OBJECTIVE: To conduct a descriptive analysis of the sweat test (ST), associating 
ST results with epidemiological data, CFTR (cystic fibrosis transmembrane 
conductance regulator) mutations and reasons to indicate the ST, as well as 
correlating sweat sodium and sweat chloride concentrations in subjects.
METHODS: Retrospective survey and descriptive analysis of 5,721 ST at a 
university referral center.
RESULTS: The inclusion of the subjects was based on clinical data related with 
cystic fibrosis (CF) phenotype. The samples were grouped by (i) sweat chloride 
concentrations (mEq/L): <30: 3,249/5,277 (61.6%); ≥30 to <60: 1,326/5,277 
(25.1%); ≥60: 702/5,277 (13.3%) and (ii) age: (Group A--GA) 0 to <6 months; 
(Group B--GB) ≥6 months to <18 years; (Group C--GC) ≥18 years. Digestive 
symptoms showed higher prevalence ratio for the CF diagnosis as well as 
association between younger age and higher values of sweat chloride, sweat 
sodium, and chloride/sodium ratio. The indication of ST due to respiratory 
symptoms was higher in GB and associated with greater age, lower values of sweat 
chloride, sweat sodium, and chloride/sodium ratio. There was higher prevalence 
of ST with sweat chloride levels <30 mEq/L in GB, ≥60 mEq/L in GC, and with 
borderline level in GB. There was positive correlation between sweat sodium and 
sweat chloride. Sweat chloride/sweat sodium and sweat sodium-sweat chloride 
indexes showed association with sex, reason for ST indication, and CFTR 
mutations. Sex alters some values presented in the ST. The number of ST/year 
performed before and after the newborn screening implementation was the same; 
however, we observed a higher number of borderlines values. A wide spectrum of 
CFTR mutation was found. Severe CFTR mutations and F508del/F508del genotype were 
associated with highest probability of ST chloride levels ≥60 mEq/L, and the 
absence of CFTR mutations identified was associated with borderline ST and 
respiratory symptoms.
CONCLUSIONS: ST data showed wide variability dependent on age, sex, reason for 
examination indication, CFTR mutations, and weight of the collected sweat 
sample. Sweat sodium concentration is directly correlated with sweat chloride 
levels and it could be used as a quality parameter.