Validation of the Molecular Diagnosis of Respiratory Viral Infections on the Sputum of Patients With Cystic Fibrosis

Viral respiratory infections in cystic fibrosis (CF) have a significant impact on the progression of the disease. It is therefore essential to look for these viruses. No recommendations are made for the virological follow-up of CF patients and no optimal strategy for the type of sampling required. In non-CF patients, the search for a viral infection is performed by nasopharyngeal sampling. This method of sampling is invasive and uncomfortable for the patient. In CF patients, sputum, non-invasive sampling, is routinely used for bacterial research and may be used for viral infections to avoid invasive nasopharyngeal sampling in patients whose management is heavy.

After giving consent, both sputum and nasopharyngeal swab are collected for each participant. A record of clinical and biological data is also made at inclusion. A molecular viral search is performed on both samples by a multiplex technique detecting a broad spectrum of respiratory viruses. A bacteriological analysis is carried out on sputum. The molecular results will be interpreted blindly according to the main criterion of evaluation, presence or absence of viral infection.

Comparison of expectoration to nasopharyngeal sampling of CF patients for respiratory virological diagnosis should analyse agreement of the molecular viral detection and position CF sputum as an optimal assay for respiratory viruses with the advantage of not being invasive and in all cases routinely taken for the control and bacterial follow-up.

The promotion of sputum as an ad hoc sampling for viral research and epidemiology would facilitate the establishment of surveillance for viral infections in cystic fibrosis and thereby contribute to the CF register data.