Dataset Information

β-adrenergic sweat test in children with inconclusive cystic fibrosis diagnosis: Do we need new reference ranges?

ABSTRACT:

Background

Investigating inconclusive cystic fibrosis (CF) diagnosis in children is difficult without advanced cystic fibrosis transmembrane conductance regulator (CFTR) function tests. This study investigated the utility of beta (β)-adrenergic sweat test to exclude CF in participants with inconclusive diagnosis (CF suspects) in South Africa.

Methods

β-adrenergic sweat test and sweat chloride tests (SCT) were performed simultaneously in CF suspects and adult controls (healthy, CFTR heterozygotes and CF). Cholinergic and β-adrenergic induced sweat rate was measured by evaporimetry (transepithelial water loss [TEWL]: g H₂ O/m² /h) following intradermal injections. Next-generation sequencing of CFTR was performed in CF suspects. CF diagnosis was defined by genotype.

Results

Thirty-seven controls (10 healthy, 14 CF, 13 CFTR heterozygotes) and 32 CF suspects (26 children; 6 adults) were enrolled. Six were excluded from formal analyses due to β-adrenergic sweat test failure. In adults, evaporimetry was superior to SCT for diagnosis of CF with β-adrenergic:cholinergic ratio TEWL ≤ 0.05 achieving 100% sensitivity and specificity. Twenty-two CF suspect children (age range: 3.4-15.6 years) completed β-adrenergic sweat testing of which none had CF confirmed by genotyping: β-adrenergic:cholinergic ratio > 0.05 successfully excluded CF in all but one child who was CFTR heterozygous. Median peak β-adrenergic TEWL and β-adrenergic:cholinergic ratio in CFTR negative and CFTR heterozygous children was significantly lower than adult controls.

Conclusion

β-adrenergic sweat test is more accurate than SCT for excluding CF in children with inconclusive diagnosis. Established reference ranges for β-adrenergic sweat test may not be suitable for children due to lower β-adrenergic sweat secretion compared to adults.

SUBMITTER: Zampoli M

PROVIDER: S-EPMC10092537 | biostudies-literature | 2023 Jan

REPOSITORIES: biostudies-literature

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Publications

β-adrenergic sweat test in children with inconclusive cystic fibrosis diagnosis: Do we need new reference ranges?

Zampoli Marco M Verstraete Janine J Nguyen-Khoa Thao T Sermet-Gaudelus Isabelle I Zar Heather J HJ Gonska Tanja T Morrow Brenda M BM

Pediatric pulmonology 20221017 1

<h4>Background</h4>Investigating inconclusive cystic fibrosis (CF) diagnosis in children is difficult without advanced cystic fibrosis transmembrane conductance regulator (CFTR) function tests. This study investigated the utility of beta (β)-adrenergic sweat test to exclude CF in participants with inconclusive diagnosis (CF suspects) in South Africa.<h4>Methods</h4>β-adrenergic sweat test and sweat chloride tests (SCT) were performed simultaneously in CF suspects and adult controls (healthy, CFT ...[more]

PMID: 36193559

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Project description:The current guidelines for sweat chloride analysis identify the procedures for sweat collection, but not for chloride assay, which is usually performed by methods originally not aiming at the low concentrations of chloride found in sweat. To overcome this limitation, we set up, characterized, and adopted an original inductively coupled plasma mass spectrometry (ICP-MS) method for sweat chloride determination, which was designed for its easy use in a clinical laboratory. The method was linear in the range 8.5E-3 to 272.0E-3 mM, precision exhibited a relative standard deviation <?6%, and accuracy was in the range 99.7-103.8%. Limit of blank, limit of detection, and limit of quantitation were 2.1 mM, 3.2 mM, and 7.0 mM, respectively, which correspond to real concentrations injected into the mass spectrometer of 3.9E-3 mM for LOD and 8.5E-3 mM for LOQ. At first, the method was tested on 50 healthy volunteers who exhibited a mean chloride concentration of 15.7 mM (25-75th percentile 10.1-19.3 mM, range 2.8-37.4 mM); then, it was used to investigate two patients with suspected cystic fibrosis, who exhibited sweat chloride values of 65.6 mM and 81.2 mM, respectively. Moreover, the method was cross-validated by assaying 50 samples with chloride concentration values in the range 10-131 mM, by both ICP-MS and coulometric titration, which is the technology officially used in Tuscany for cystic fibrosis newborn screening. The reference analytical performances and the relatively low cost of ICP-MS, accompanied by the advantageous cost of a single sweat chloride assay, make this technology the best candidate to provide a top reference method for the quantification of chloride in sweat. The method that we propose was optimized and validated for sweat samples ??75 mg, which is the minimum amount requested by the international protocols. However, the method sensitivity and, in addition, the possibility to reduce the sample dilution factor, make possible the quantification of chloride even in samples weighting <?75 mg that are discarded according to the current guidelines. Graphical abstract.

Project description:BackgroundSome infants undergoing newborn screening (NBS) tests have inconclusive sweat chloride test (SCT) results that lead to the designation of Cystic Fibrosis Screen Positive, Inconclusive Diagnosis/CFTR-related metabolic syndrome (CFSPID/CRMS). Some proportion of them transition to a CF diagnosis, but no predictive markers can stratify which are at risk for this transition. We report single-center outcomes of children with CRMS.MethodsWe retrospectively identified all infants born in Alabama from 2008 through 2020 referred to our CF Center with an elevated immunoreactive trypsinogen level (IRT) associated with a cystic fibrosis transmembrane conductance regulator (CFTR) mutation (IRT+/DNA+) who had at least one SCT result documented. Infants were classified per established guidelines as Carrier, CRMS, or CF based on the IRT+/DNA+ and SCT results. The electronic health record was reviewed for follow-up visits until the children received a definitive diagnosis (to carrier or CF) according to current diagnostic guidelines for CF, or through the end of the 2020 year.ResultsOf the 1,346 infants with IRT+ and at least 1 CFTR mutation identified (IRT+/DNA+), 63 (4.7%) were designated as CRMS. Of these infants, 12 (19.1%) transitioned to Carrier status (CRMS-Carrier), 40 (63.5%) of them remained CRMS status (CRMS-Persistent) and 11 (17.5%) of them transitioned to a diagnosis of CF (CRMS-CF). Of the 11 children in the CRMS-CF group, 4 (36%) had an initial SCT 30-39 mmol/L, 4 (36%) had an initial SCT 40-49 mmol/L and 3 (27%) had an initial SCT 50-59 mmol/L. These children also had higher initial sweat tests and greater yearly increases in sweat chloride values than others with CRMS. We found that in comparison to children in the CRMS-P group, a greater proportion of children in the CRMS-CF group cultured bacteria like methicillin-resistant Staphylococcus aureus, Stenotrophomonas maltophilia, and Pseudomonas aeruginosa, had smaller weight-for-height percentiles and remained smaller over time despite slightly greater growth.ConclusionInfants with an inconclusive diagnosis of CF should continue to receive annual care and management given their potential risk of transition to CF. Further research is needed to assess whether certain phenotypic patterns, clinical symptoms, diagnostic tests or biomarkers could better stratify these children.

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Dataset Information

β-adrenergic sweat test in children with inconclusive cystic fibrosis diagnosis: Do we need new reference ranges?

Background

Methods

Results

Conclusion

Publications

β-adrenergic sweat test in children with inconclusive cystic fibrosis diagnosis: Do we need new reference ranges?

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