Nasal potential difference in young children is feasible - Report from a national referral center

Background: –Nasal Potential Difference (NPD) is an established diagnostic tool for CF. However, standardized values for very young patients are lacking. Aim: – To evaluate the feasibility of performing NPD testing in young children. Methods: – We modified the standard NPD protocol for young children by shortening the infusion time per solution to 2 min. No sedation was required. Results: – Fifty-five children aged 6 days to 3 years were enrolled from 2010 to 2024, with 50 completing the modified NPD protocol, 2 failing to tolerate the procedure, and 3 having inconclusive results. Fourty-eight results were normal, and 2 abnormal. In the normal group, the basal potential difference (PD) averaged −17 ± 6 mV, amiloride response was 7 ± 3 mV, and chloride-free + isoproterenol response was −9 ± 5 mV. The two abnormal results were observed in a 12-month-old with failure to thrive and a 6-day-old with meconium plug, presenting with basal PD of −30 mV and −28 mV respectively, with no cAMP response. CF was diagnosed in the 12-month-old based on clinical symptoms and sweat test of 70 meq/L. The 6-day-old, is being followed for mild asthma with normal repeat sweat testing. None of the children with normal NPD results were diagnosed with CF. Conclusion: –NPD testing is feasable in very young children. This protocol could be valuable for investigating cases of CF screened positive indeterminate diagnosis (CFSPID) or CF metabolic syndrome (CFMS), and for pre- and post-testing in clinical trials. Further validation studies are warranted.