Published in:
Open Access
01-12-2016 | Research
Quality of sweat test (ST) based on the proportion of sweat sodium (Na) and sweat chloride (Cl) as diagnostic parameter of cystic fibrosis: are we on the right way?
Authors:
Alethéa Guimarães Faria, Fernando Augusto Lima Marson, Carla Cristina de Souza Gomez, Maria Ângela Gonçalves de Oliveira Ribeiro, Lucas Brioschi Morais, Maria de Fátima Servidoni, Carmen Sílvia Bertuzzo, Eulália Sakano, Maura Goto, Ilma Aparecida Paschoal, Mônica Corso Pereira, Gabriel Hessel, Carlos Emílio Levy, Adyléia Aparecida Dalbo Contrera Toro, Andressa Oliveira Peixoto, Maria Cristina Ribeiro Simões, Elizete Aparecida Lomazi, Roberto José Negrão Nogueira, Antônio Fernando Ribeiro, José Dirceu Ribeiro
Published in:
Diagnostic Pathology
|
Issue 1/2016
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Abstract
Background
To assess the quality of sweat test (ST) based on the proportion of sweat sodium and sweat chloride as diagnostic parameter of cystic fibrosis (CF).
Methods
A retrospective study of 5,721 sweat samples and subsequent descriptive analysis were carried out. The test was considered “of good quality” (correct) when: (i) sweat chloride was lower than 60 mEq/L, and sweat sodium was higher than sweat chloride; (ii) sweat chloride was higher than 60 mEq/L, and sweat sodium was lower than sweat chloride.
Results
The study included 5,692/5,721 sweat samples of ST which had been requested due to clinical presentations compatible with CF and/or neonatal screenings with altered immunoreactive trypsinogen values. Considering the proportion of sweat sodium and sweat chloride as ST quality parameter, the test was performed correctly in 5,023/5,692 (88.2 %) sweat samples. The sweat chloride test results were grouped into four reference ranges for chloride (i) chloride < 30 mEq/L: 3,651/5,692 (64.1 %); (ii) chloride ≥ 30 mEq/L to < 40 mEq/L: 652/5,692 (11.5 %); (iii) ≥ 40 mEq/L to < 60 mEq/L: 673/5,692 (11.8 %); (iv) ≥ 60 mEq/L: 716/5,692 (12.6 %). In the comparative analysis, there was no association between ST quality and: (i) symptoms to indicate a ST [respiratory (p = 0.084), digestive (p = 0.753), nutritional (p = 0.824), and others (p = 0.136)], (ii) sweat weight (p = 0.416). However, there was a positive association with: (i) gender, (ii) results of ST (p < 0.001), (iii) chloride/sodium ratio (p < 0.001), (iv) subject’s age at the time of ST [grouped according to category (p < 0.001) and numerical order (p < 0.001)]. For the subset of 169 patients with CF and two CFTR mutations Class I, II and/or III, in comparative analysis, there was a positive association with: (i) sweat chloride/sodium ratio (p < 0.001), (ii) sweat chloride values (p = 0.047), (iii) subject’s age at the time of the ST grouped by numerical order (p = 0.001).
Conclusions
Considering that the quality of ST can be assessed by levels of sweat sodium and sweat chloride, an increasing number of low-quality tests could be observed in our sweat samples. The quality of the test was associated with important factors, such as gender, CF diagnosis, and subjects’ age.