Quality of sweat test performance in the diagnosis of cystic fibrosis.

The sweat test, correctly performed, appears to be reliable, but results were found to be unreliable about half the time in 84 small community hospitals assessed. The reasons are inexperienced and untrained technicians, the infrequency of test performance, the use of unstandardized equipment, and the lack of appropriate standards. It behooves all clinical laboratory directors to re-examine and standardize their procedures and use the recommendations of the Cystic Fibrosis Foundation. Physicians should be made aware of the current situation and send their patients only to laboratories that perform the test reliably.