The diagnosis of cystic fibrosis is based on characteristic clinical symptoms and either a positive sweat test (ST) or identification of related mutations on each of Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) gene alleles. A significant number of patients have no definite diagnosis, having possibly related symptoms, borderline sweat test and no identifiable known mutation on the CFTR gene. Nasal potential difference (NPD) is an established method of diagnosis in these patients. Until now standard values for very young patients have not been developed and validated.
Aim: to evaluate the feasibility of NPD in young children.
Methods: The standard protocol for NPD was adapted for young children. In the standard protocol infusions of amiloride, chloride-free and isoproterenol are for 3 minutes. In the current protocol this was reduced to 2 minutes so the entire test is completed in 10 minutes.
Results: 34 children aged 2 months to 3 years of age were enrolled in the study. Diagnoses included FTT (12), chronic diarrhea (6), respiratory problems (10) meconium plug (2), mean sweat test 53mmol/L. The NPD was abnormal in 6 patients and tolerated in all children
Conclusion: NPD is feasible in young children and may be useful in the diagnosis of CF in questionable cases.
