A
sweat test is a diagnostic procedure primarily used to diagnose
cystic fibrosis (CF). It measures the concentration of chloride in the sweat, which is typically elevated in individuals with CF. The
sweat glands are stimulated to produce sweat, which is then collected and analyzed.
The sweat test is a non-invasive procedure. It generally involves three main steps:
Stimulation: A chemical called
pilocarpine is applied to a small area of the skin, usually on the forearm. An electrode is then used to stimulate the sweat glands.
Collection: Sweat is collected on a piece of gauze or filter paper over a period of about 30 minutes.
A sweat test is recommended for children and infants who exhibit symptoms of cystic fibrosis, such as chronic
lung infections, persistent cough, poor growth, and frequent greasy stools. It is also suggested for newborns who have had a positive newborn screening test for CF.
The results of the sweat test can be categorized into three ranges:
Normal: Chloride levels are below 30 mmol/L for infants younger than 6 months, and below 40 mmol/L for older children and adults.
Intermediate: Chloride levels are between 30-59 mmol/L for infants and 40-59 mmol/L for older children and adults. Additional testing may be required.
Positive: Chloride levels are 60 mmol/L or higher, indicating a high likelihood of cystic fibrosis.
The sweat test is generally safe and painless. Some children may experience mild skin irritation where the electrodes were applied. However, significant side effects are rare.
The sweat test is considered the "gold standard" for diagnosing cystic fibrosis. It has a high sensitivity and specificity when performed correctly. However, borderline or intermediate results may require additional genetic testing or repeat testing to confirm the diagnosis.
If the sweat test results indicate a high chloride concentration, further diagnostic evaluation is needed. This includes genetic testing to identify mutations in the
CFTR gene associated with cystic fibrosis. Early diagnosis and management are crucial for improving the quality of life and lifespan for children with CF.
Conclusion
The sweat test is a crucial diagnostic tool in pediatrics for identifying cystic fibrosis. It is non-invasive, reliable, and provides essential information that guides further diagnostic and therapeutic steps. Early detection and management can significantly enhance outcomes for affected children.
