Diagnostic Ranges; Initial Sweat Rate - Elitech NANODUCT 1030 User Manual

Section 3: Sweat Induction and Analysis
The induction/analysis module is therefore programmed to make an average conductivity assessment by
noting the time at which the first conductivity result is displayed, allowing a time lapse of 3 minutes and
then commencing a 5-minute averaging period, after which the mean value is displayed.

Diagnostic Ranges

Normal = below 50 mmol/L*
Equivocal = 50 to 80 mmol/L*
CF = above 80 mmol/L*
*equivalent NaCl

Initial Sweat Rate

One advantage of the unique continuous-flow sensing device of the Nanoduct System is that it allows
computation of the initial sweat rate. The volume of the sensor channel from the first electrode to the
second electrode contact is precisely known, as is the collecting surface area. After the sensor is attached
to the arm, the time taken for this volume to be filled with sweat is measured by the Induction/Analysis
module.
Applying an algorithm with the fill time as the sole variable allows a display of the initial sweating rate in the
conventionally accepted units of grams of sweat per square meter of skin surface per minute. This datum is
available when the first reading is displayed on the continuous record of conductivity.
Using the data displayed in Fig 1, which show both sweat rate and conductivity
variation with time after stimulation, the Nanoduct averaged value (over period C)
was obtained (46 mmol/L).
This can be compared with the value (47 mmol/L) that would theoretically have
been obtained using a Macroduct-obtained mixed sweat yield over 30 minutes,
the standard collection time used in the clinical trial that provided the basic
results for the selection of the currently-established normal, equivocal, and
CF diagnostic ranges. It is clear that the Nanoduct results may confidently be
evaluated with reference to these ranges, for children under 16 years of age,
normal below 50 mmol/L, equivocal 50 to 80 mmol/L, and CF above 80
mmol/L (equivalent NaCl).
In non-CF adults, the normal range is frequently extended into the equivocal
levels, but never sufficiently to provide a false positive diagnosis.
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