Biochemical and genetic tools to predict the progression to Cystic Fibrosis in CRMS/CFSPID subjects: A systematic review.

Objectives: Aim of this study was to identify risk factors for a progression to cystic fibrosis (CF) in individuals detected as CF Screening Positive, Inconclusive Diagnosis (CFSPID).

Methods: This is a systematic review through literature databases (2015-2023). Blood immunoreactive trypsinogen (b-IRT) values, CFTR genotype, sweat chloride (SC) values, isolation of Pseudomonas aeruginosa (Pa) from respiratory samples, Lung Clearance Index (LCI) values in CFSPIDs who converted to CF (CFSPID > CF) and age at CF transition were assessed.

Results: Percentage of CFSPID > CF varies from 5.3 % to 44 %. Presence of one CF-causing CFTR variant in trans with a variant with variable clinical consequences (VVCC), an initial SC ≥ 40 mmol/L, an increase of SC > 2.5 mmol/L/year and recurrent isolation of pseudomonas aeruginosa (Pa) from airway samples could allow identification of subjects at risk of progression to CF.

Conclusions: CFSPIDs with CF causing variant/VVCC genotype and first SC in the higher borderline range may require more frequent and prolonged clinical follow-up.