Diagnosis of cystic fibrosis with chloride meter (Sherwood M926S chloride analyzer®) and sweat test analysis system (CFΔ collection system®) compared to the Gibson Cooke method.

Abstract

Sweat test with Gibson Cooke (GC) method is the diagnostic gold standard for cystic fibrosis (CF). Recently, alternative methods have been introduced to simplify both the collection and analysis of sweat samples. Our aim was to compare sweat chloride values obtained by GC method with other sweat test methods in patients diagnosed with CF and whose CF diagnosis had been ruled out. We wanted to determine if the other sweat test methods could reliably identify patients with CF and differentiate them from healthy subjects. Chloride concentration was measured with GC method, chloride meter and sweat test analysis system; also conductivity was determined with sweat test analysis system. Forty eight patients with CF and 82 patients without CF underwent the sweat test, showing median sweat chloride values 98.9 mEq/L with GC method, 101 mmol/L with chloride meter, 87.8 mmol/L with sweat test analysis system. In non-CF group, median sweat chloride values were 16.8 mEq/L with GC method, 10.5 mmol/L with chloride meter, and 15.6 mmol/L with sweat test analysis system. Median conductivity value was 107.3 mmol/L in CF group and 32.1 mmol/L in non CF group. There was a strong positive correlation between GC method and the other sweat test methods with a statistical significance (r=0.85) in all subjects. Sweat chloride concentration and conductivity by other sweat test methods highly correlate with the GC method. We think that the other sweat test equipments can be used as reliably as the classic GC method to diagnose or exclude CF.