Septifast PCR for the Microbiological Documentation of Infections in Febrile Neutropenic Patients

Frédéric Lamoth, Katia Jaton-Ogay, Thierry Calandra, Guy Prodhom, Laurence Senn, Jacques Bille, Oscar Marchetti.

Author address: 

Centre Hospitalier Universitaire Vaudois and University of Lausanne, Infectious Diseases Service and Microbiology Institute, Lausanne, Switzerland


Background: Blood cultures are the gold standard of microbiological diagnosis in febrile neutropenic patients. However, no causative agent is identified in 2/3 of febrile episodes. Septifast (Roche) is a new PCR test, which may detect bacterial and fungal DNA in blood (spectrum of 25 bloodstream pathogens). Objective: To assess the utility of Septifast PCR for the microbiological documentation of febrile neutropenia. Methods: Blood samples for blood cultures and Septifast PCR were prospectively drawn in 100 adult neutropenic cancer patients at D0 (onset of fever) and D3 (if persistent fever). Febrile episodes were classified as microbiologically (MDI) or clinically documented infection (CDI) and fever of unknown origin (FUO) according to the results of blood cultures. Results: 237 samples were analyzed in 146 febrile episodes (51 MDI, 51 CDI, 44 FUO). Blood cultures and Septifast were positive in 39 (27%) and 51 (35%) episodes, respectively. The pathogens were: i) blood cultures: Gram-positive 51%, Gram-negative 44%, mixed 5%, fungi 0%; ii) Septifast: Gram-positive 27%, Gram-negative 59%, mixed 8%, fungi 6%. Using blood cultures as reference, sensitivity of Septifast PCR was 38% (13% in Gram-positive, 57% in Gramnegative), specificity 64%, PPV 26%, NPV 76%. 39% of pathogens not detected by Septifast were not included in the test spectrum. Performance of blood cultures and Septifast PCR in different settings are shown in the table. Microbiological documentation was obtained by Septifast PCR in 29/98 (30%) blood culturenegative episodes: 19/51 (37%) CDI and 10/44 (23%) FUO. 19/23 (83%) pathogens identified by Septifast in CDI were consistent with the site of infection. Fungi were detected in 5 blood culturesnegative episodes of probable or possible invasive mycoses (Candida 4, Aspergillus 1). Conclusions: Septifast PCR is a promising additional tool for the microbiological documentation of blood culture-negative febrile neutropenic episodes. Septifast may be particularly useful in patients receiving antibiotics at time of blood sampling or with persistent fever.

abstract No: 


Full conference title: 

15th International Symposium on Infections in the Immunocompromised Host
    • ISIIH 15th