PT  - JOURNAL ARTICLE
AU  - Mary E Heeley
AU  - David A Woolf
AU  - Anthony F Heeley
TI  - Indirect measurements of sweat electrolyte concentration in the laboratory diagnosis of cystic fibrosis
AID  - 10.1136/adc.82.5.420
DP  - 2000 May 01
TA  - Archives of Disease in Childhood
PG  - 420--424
VI  - 82
IP  - 5
4099  - http://adc.bmj.com/content/82/5/420.short
4100  - http://adc.bmj.com/content/82/5/420.full
SO  - Arch Dis Child2000 May 01; 82
AB  - AIM To investigate whether analytical methods based on the colligative physical chemical properties of ions or solutes in sweat are less effective than the specific measurement of electrolytes in the diagnosis of cystic fibrosis (CF). METHODS A single sweat sample was collected (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 CF and non-CF individual values overlapped (equivocal ranges), were wider for sodium and osmolality measurement than for chloride or conductivity. Neither of the latter two measurements provided a discriminatory advantage over the other. The utilisation of broadly based age related ranges for non-CF control subjects served to improve the discriminatory power of all four measurements to an extent that, in this cohort, both chloride and conductivity provided complete discrimination. CONCLUSION Sweat conductivity is as effective as chloride measurement in the laboratory diagnosis of CF.