Reliability of sweat-testing by the Macroduct collection method combined with conductivity analysis in comparison with the classic Gibson and Cooke technique

Abstract

Sweat-testing by the MCS has acceptable sensitivity and specificity when performed by trained CF sweat-testing technicians. Additional studies will be required to find out if these results can be confirmed in small clinics and hospitals where testing is done infrequently. Wherever the MCS is used all positive or borderline results should be confirmed by the GCT at a reference Cystic Fibrosis Center.

Sweat conductivity for the diagnosis of cystic fibrosis

“…In our experience, the immediate availability of results was both clinically useful for planning further investigation and management, and much appreciated by subjects and their parents. Our success rates for conductivity measurement, and laboratory chloride measurement on the same sample, are comparable with those obtained in larger and more specialist units [1,2], but demonstrate that repeat sweat collection is necessary in a significant number of patients if sweat chloride is deemed an essential analyte. The relatively small number of subjects in our study, particularly those with cystic fibrosis, means that our results lack the statistical power to indicate that conductivity measurement alone can replace laboratory chloride estimation for the diagnosis of cystic fibrosis.…”

“…They and others [2] have suggested that further experience of its use is reported across a range of clinical settings before considering it as a definitive diagnostic test. Furthermore, evidencebased guidelines, produced by a multidisciplinary working group supported by the Cystic Fibrosis Trust, and appraised by the Royal College of Paediatrics and Child Health in the United Kingdom, have emphasised the importance of continued measurement of sweat chloride as an essential analyte until the relative merits of conductivity have been established [3].…”

Nanoduct® sweat testing for rapid diagnosis in newborns, infants and children with cystic fibrosis

“…The determination of conductivity in sweat as a test for approximation to electrolytes in a non selective manner has been shown to be as effective as the quantitative determination of sweat chloride or sodium concentrations. Several studies have demonstrated, that conductivity levels have an equal potential to discriminate diagnostically between CF and non-CF subjects [1,13,14,19]. Compared to the classic Gibson and Cook procedure, testing for conductivity is easier to perform and requires a smaller sample of sweat.…”

“…In the past, several attempts were made to improve the methods of stimulation, collection and analysis of sweat samples [4,16,19,20]. The determination of conductivity in sweat as a test for approximation to electrolytes in a non selective manner has been shown to be as effective as the quantitative determination of sweat chloride or sodium concentrations.…”

Conductivity determined by a new sweat analyzer compared with chloride concentrations for the diagnosis of cystic fibrosis

“…7 This method is well established but time-consuming and open to many sources of error. It has been shown to be reliable even for infants in laboratories with trained, experienced and skilled technicians, 8,9 but in our hands, difficulties arose in newborn infants during the first month of life because at least 75 mg of sweat should be obtained on gauze or filter paper in 30 minutes for an accurate result. 10 In the past, there have been many improvements in the method for sweat collection.…”