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Revisiting sweat chloride test results based on recent guidelines for diagnosis of cystic fibrosis
Jayson V Pagaduan1, Mahesheema Ali1, Michael Dowlin1
1Department of Pathology & Immunology, Baylor College of Medicine, Department of Pathology and Immunology, Texas Children's Hospital, Houston, TX 77030, USA.
Insights
The updated Cystic Fibrosis Foundation guidelines reclassified 125 patients, increasing the detection of potential cystic fibrosis (CF) cases. Combining sweat chloride tests with CFTR gene analysis aids in earlier diagnosis and intervention.
Area of Science:
- Medical Diagnostics
- Genetics
- Pulmonology
Background:
- The Cystic Fibrosis Foundation recently updated sweat chloride concentration guidelines for diagnosing cystic fibrosis (CF).
- The intermediate range for sweat chloride concentration was revised from 40-59 mmol/L to 30-59 mmol/L for individuals over six months old.
Purpose of the Study:
- To evaluate the impact of the revised Cystic Fibrosis Foundation sweat chloride guidelines on CF detection.
- To assess how the new guidelines would reclassify patients previously tested at Texas Children's Hospital.
Main Methods:
- A retrospective analysis of 3012 sweat chloride test results from the past five years was conducted.
- Patient data was re-evaluated based on the updated Cystic Fibrosis Foundation diagnostic criteria.
Main Results:
- The revised guidelines reclassified 125 patients into the intermediate sweat chloride value range, who were previously considered unlikely to have CF.
- Of those tested for CFTR gene mutations, 32% were positive, with 50% having two CFTR mutations, though diagnosed with CFTR-related metabolic syndrome.
Conclusions:
- The updated guidelines, incorporating a lower intermediate sweat chloride threshold (30-59 mmol/L) and CFTR genetic analysis, improve the identification of individuals at risk for or with CF.
- This enhanced diagnostic approach facilitates earlier therapeutic interventions for cystic fibrosis.
Objectives:
Recent sweat chloride guidelines published by the Cystic Fibrosis Foundation changed the intermediate sweat chloride concentration range from 40-59 mmol/L to 30-59 mmol/L for age > 6 months. We wanted to know how this new guideline would impact detection of cystic fibrosis among patients who previously had sweat tests done at Texas Children's Hospital.
Methods:
We revisited sweat chloride test results (n = 3012) in the last 5 years at Texas Children's Hospital based on the new guidelines on diagnosis of cystic fibrosis from the Cystic Fibrosis Foundation.
Results:
We identified 125 patients that would be reclassified in the intermediate sweat chloride value with the new guidelines that were classified as "unlikely to have CF" in the previous guidelines. 8 (32%) patients with CFTR gene testing were positive for CFTR gene mutation(s). 4 (50%) of these patients were identified to have 2 CFTR mutations. One had variant combination that was reported to cause CF but all were diagnosed with CFTR-related metabolic syndrome.
Conclusion:
Our findings concur with the new CF diagnosis guidelines that changing the intermediate cut-off to 30-59 mmol/L sweat chloride concentration in combination with CFTR genetic analysis enhances the probability of identifying individuals that have risk of developing CF or have CF and enables for earlier therapeutic intervention.
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