Nanoduct Sweat Conductivity Measurements in 2664 Patients: Relationship to Age, Arterial Blood Gas, Serum Electrolyte Profiles and Clinical Diagnosis

BACKGROUND: The Nanoduct(®) device has acceptable diagnostic accuracy, but there is not enough systematic data supporting its usage in the diagnosis of cystic fibrosis (CF). METHODS: A retrospective review of patients with an indication for the sweat test was conducted. The conductivity test was repeated in patients who had values higher than 60 mmol/L, and they were referred for sweat chloride measurements. Associations between sweat conductivity measurements and age, gender, (pH, HCO(3), pCO(2), Na, K, Cl), family history, consanguinity, indications for the test and number of hospitalization were studied. RESULTS: Among 2,664 patients, 16 children had sweat conductivity values higher than 80. The median age of patients diagnosed with CF was 4 months old. Age, pH, HCO(3), Na, Cl, K and the sweat conductivity test were statistically related (P < 0.001). The ROC curve showed very high agreement between the 2nd conductivity test and the sweat test. CONCLUSIONS: Patients suspected to have CF can be screened using the Nanoduct(®) conductivity device in non-qualified centers.