Guidelines for the performance of the sweat test for the diagnosis of cystic fibrosis

Abstract

AddressesA multidisciplinary group (representing various professional bodies and supported by the Cystic Fibrosis Trust) has developed evidence-based guidelines for the performance of the sweat test in the UK. The guidelines cover patient information, subject suitability, sweat collection, sweat analysis, quality, interpretation of results, and responsibility for testing and training. The guidelines were produced following a detailed literature search by the process described by the Royal College of Paediatrics and Child Health (RCPCH), using the Scottish Intercollegiate Guidelines Network 1 (SIGN 1) criteria to grade the evidence. Recommendations are graded A, B, or C, depending on the level of evidence. The grade B recommendations (there were no grade A recommendations) were subsequently appraised and endorsed as part of the RCPCH process, according to Appraisal of Guidelines for Research and Evaluation in Europe (AGREE). The recommendations are summarized in tabular form representing the final version incorporating the comments from the appraisal process. Both the appraisal comments and the full evidence base can be found on www.rcpch.ac.uk/publications/clinical_docs.html. The full guidelines can also be found on

High sweat electrolytes in a malnourished child

“…4 Great care should be taken to prevent evaporation. 1,5 Hence sweat is collected only for 30 min in our laboratory. The measurement of sweat chloride and not the sodium concentration is the definitive test for diagnosis.…”

“…The measurement of sweat chloride and not the sodium concentration is the definitive test for diagnosis. 1,5 Chloride concentration >60 mmol/L is strongly suggestive of CF. 5 The sweat chloride can be measured by colorimetry (titrimetric or spectro photometric), coulometry (chloridometer) or ion-selective electrode technique.…”

“…5 Sodium concentration must not be measured alone. 1,5 In our laboratory we measure both sodium and chloride by ion-selective electrode technique. The sweat test was performed on this patient once his skin lesions were healed, as this patient had some of the features of cystic fibrosis.…”

“…1 Hence it is carried out in our hospital in patients who present with recurrent respiratory tract infections and chronic diarrhea to find out a cause when the other investigations do not help. A sweat chloride concentration of >60 mmol/L, strongly supports the diagnosis of CF.…”

Sweat testing: can the conductivity analysis take the place of the classic Gibson and Cooke technique?

“…Contudo, os sujeitos com FC examinados tinham mais de 18 meses (a idade dos sujeitos sem FC não foi fornecida) e o tempo de coleta após estimulação durou de 30 a 60 minutos. Sabe-se que um tempo de coleta prolongado pode favorecer a taxa de sucesso, mas também pode alterar a concentração de eletrólitos: por essa razão, o tempo padrão recomendado é de 30 minutos 2,11,12 . Outros estudos sugerem que a taxa de falha com a coleta feita com o Macroduct ® é mais alta, especialmente nos primeiros meses de vida, e que a taxa de sucesso é mais alta com o sistema clássico 6,7 .…”