Evaluation of RT-PCR compared to Galactomannan and 1,3-β-D-glucan test in serum for early and specific diagnosis of invasive aspergillosis in hematologic patients.

Invasive fungal infections (IFI) are an increasing problem in Intensive Care Units (ICUs) due to the increase in the number of patients at risk. The mortality attributable to these infections is high and conventional diagnostic methods are not always fast and reliable. Conventional diagnostics is based on cultural methods but these suffer of a very low limit of detection being hematological patients prophylaxed by antifungal drugs: the pharmacological treatment inhibits pathogens growth in vitro leading to false negative results. Peculiar immunosuppression of these patients affects indirect assays based on specific antibodies. It is also advisable to use too invasive respiratory samples collection techniques such as bronchoalveolar lavage (BAL). The dosage of fungal antigens in serum and other samples is a non-invasive technique, but not always satisfying in terms of timing and diagnostic confidence. The aim of this study is to standardize a new molecular assay, based on Real Time-polymerase chain reaction (RT-PCR), in order to associate it to these antigenic assays, for a more complete and earlier diagnosis of invasive fungal infections in onco-hematological patients. For this purpose, the only three commercial kits certified for diagnosis have been compared on serum samples. For each amplification kit, its manufacturer suggests a proper DNA extraction method: all methods were evaluated to test their effectiveness. According to the EORTC/MSG criteria, the population was divided into patients with proven, probable, possible or absent invasive fungal infection. Sensitivity and specificity of the antigen tests were calculated by comparing these groups. An eventual correlation was evaluated also among groups presenting different antigenic pattern of BG and GM serum antigens.