Sweat testing for cystic fibrosis: A review of New Zealand laboratories

Abstract

Evolving diagnostic criteria for cystic fibrosis, broadening of the populations being tested and the need to interpret intermediate sweat test results have imposed a much greater need to standardize the collection and analysis of sweat. To identify variations in sweat testing in New Zealand laboratories and compare these with guidelines from the UK and the USA. All laboratories in New Zealand offering sweat testing were identified and data collected from these laboratories by structured questionnaire. There were no New Zealand laboratories that conformed to either set of guidelines. Inconsistencies were observed in minimum sweat quantities, the nature of the iontophoresis solution, the sweat electrolytes analysed, quoted reference ranges and recommendations made as a consequence of the result. Conformity to the guidelines would help to minimize variation in sweat testing in New Zealand. Performance of a sufficient number of tests to maintain expertise is critical, but geographical constraints make patient travel to distant centres difficult in a small, scattered population. A possible solution, where numbers permit, may be the collection of sweat locally, with referral to a major laboratory for analysis. This is only possible with adequate training in collection and follow-up audit of the sweat testing procedure both in the collection and in the analytical phase.