Interest of Real-time Polymerase Chain Reaction (PCR) in the Diagnosis of Fungal Infections

Invasive fungal infections are a major cause of morbidity and mortality in immunocompromised patients. Among them, patients with hematological malignancies, neutropenic patients, human immunodeficiency virus infected patients, diabetics, solid organ transplanted patients and patients admitted in an intensive care unit are particularly at high risk.

The survival of these patients depends on early diagnosis and prompt appropriate antifungal treatment. The early diagnosis of these infections is difficult because of the lack of sensitive test methods, notably blood cultures. Its sensitivity is poor or close-zero for aspergillosis. In addition, the response time is several days. For these reasons, we decided to develop a real-time PCR (Polymerase Chain Reaction) assay on blood samples. It should allow rapid response to establish a positive or negative diagnosis of invasive fungal infection, it could contribute strongly to the decision of treating using antifungals, and it should monitor the effectiveness and the optimization of antifungal prescriptions.

Methods:

Our project is a multicentre prospective inter-regional collaborative work between Nice, Rennes and Toulouse Mycological and parasitological laboratories. Our objectives are: First, to validate an extraction method from blood infected by fungi species. The three laboratories will work together to determine the best extraction method, since there is no consensus method for the extraction of nucleic acids of fungal origin in the context of human infections. The numerous extraction techniques already used lead to differences in the PCR results. As a consequence, inter-laboratory comparisons are not easy. Secondly, we aim to develop three real-time PCR assays: A panfungal real-time PCR assay able to detect most fungal species responsible for human diseases; a real-time PCR assay targetting Candida albicans and one targeting Aspergillus fumigatus which are two clinically important pathogens. Then patient blood samples (classified according to EORTC consensus) will be collected during the study in order to evaluate and validate our method on clinical samples. Results will allow us to determine the sensitivity, specificity and reproducibility, negative and predictive values.

Objectives Overall, our work aims to evaluate the clinical impact of real-time PCR in the early diagnosis of invasive fungal infections and on the initiation or stopping of antifungal therapy. The economic impact resulting from the use of this method will be evaluated. Indeed, an excellent predictive negative value of a panfungal real-time PCR assay could warrant a decrease in the use of empirical antifungal therapy

Inclusion criteria

• Healthy subjects: Chosen healthy subjects are donors of the Blood transfusion centre of NICE
• Ill subjects:

• Medical examination compatible with inclusion to donate blood
• To sign lit consent
• Affiliation to the regime of French national health and pensions organization
• Patient as whom there is intention to deal by systematic antifongique, Criteria, linked to the guest, clinical and microbiological are defined

Exclusion criteria

• Minor or person over 18 under tutelage.
• Subjects deprived of freedom.
• Patients cancelling their consent.
• Patients violating the research protocol.