Cellular Markers in Treated or Untreated Non-tuberculous Mycobacterial Respiratory Infection in Patients With Cystic Fibrosis

Background: Evidence shows that Non-tuberculous Mycobacterial (NTM) infections have increased and are 1,000 to 8,000 times more frequent in patients with cystic fibrosis compared to the general population. The diagnosis is based on clinical, radiological, and microbiological criteria. Unfortunately, the first two criteria lack specificity, and microbiological detection of NTM is limited due to frequent sputum contamination by other pathogens in cystic fibrosis patients. Given these factors and the high incidence of NTM infections in this population, alternative diagnostic methods are necessary.

Aim: This study aims to validate an innovative diagnostic test based on the IGRA (Interferon-Gamma Release Assay) method, which measures T lymphocyte response to Interferon gamma (IFNγ). The test will be conducted on a subset of patients selected from the CIMeNT cohort (ID-RCB: 2017-A00025-48). This cohort consists of cystic fibrosis patients whose NTM infection prevalence has been previously assessed.

Method: This research is a multicenter case-control study. It includes two groups: a case group of patients with positive serological and/or microbiological responses indicating NTM infection, and a control group of patients without such responses. The test measures the host's immune response by evaluating circulating T cell activity. Specifically, it measures IFNγ release when T cells are in contact with NTM antigens. This method provides more informative diagnostics of NTM infection dynamics compared to serology or microbiology, which have known technical limitations.

The study involves a single visit, which is part of the routine care for cystic fibrosis patients. During this visit, a routine blood draw will be performed and an additional 7 ml tube will be collected.

Inclusion criteria

• Patient ≥18 years
• Patient previously included in the CIMeNT study
• Patient with a confirmed diagnosis of cystic fibrosis regardless of CFTR genotype
• Patient affiliated to the social security system
• Patient registered in the French Cystic Fibrosis Registry
• Adult patient capable of spontaneous expectoration or after induction

Exclusion criteria

• Lung transplant patients
• Person placed under judicial protection
• Pregnant and breastfeeding women