Diagnosis of bloodstream infections in immunocompromised patients by real-time PCR

The diagnosis of bloodstream infections (BSIs) in immunocompromised patients, such as patients with cancer, is challenging. Although blood culture (BC) is considered the standard diagnostic tool for BSIs, it takes several days to yield results and has low sensitivity in these patients. Here, we tested a novel method for diagnosing BSIs in a large cohort of immunodepressed patients.

Real-time PCR (LightCycler SeptiFast Test M(GRADE), Roche Diagnostics) was compared with BC for its ability to detect bacteria and fungi in blood samples from 100 immunocompromised patients (98 with cancer) in whom sepsis was suspected.

In concordant samples (79.2% of total cases), real-time PCR identified the presence or absence of microbes significantly faster than BC (p=3.7x10(-49), t-test). Furthermore, in 6 cases, SeptiFast distinguished contamination of BCs by coagulase-negative staphylococci. SeptiFast, however, failed to detect 5 cases of clinically relevant BSI that tested positive by BC.

SeptiFast rapidly diagnosed BSIs in our cohort of immunosuppressed patients. The results of this study suggest that SeptiFast can be used in conjunction with, but cannot replace, BC to better identify the etiology of fever in immunocompromised patients.