TECNICAS CIENTIFICAS PARA LABORATORIO S.A. T620 Manuale Utente
Although several techniques have been created for the collection and measurement of sweat
electrolytes, the most reliable test is based on the pilocarpine iontophoresis technique
described by Gibson & Cooke in 1959, which is still considered to be the gold standard for
CF diagnosis specially in babies.
However, this is a complex combination of techniques that requires weigh sweat using an
analytical scale, elution and undergo biochemical analysis of electrolytes. According to this
method, it is necessary to collect at least 70 mg of sweat.
In order to make the test simpler, many labs have been using alternative methods. One of
these methods includes the use of the device Macroduct® – a sweat collection system,
through which sweat is collected into a plastic coil after stimulation by pilocarpine
iontophoresis. Weighting is thus eliminated. The sweat can be taken from the coil and its
ionic composition can be later analyzed using the usual biochemical techniques, or it may be
immediately placed in the conductivity analyzer – Sweat- Chek – Wescor, which will quickly
provide the equivalent values of sweat sodium chloride (NaCl) in mmol/L.
Because of methodological problems , confirmation or rejection of the diagnosis of CF should
only be based on the results of quantitative pilocarpine iontophoresis sweat chloride
described in the specific guidelines. Those guidelines consider not acceptable for CF
diagnostic the direct reading in situ test using Orion ISE or older electrical conductivity
measurements, or measurements or osmolality or sodium. Conductivity instruments
designed specifically for use with microbore tubing collector was approved by CFF as
screening method but only for use outside accredited Cystic Fibrosis Care Centers.
In 2010 Tecil introduced ISEsweat®, a new method for direct sweat Chloride measurement
who eliminates all intrinsic sources of error associated to collection methods and with
microISE specifically designed for microsamples. ISEsweat gives the concentration of sweat
chloride independently of the sample quantity, that’s why there is no need to measure the
amount of sweat collected.
A multicentrical clinical trial made in 113 subjects and presented at the European Cystic
Fibrosis Society concluded that ISEsweat is a valid and safety new device for sweat chloride
concentration measurement. The results of this first clinical assay are very encouraging and
warrant further research with larger samples of patients, to confirm that the ISEsweat can
become a useful tool for the diagnosis of CF and even prove to be a reliable and more
convenient alternative method compared to the reference sweat test as approved by current
guidelines.