Diagnostic sweat testing: the Cystic Fibrosis Foundation guidelines.
The Cystic Fibrosis Foundation (CFF) accredits cystic fibrosis (CF) centers, located in teaching and community hospitals nationwide, which provide comprehensive diagnosis and treatment for people with CF. The CF centers are evaluated by the CFF Center Committee according to specific criteria covering the areas of clinical care, teaching, and research. There are specific requirements for sweat testing, and adherence to them is required for accreditation. In 2006, the CFF Center Committee distributed a sweat testing guidelines memorandum to the CF center directors. Although the guidelines are based on the Clinical Laboratory Standards Institute (CLSI), formerly National Committee for Clinical Laboratory Standards, sweat testing document C34-A2 and the College of American Pathologists (CAP) Laboratory Accreditation Program Inspection Checklist items for sweat testing, they are more prescriptive for uniformity and are focused on diagnostic rather than screening sweat tests. The guidelines are applicable to patients of all ages undergoing sweat chloride testing.
Adherence to the guidelines is mandatory for CFF centers; however, the requirements are appropriate and adaptable for any facility performing diagnostic testing for CF. Although it may be ideal for sweat testing to be centralized at CF centers, in practice this does not occur. According to enrollment in a national proficiency testing program for sweat analysis, more than 600 laboratories performed sweat testing in 2006. With widespread implementation of newborn screening programs for CF, the reliance on a well-performed and well-interpreted sweat test is critical to the success of accurately diagnosing CF. Sweat chloride testing should be performed on all infants with a positive newborn screen even in cases in which two CF-causing mutations have been identified.
The following represent the 2006 CFF sweat testing guidelines, along with commentary discussing the specific guidelines.