Cystic Fibrosis (CF) (IRT)

The NEONATAL IRT Screening ELISA is a sandwich ELISA in which capture anti-IRT antibodies recognize native IRT in the blood specimen. The reduction of 3.3’-5.5’-tetramethylbenzidine (TMB) by Horseradish Peroxidase (HRP)-labelled detection antibody will generate an absorbance signal. The measured absorbance signal intensity is proportional to the concentration of IRT in the test sample.

Cystic fibrosis is caused by a genetic defect in the Cystic Fibrosis Transmembrane conductance Regulator (CFTR) gene, which encodes a chloride channel. This chloride ion concentration regulatory protein is present in all exocrine tissues. Cystic fibrosis symptoms in newborns include thick and viscous secretions in the lungs, pancreas, liver, intestines and reproductive system, caused by the defect in the transport of these ions by the CFTR protein. The increase in sweat salt concentration is also noticeable. 

Patients with typical cystic fibrosis develop early multisystemic disease involving several or all of the organs mentioned above. Typical pulmonary manifestations are consistent with obstructive airway disease and include persistent and productive cough. Pancreatic insufficiency usually results in diabetes and pancreatitis. Meconium ileus (obstruction of the intestine by meconium in a newborn), a cystic fibrosis symptom in newborns, is present in 10 to 20% of affected babies. More than 95% of affected men are sterile, with female fertility being more moderately compromised.

A cystic fibrosis diagnosis in newborn usually involves two sequential tests: infants with abnormal results for the first test are retested with a second confirmatory test.

The first-line screening test generally refers to an Immunoreactive trypsinogen assay (IRT). With regard to second-line tests, however, several approaches exist. If IRT is positive, some screening protocols directly consider molecular CFTR testing, while others prefer to perform IRT testing on a second sample before considering molecular testing. A new parameter, PAP (Pancreatitis-Associated Protein), was recently introduced as a second-line confirmation marker, prior to the implementation of the molecular test.