X-ray microanalysis of chloride in nails from cystic fibrosis and control patients.

Nail clippings from 60 individuals were examined. There were 34 "old" (greater than 16 years) controls, 16 "young" controls and 10 CF patients. In regard to elements found, Si and Al were considered as exogenous contamination. Other elements examined were variable in both control and CF. Examination of the Cl levels among the 3 groups showed a highly significant difference between the mean Cl integral values of the young controls (619 integral) and the CF patients (2956 integral). The results of the older control population ranged from 0-905 integral with a mean of 269 integral. We found no age or sex difference in the amount of Cl or any other element from either the CF or control population. Results show that the x-ray energy dispersive system (EDS) is very useful in studying the Cl in nails. We found that examination of nails frozen in liquid nitrogen followed by fracturing without prior washing was the preferred method. Although the results of this study clearly show statistically the value of EDS analysis of Cl in the diagnosis of CF, we must await further study of a larger group of patients to determine its usefulness in evaluating individual patients, particularly newborns.