Abstract
BackgroundThe classic sweat test (CST) is the golden standard for cystic fibrosis (CF) diagnosis. Then, our aim was compare the production and volume of sweat, and side effects caused by pulsed direct current (PDC) and constant direct current (CDC). To determine the optimal stimulation time (ST) for the sweat collection. To verify the PDC as CF diagnosis option.MethodsProspective study with cross-sectional experimental intervention. Experiment 1 (right arm): PDC and CDC. ST at 10 min and sweat collected at 30 min. Currents of 0.5; 0.75; 1.0 and 1.5 mA and frequencies of 0, 200, 1,000 and 5,000 Hz applied. Experiment 2 (left arm): current of 1.0 mA, ST at 5 and 10 min and sweat collected at 15 and 30 min with frequencies of 0; 200; 1,000 and 5,000 Hz applied Experiments 1 and 2 were performed with current density (CD) from 0.07 to 0.21 mA/cm2. Experiment 3: PDC was used in typical CF patients with two CFTR mutations screened and or with CF diagnosis by rectal biopsy and patients with atypical CF.Results48 subjects (79.16% female) with average of 29.54 ± 8.87 years old were enrolled. There was no statistical difference between the interaction of frequency and current in the sweat weight (p = 0.7488). Individually, positive association was achieved between weight sweat and stimulation frequency (p = 0.0088); and current (p = 0.0025). The sweat production was higher for 10 min of stimulation (p = 0.0023). The sweat collection was better for 30 min (p = 0.0019). The skin impedance was not influenced by ST and sweat collection (p > 0.05). The current frequency was inversely associated with the skin impedance (p < 0.0001). The skin temperature measured before stimulation was higher than after (p < 0.0001). In Experiment 3 (29 subjects) the PDC showed better kappa index compared to CDC (0.9218 versus 0.5205, respectively).ConclusionsThe performance of the CST with CDC and PDC with CD of 0.14 to 0.21 mA/cm2 showed efficacy in steps of stimulation and collection of sweat, without side effects. The optimal stimulation time and sweat collection were, respectively, 10 and 30 min.Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2466-14-198) contains supplementary material, which is available to authorized users.
Highlights
The classic sweat test (CST) is the golden standard for cystic fibrosis (CF) diagnosis
Experiment 1 – testing intensity and frequency of the current for sweat test There was no statistical difference between the interaction of frequency and current for the sweat weight (p = 0.7488) (Table 2, Figure 1)
CST is considered the golden standard for the CF diagnosis [3,4,6,23,24,25], studies have reported difficulties in performing the test, especially for sweat collection and electrolyte measurement [26,27,28]
Summary
The classic sweat test (CST) is the golden standard for cystic fibrosis (CF) diagnosis. Gibson and Cooke [2] described a method of cholinergic stimulation with pilocarpine iontophoresis on the skin to facilitate the dosage and stimulation of the sweat electrolytes. This method is known as the classic sweat test (CST), and still is considered the golden standard for CF diagnosis [3,4]. In the sweat gland ducts, chloride ions (Cl-) are reabsorbed by the CFTR (cystic fibrosis transmembrane regulator) [5]. CF patients show in the distal ducts of sweat gland, absence or defect of CFTR protein, and reduction of Cl- reabsorption [8,9]
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