Mari L DeMarco1, Dennis J Dietzen2, Sarah M Brown2. 1. Department of Pathology and Laboratory Medicine, St. Paul's Hospital, University of British Columbia, Vancouver, Canada. Electronic address: mdmrco@mail.ubc.ca. 2. Department of Pathology and Immunology, Washington University School of Medicine, St Louis, MO, USA; Department of Pediatrics, Washington University School of Medicine, St Louis, MO, USA.
Abstract
OBJECTIVES: Sweat chloride testing is the gold standard for diagnosis of cystic fibrosis (CF). Our objectives were to: 1) describe variables that determine sweat rate; 2) determine the analytic and diagnostic capacity of sweat chloride analysis across the range of observed sweat rates; and 3) determine the biologic variability of sweat chloride concentration. METHODS: A retrospective analysis was performed using data from all sweat chloride tests performed at St. Louis Children's Hospital over a 21-month period. RESULTS: A total of 1397 sweat chloride tests (1155 sufficient [≥75 mg], 242 insufficient [<75 mg]), were performed on 904 individuals. The sweat weight collected from forearms was statistically greater than that collected from legs. There was a negligible correlation between sweat weight and chloride concentration (r=-0.06). The mean individual biologic CV calculated from individuals with two or more sweat collections ≥75 mg was 13.1% (95% CI: 11.3-14.9%; range 0-88%) yielding a reference change value of 36%. Using 60 mmol/L as the diagnostic chloride cutoff, 100% of CF cases were detected whether a minimum sweat weight of 75, 40, or 20 mg was required. CONCLUSIONS: 1) Collection of sweat from forearms is preferable to upper legs, particularly in very young infants; 2) sweat chloride concentrations are not highly dependent upon sweat rate; 3) a change in sweat chloride concentration exceeding 36% may be considered a clinically significant response to cystic fibrosis transmembrane receptor targeted therapy, and 4) sweat collections of less than 75 mg provide clinically accurate information.
OBJECTIVES: Sweat chloride testing is the gold standard for diagnosis of cystic fibrosis (CF). Our objectives were to: 1) describe variables that determine sweat rate; 2) determine the analytic and diagnostic capacity of sweat chloride analysis across the range of observed sweat rates; and 3) determine the biologic variability of sweat chloride concentration. METHODS: A retrospective analysis was performed using data from all sweat chloride tests performed at St. Louis Children's Hospital over a 21-month period. RESULTS: A total of 1397 sweat chloride tests (1155 sufficient [≥75 mg], 242 insufficient [<75 mg]), were performed on 904 individuals. The sweat weight collected from forearms was statistically greater than that collected from legs. There was a negligible correlation between sweat weight and chloride concentration (r=-0.06). The mean individual biologic CV calculated from individuals with two or more sweat collections ≥75 mg was 13.1% (95% CI: 11.3-14.9%; range 0-88%) yielding a reference change value of 36%. Using 60 mmol/L as the diagnostic chloride cutoff, 100% of CF cases were detected whether a minimum sweat weight of 75, 40, or 20 mg was required. CONCLUSIONS: 1) Collection of sweat from forearms is preferable to upper legs, particularly in very young infants; 2) sweat chloride concentrations are not highly dependent upon sweat rate; 3) a change in sweat chloride concentration exceeding 36% may be considered a clinically significant response to cystic fibrosis transmembrane receptor targeted therapy, and 4) sweat collections of less than 75 mg provide clinically accurate information.
Authors: Joseph M Collaco; Scott M Blackman; Karen S Raraigh; Harriet Corvol; Johanna M Rommens; Rhonda G Pace; Pierre-Yves Boelle; John McGready; Patrick R Sosnay; Lisa J Strug; Michael R Knowles; Garry R Cutting Journal: Am J Respir Crit Care Med Date: 2016-12-01 Impact factor: 21.405
Authors: A Tosco; F De Gregorio; S Esposito; D De Stefano; I Sana; E Ferrari; A Sepe; L Salvadori; P Buonpensiero; A Di Pasqua; R Grassia; C A Leone; S Guido; G De Rosa; S Lusa; G Bona; G Stoll; M C Maiuri; A Mehta; G Kroemer; L Maiuri; V Raia Journal: Cell Death Differ Date: 2016-04-01 Impact factor: 15.828
Authors: Ana E Fernández-Lorenzo; Ana Moreno-Álvarez; Cristóbal Colon-Mejeras; Francisco Barros-Angueira; Alfonso Solar-Boga; Josep Sirvent-Gómez; María L Couce; Rosaura Leis Journal: Medicine (Baltimore) Date: 2018-07 Impact factor: 1.889