Aalbers BL, et al. - Researchers examined 86 patients with 5T (5T polymorphism is a CFTR mutation), to assess whether nasal potential difference (NPD) and sweat testing correlate with symptoms and Cystic Fibrosis (CF) diagnosis in these subjects. Participants had NPD measurement done, and included 6 homozygous (5T/5T), 41 with a PI-CF causing mutation in trans (5T/PI-CF), 11 with a PS-CF causing mutation in trans (5T/PS-CF) and 28 without a recognized mutation in trans (5T/?). Findings revealed that clinical status varied considerably among 5T patients. Stability or improvement over time was seen in all patients with 5T/PS CF, all patients with both normal NPD and sweat test, and most patients with TG11. For the evaluation of high risk for developing CF or CFTR-related disease and whether specific follow up in a CF center is needed, the NPD measurement and TGm (number of TG repeats in intron 8) status were shown to be helpful.