Diagnostic Study of Combined Biomnarker Testing in Bronchoalveolar Lavage Samples of Immunocompromised Patients

Overview

The aim of our prospective and multicentre diagnostic study is therefore to elucidate on the sensitivity and specificity rates of these serologic markers in combination with molecular tools (both an Aspergillus specific and a multifungal PCR based assay), as serologic mark-ers are not pathogen-specific, and furthermore to define species-specific cut-off values for BDG in BAL samples. Additionally, if genomic material of Aspergillus fumigatus is detected by PCR in a clinical sample, we investigate fungal DNA for point mutations in the cyp51A gene mediating resis-tance against common mould-active triazoles with novel rapid, sensitive and specific, non-culture-based PCR-assays and sequencing to optimize antifungal treatment as early as pos-sible.

The major problem in managing life threatening invasive fungal infections in patients (pts) with acute leukemia and pts after allogeneic hematopoietic stem cell transplantation is the lack of sensitive and specific diagnostic tools to identify fungal pathogens reliably and early in the course of the disease. Because of deep neutropenia and low platelet count, invasive diagnostic procedures are rarely feasible in time, therefore bronchoscopy with BAL is the method of choice in diagnosing pulmonary infections, as the sensitivity of culture-based methods from blood is low, especially in mould infections. Indirect methods, so-called surrogate markers, are becoming increasingly important in this clinical setting. These serologic markers, mainly galactomannan (GM) and recently 1(1,3)-β-D-glucan (BDG), have been validated in clinical trials for blood samples, however the clinical significance of testing BAL samples is up to now only based on retrospective data for GM and has not been reported yet for BDG. The aim of our prospective and multicentre diagnostic study is therefore to elucidate on the sensitivity and specificity rates of these serologic markers in combination with molecular tools (both an Aspergillus specific and a multifungal PCR based assay), as serologic markers are not pathogen-specific, and furthermore to define species-specific cut-off values for BDG in BAL samples. Additionally, if genomic material of Aspergillus fumigatus is detected by PCR in a clinical sample, we investigate fungal DNA for point mutations in the cyp51A gene mediating resistance against common mould-active triazoles with novel rapid, sensitive and specific, non-culture-based PCR-assays and sequencing to optimize antifungal treatment as early as possible. This study aims to improve the early, sensitive and specific diagnosis of invasive pulmonary fungal infections and detect azole resistance patterns, it might impact on the prognosis in hematologic patients; therefore antifungal treatment data and clinical outcome will be recorded. Clinical samples (BAL and blood) from approximately 100 pts suffering from acute leukemia and pts after allogeneic stem cell transplantation with febrile neutropenia and lung infiltrates diagnosed in a chest CT scan suggestive for fungal infection will be investigated after pts's informed consent in a multicentre, prospective trial. Pts will undergo standardized diagnostic imaging and microbiological procedures for identification of the underlying infectious pathogen. BAL and blood samples will be tested additionally for GM, BDG and with a diagnostic nested Aspergillus PCR assay, a multifungal DNA-Microarray and an azole resistance PCR assay. The molecular assays were established by our group and encompass the detection of Aspergillus fumigatus, Aspergillus flavus, Aspergillus terreus, Candida albicans, Candida dubliniensis, Candida glabrata, Candida lusitaniae, Candida tropicalis, Fusarium oxysporum, Fusarium solani, Mucor racemosus, Rhizopus microsporus, Scedosporium prolificans, Trichosporon asahii and identify the three most common point mutations that confer resistance to triazoles like voriconazole or posaconazole. Results of other diagnostic means including culture findings as well as patients' clinical data (e.g. duration of neutropenia, underlying disease and outcome including follow-up data concerning antifungal treatment and mortality attributable to fungal infections) will be documented, pseudonomyzed and included in our data bank. BAL and blood aliquots of 20 control pts without immunosuppression (suffering from lung diseases) will be collected and tested identically. Case definitions will be made according to 2008 EORTC/MSG criteria. The duration of the study will be approximately 24 months