Sweat test and cystic fibrosis: overview of test performance at public and private centers in the state of São Paulo, Brazil

OBJECTIVE: The sweat test (ST) measures chloride levels in sweat and is considered the gold standard for the diagnosis of cystic fibrosis (CF). However, the reliability of a ST depends on their being performed by experienced technicians and in accordance with strict guidelines. Our aim was to evaluate how sweat stimulation, sweat collection, and chloride measurement are performed at 14 centers (9 public centers and 5 private centers) that routinely perform STs in the state of São Paulo, which has the highest frequency of CF in Brazil. METHODS: This was a cross-sectional cohort study, using a standardized questionnaire administered in loco to the staff responsible for conducting STs. RESULTS: No uniformity regarding the procedures was found among the centers. Most centers were noncompliant with the international guidelines, especially regarding the collection of sweat (the samples were insufficient in 10-50% of the subjects tested); availability of stimulation equipment (which was limited at 2 centers); modernity and certification of stimulation equipment (most of the equipment having been used for 3-23 years); and written protocols (which were lacking at 12 centers). Knowledge of ST guidelines was evaluated at only 1 center. CONCLUSIONS: Our results show that STs largely deviate from internationally accepted guidelines at the participating centers. Therefore, there is an urgent need for standardization of STs, training of qualified personnel, and acquisition/certification of suitable equipment. These are essential conditions for a reliable diagnosis of CF, especially with the increasing demand due to newborn screening nationwide, and for the assessment of a possible clinical benefit from the use of modulator drugs.