Assessing quality assurance for sweat chloride testing.
Variations in sweat chloride tests were analyzed.  A total of 1,806 sweat test results were analyzed for intra-assay and inter-assay variation in sweat chloride concentration and sweat weight. The mean and standard deviation of sweat chloride determinations for the negative population was 11.63 mmol/L (7.20 s.d.); for the borderline population was 50.01 mmol/L (6.27 s.d.); and for the positive population was 96.75 mmol/L (s.d. = 13.81).  The percent of sweat tests that were negative was 86.77, borderline, 3.82, and positive, 9.41.  The variation, represented as the standard deviation, between bilateral sweat chloride values on the same patient for negative results is 10.23 and for positive results is 14.60.  The average variation within a patient with regard to sweat weight is 19%. Clinical laboratory scientists can use this information in assessing their own quality assurance procedures and patient results.
Division of Clinical Laboratory Science, University of North Carolina at Chapel Hill 27599.
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D002712:Chlorides / Q000032:analysis*; D003550:Cystic Fibrosis / Q000175:diagnosis*; D006801:Humans; D011785:Quality Assurance, Health Care / Q000592:standards; D012016:Reference Values; D013542:Sweat / Q000737:chemistry