provided complete discrimination.
CONCLUSION—Sweat conductivity is aseffective as chloride measurement in the laboratory diagnosis of CF.