Molecular diagnosis of sepsis in neutropenic patients with haematological malignancies

The rapid diagnosis of an infectious cause in the course of fever of unknown origin plays a pivotal role in the correct management of neutropenic patients. In this study, blood samples from febrile oncolhaematological patients were tested using a novel commercial real-time PCR assay (LightCycler SeptiFast; Roche Molecular Systems) and blood culture (BacT/Alert 3D; bioMerieux). Twenty-one (20.4%) and 34 (33%) of the 103 samples under study tested positive by blood culture and PCR, respectively. The analysis of concordance evidenced a low correlation between the two approaches (83%), mainly due to samples that tested negative by culture but positive using the molecular approach. Among 14 discordant cases negative by culture but positive by PCR, 12 were observed in sequential samples of patients with initial concordant results on samples drawn before the administration of a specific antimicrobial therapy. Moreover, DNA of a fastidious organism, Aspergillus fumigatus, not easily detectable by the cultural approach was rapidly detected in the two remaining discordant cases. Overall, the characteristics featured by the molecular method could be of interest in the development of new algorithms for the diagnosis of sepsis in critical patients.