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Abstract
Background
Cystic fibrosis is a chronic progressive autosomal recessive disorder caused by the CFTR gene mutations. It is quite common in Caucasians, but very rare in Asians. Sweat chloride test is known to be a screening test for the cystic fibrosis due to the fact that electrolyte levels in sweat are elevated in patients. In this study, sweat chloride levels in Korean population were measured and analyzed by using standardized pilocarpine iontophoresis sweat chloride test.
Methods
The sweat chloride test was performed in 47 patients referred to Yondong Severance Hospital from August, 2001 to April, 2007 and 41 healthy volunteers. The sweat chloride tests were conducted according to the CLSI C34-A2 guideline using pilocarpine iontophoresis method, and the chloride concentrations in sweat were measured by mercurimetric titration.
Results
Four patients showed sweat chloride concentrations higher than 60 mmol/L. Reference interval was calculated as 1.4-44.5 mmol/L by analysis of the results of healthy volunteers (n=41). Four patients who exhibited high sweat chloride levels, had characteristic clinical features of cystic fibrosis and their diagnoses were confirmed either by repeated sweat chloride test or genetic analysis.
Conclusions
Standardized sweat chloride test can be utilized as a useful diagnostic tool for cystic fibrosis in Koreans. In cases of sweat chloride levels higher than 40 mmol/L, the test should be repeated for the possible diagnosis of cystic fibrosis. All the confirmed Korean cases of cystic fibrosis showed sweat chloride level above 60 mmol/L.
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Fig. 1.
The histogram of sweat chloride concentrations of cystic fibrosis patients and healthy volunteers. Only repeated results are presented in patients with duplicate results.
Fig. 2.
The plot of differences of sweat chloride concentration between two sites (right and left) of each subject. The lines indicate the acceptable range of difference according to the CLSI guideline. Only repeated results are presented in patients with duplicate results.
Table 1.
The characteristics of study population
| Item | Patients (N=47) | Healthy volunteers (N=41) |
|---|---|---|
| Male gender [N (%)] | 27 (57.4%) | 13 (31.7%) |
| Mean age (range) | 13 yr (3 months-53 yr) | 29 yr (12-49 yr) |
Table 2.
The clinical features of patients with high sweat chloride concentrations
| No. case | Sex | Age (yr) |
Sweat chloride concentration (mmol/L) Right (repeated result)/Left (repeated result) |
Respiratory symptoms∗ | Gastro-intestinal symptoms† | Genetic analysis |
|---|---|---|---|---|---|---|
| 1‡ | F | 13 | 108.1 (105.9)/169.1 (87.5) | + | + | Compound heterozygote (X1291/5T-V470) |
| 2‡ | F | 5 | 97.5 (75.4)/92.4 (79.5) | + | - | Polymorphism (2694T/G) |
| 3§ | M | 15 | 73.7 (66.2)/29.5 (59.9) | + | - | Compound heterozygote (Q98R/Q220X) |
| 4 | F | 17 | 99.3/105.6 | + | - | Compound heterozygote (delEx14A/IVS17a-26A>G) |
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