The Role of Quantitative Real-Time PCR in the Invasive Pulmonary Aspergillosis Diagnosis: A Retrospective Study

Invasive pulmonary aspergillosis (IPA) reports significant mortality rates among critically ill patients. A prompt microbiological diagnosis is essential to establish a coherent antifungal treatment. Despite its low sensitivity and prolonged turn-around time, culture represents the conventional diagnostic technique. Additionally, galactomannan detection may support the diagnostic process. Ultimate generation methods, such as the real-time polymerase chain reaction (Real-Time PCR), integrated the diagnostic procedure to improve the overall laboratory effectiveness, especially regarding a quantitative Aspergillus spp. DNA detection. Herein, we propose a retrospective analysis where a quantitative real-time PCR was performed on respiratory samples belonging to patients with or without probable pulmonary aspergillosis. The study enrolled 62 samples, whose PCR results were compared to culture and galactomannan indexes. Additionally, clinical and general data were collected for all the patients. The qPCR assay reported 100% sensitivity and negative predictive value, while specificity reached 59.2% and the positive predictive value was 76.1%. Moreover, IPA patients reported fungal DNA loads higher than 103 in a logarithmic scale, while non-aspergillosis episodes reported a maximum level of 103. We hypothesized a future possibility to define a specific cut-off in distinguishing colonization from infection cases, requiring further investigations and speculations about IPA patients and respiratory samples.