Objective: Sweat chloride measurement is considered a standard
diagnostic tool for cystic fibrosis (CF). This study was performed to
compare sweat chloride values obtained by quantitative pilocarpine
iontophoresis (classic test) with sweat crystallization detected by
direct observation of a drop of perspiration under light microscopy in
patients with and without CF. Methods: The tests using both techniques
were performed simultaneously in patients with and without CF. Cutoff
values of ≥60 mmol/L of chloride concentration for the classic
sweat test was considered for diagnosis of CF. In crystallization
method, observation of typical dendritic forms of salt crystals under
light microscopy was interpreted positive. Findings: Sixty patients
suspected to CF (31 males and 29 females) with age range of 9 months to
2 years underwent the sweat test using both techniques. Median sweat
chloride values was 26.13+10.85 in group with negative and 72.76+12.78
mmol/L in group with positive sweat test, respectively. All the
patients who had positive sweat test in classic method showed typical
dendritic forms of salt crystal in sweat crystallization test, which
provided the test with 100% sensitivity (95%CI: 93.1-100). Only one of
the 31 subjects with negative results for classic sweat test had
positive result for crystallization sweat test, which provided the test
with 96.7% specificity (95%CI: 92.9-100). Time spent to perform the
crystallization test was significantly shorter than the classic method
whereas its cost was also lower than the second method. Conclusion:
There was a good correspondence between two studied methods of sweat
test. These results suggested the sweat crystallization test as an
alternative test for detecting CF disease with high sensitivity and
specificity