Evaluation of the intestinal current measurement method as a diagnostic test for cystic fibrosis

Background The sweat test and nasal potential difference measurement are now established tools in the diagnostic work up of cystic fibrosis (CF). Intestinal current measurement (ICM) is under consideration as an aid in the diagnosis of CF especially in young children. The aim of this study is to evaluate the diagnostic reliability of ICM. Methods Rectal biopsies were obtained from three groups: CF patients, controls, and patients who were suspected for CF. ICMs were performed by mounting the rectal biopsy in an Ussing chamber and sequentially adding secretagogues while recording current changes. Results Twenty-one CF patients (aged 3.0 +/- 3.8 years) and 16 controls (aged 15.6 +/- 15.1 years) were examined and have remarkably different results (presented as mu A/cm2): carbachol 16.3 +/- 6.9, histamine 13.2 +/- 8.9, and cAMP/forskolin 4.8 +/- 4.0 for control group and carbachol 1.5 +/- 5.3 (P<0.0001), histamine 1.5 +/- 3.1 (P<0.0001), and cAMP/forskolin 0.36 +/- 0.67 (P<0.0001) for the CF group. Our suggested reference values are: +5.40, +3.52, +2.19 for carbachol, histamine, and cAMP/forskolin, respectively. The combination parameter (the arithmetic sum of carbachol, histamine, and cAMP/forskolin) of +7.19 differentiates normal from abnormal (ROC curve analysis, area under the curve=1.00, both sensitivity and specificity are 100%). This statistical model was applied to 71 patients suspected for CF and revealed that 66 patients had normal ICM results (combination >7.19) and five patients had abnormal ICM results (combination <7.19). Conclusion We have shown that ICM tests may be useful to differentiate between patients suspected to have CF. These results require confirmation so that ICM may be included in diagnostic algorithms. Pediatr Pulmonol. 2013; 48:229235. (c) 2012 Wiley Periodicals, Inc.