RT Journal A1 Hicks JM T1 SWeat tests JF JAMA JO JAMA YR 1979 FD May 25 VO 241 IS 21 SP 2264 OP 2265 DO 10.1001/jama.1979.03290470016013 UL http://dx.doi.org/10.1001/jama.1979.03290470016013 AB To the Editor.—  I feel obliged to reply to Dr Shwachmann's letter (240:2731, 1978) regarding the high frequency of unreliable sweat tests for cystic fibrosis and his statement that the cause is the lack of interest of clinical chemists. I agree that sweat tests are frequently not performed reliably, but I wonder why the clinical chemist has been singled out as being responsible when most hospital laboratories are still directed by pathologists and not by professional clinical chemists. Certainly in our laboratory the sweat test is performed exactly as described by the Cystic Fibrosis Foundation in its publication, Procedure for the Quantitative Iontophoretic Sweat Test for Cystic Fibrosis, by Gibson, Sant' Agnese, and Shwachmann. We report the weight of sweat collected and the concentration of sodium and chloride and run the test twice. In addition to our laboratory, I know of many other hospital clinical chemistry laboratories in which the