A new method of sweat testing: the CF Quantum®sweat test.

BACKGROUND Conventional methods of sweat testing are time consuming and have many steps that can and do lead to errors. This study compares conventional sweat testing to a new quantitative method, the CF Quantum® (CFQT) sweat test. This study tests the diagnostic accuracy and analytic validity of the CFQT. METHODS Previously diagnosed CF patients and patients who required a sweat test for clinical indications were invited to have the CFQT test performed. Both conventional sweat testing and the CFQT were performed bilaterally on the same day. Pairs of data from each test are plotted as a correlation graph and Bland-Altman plot. Sensitivity and specificity were calculated as well as the means and coefficient of variation by test and by extremity. After completing the study, subjects or their parents were asked for their preference of the CFQT and conventional sweat testing. RESULTS The correlation coefficient between the CFQT and conventional sweat testing was 0.98 (95% confidence interval: 0.97-0.99). The sensitivity and specificity of the CFQT in diagnosing CF was 100% (95% confidence interval: 94-100%) and 96% (95% confidence interval: 89-99%), respectively. In one center in this three center multicenter study, there were higher sweat chloride values in patients with CF and also more tests that were invalid due to discrepant values between the two extremities. The percentage of invalid tests was higher in the CFQT method (16.5%) compared to conventional sweat testing (3.8%) (p < 0.001). In the post-test questionnaire, 88% of subjects/parents preferred the CFQT test. CONCLUSIONS The CFQT is a fast and simple method of quantitative sweat chloride determination. This technology requires further refinement to improve the analytic accuracy at higher sweat chloride values and to decrease the number of invalid tests.

[1]  D. Schidlow,et al.  Evaluation of a Paper-patch Test for Sweat Chloride Determination , 1984, Clinical pediatrics.

[2]  R. Bowman,et al.  An instrument and method for automatic, rapid, accurate, and sensitive titration of chloride in biologic samples. , 1958, The Journal of laboratory and clinical medicine.

[3]  M. Rosenfeld,et al.  Cystic Fibrosis Foundation practice guidelines for the management of infants with cystic fibrosis transmembrane conductance regulator-related metabolic syndrome during the first two years of life and beyond. , 2009, The Journal of pediatrics.

[4]  Vicky A Legrys,et al.  Guidelines for diagnosis of cystic fibrosis in newborns through older adults: Cystic Fibrosis Foundation consensus report. , 2008, The Journal of pediatrics.

[5]  R. Parad,et al.  Sweat testing infants detected by cystic fibrosis newborn screening. , 2005, The Journal of pediatrics.

[6]  K B Hammond,et al.  Clinical evaluation of the macroduct sweat collection system and conductivity analyzer in the diagnosis of cystic fibrosis. , 1994, The Journal of pediatrics.

[7]  W. M. Layton,et al.  A polarographic micromethod for the determination of blood chloride. , 1949, The Journal of biological chemistry.

[8]  V. Legrys,et al.  Testing diagnostic tests: why size matters. , 2005, The Journal of pediatrics.

[9]  D. Altman,et al.  Measuring agreement in method comparison studies , 1999, Statistical methods in medical research.

[10]  D. Rennie,et al.  The STARD statement for reporting studies of diagnostic accuracy: explanation and elaboration. , 2003, Annals of internal medicine.

[11]  V. Legrys,et al.  Incidence and implications of false‐negative sweat test reports in patients with cystic fibrosis , 1988, Pediatric pulmonology.

[12]  D. Cole,et al.  Use of a new sample-collection device (Macroduct) in anion analysis of human sweat. , 1986, Clinical chemistry.

[13]  O. Schales,et al.  A SIMPLE AND ACCURATE METHOD FOR THE DETERMINATION OF CHLORIDE IN BIOLOGICAL FLUIDS , 1941 .

[14]  R E COOKE,et al.  A test for concentration of electrolytes in sweat in cystic fibrosis of the pancreas utilizing pilocarpine by iontophoresis. , 1959, Pediatrics.

[15]  S. McColley,et al.  The need for quality improvement in sweat testing infants after newborn screening for cystic fibrosis. , 2010, The Journal of pediatrics.

[16]  B. Kerem,et al.  Consensus on the Use and Interpretation of Cystic Fibrosis Mutation Analysis in Clinical Practice , 2022 .

[17]  P. Farrell,et al.  Parents' Knowledge of Neonatal Screening and Response to False‐Positive Cystic Fibrosis Testing , 1992, Journal of developmental and behavioral pediatrics : JDBP.

[18]  C. Castellani,et al.  CFTR2: How will it help care? , 2013, Paediatric respiratory reviews.