Elitech NANODUCT 1030, Руководство пользователя

Страница: 62 / 71

62
While the iontophoretic transport of pilocarpine into the glands has remained the universally preferred
method of sweat stimulation to this day, the need for a simpler method of collection and analysis spawned
the development of alternative procedures during the late 60’s and early 70’s. Principally among these
were the cup-collection systems, which used electrical conductivity for analysis, and the direct skin chloride
electrode system.
These methods were highly innovative, procedurally simpler than the Gibson and Cooke method, and were
initially commercially successful. They nevertheless failed in their objective to eliminate false diagnostic
results. The adoption of these new procedures on a wide scale exacerbated the problem, evoking a storm
of criticism in the professional literature, with calls for a return to the original pad-absorption which was now
regarded as the “reference method.”
2, 3, 4
In fact, CF referral centers in the United States, operating under
accreditation of the Cystic Fibrosis Foundation were forbidden to use any sweat test method other than the
QPIT.
These early attempts to simplify the sweat test failed for two principal reasons: (1) error intrinsic to the
method of collection and beyond the control of the operator, or (2) extreme susceptibility to variations in
operator technique. The direct skin chloride electrode, though offering unrivaled simplicity, was very prone
to operator variability in manual skill, and gave poor results due mainly to great difficulties experienced in
the control of evaporation error.
The cup collection method was examined for potential intrinsic error by Webster
5
who found that the
phenomenon of condensate formation on the walls of the plastic cups was the principal cause of the
trouble. His quantitative measurements of the degree to which this occurred in unheated plastic cups
showed that the error was always significant and very often reached proportions sufficient to produce false
positive results. The error was avoided by using a metal collector cup that was maintained at above skin
temperature throughout sweat collection, condensation was prevented, and the error disappeared.
In 1978, Wescor (now ELITechGroup)introduced the Model 3500 Webster Sweat Collection System that
employed an electrically-heated metallic collector cup.
6
It was the first “simplified” sweat collection system
worthy of comparison with the Gibson and Cooke method, it enjoyed considerable success, and was free
from any criticism by users and related professionals. It was however burdened by a problem common to
all cup-collection systems, that is, the need to “harvest” the sweat accumulated beneath the cup during
collection.
Wescor’s determined commitment to resolve this problem eventually led to the invention of the
MACRODUCT
®
Sweat Collector.
7
This innovation completely supplanted the heated cup, while retaining its
advantages by the use of a collector that anaerobically collected sweat by using the hydraulic pressure of
the sweat glands to pump the secretion directly from the ducts into a fine-bore capillary tube. This system
has been very successfully employed both in the US and internationally since 1983.
Vested in ELITechGroup’s scientific and engineering staff is a combination of many years of experience in
laboratory sweat testing and in the development of modern electronic instrumentation. The ELITechGroup
aim in the field of sweat testing has always been to provide quality instrumentation to meet a number of
criteria.
1. Elimination of all intrinsic sources of error concomitant to previous collection methods.
2. Ensuring impeccable accuracy in the diagnostic result by reducing human error potential to the lowest
possible level.
3. Maximization of patient safety and comfort.
4. Maximization of operator convenience within the strictures imposed by objectives 1, 2 and 3.
These objectives have led to considerable innovative improvements in all aspects of sweat testing,
iontophoretic safety measures, collection methods and also in the analytical phase of the test. With the
introduction of the Model 3600 Macroduct Sweat Collection System in 1983, all of the comprehensive
objectives had been accomplished. Paramount among the system’s several unique features was the
innovative Macroduct disposable sweat collector.
Appendix H: Supplemental Information