Diagnostic accuracy of SeptiFast multi-pathogen real-time PCR in the setting of suspected healthcare-associated bloodstream infection

SeptiFast is a real-time PCR assay which targets ribosomal DNA sequences of bacteria and fungi, enabling detection and identification of the commonest pathogens in blood within a few hours, including those acquired in healthcare settings. We report here the first detailed assessment of SeptiFast that focuses on healthcare-associated bloodstream infections which develop during routine critical care. This was a prospective multicentre study designed to compare the clinical diagnostic accuracy of SeptiFast versus microbiological culture and independent clinical adjudication. This Phase III diagnostic study was performed in an adequately sized cohort of adult patients who developed new signs of suspected bloodstream infection while receiving routine critical care. Of 1,006 new episodes of suspected bloodstream infection in 853 patients, 922 (92 %) of these episodes in 795 patients met the inclusion criteria of the study. Patients had been exposed to a median of 8 days (interquartile range 4-16) of hospital care and had received high levels of organ support and recent antibiotic exposure. The SeptiFast test, when compared with bloodstream infection at the species/genus level, had a greater specificity [0.86, 95 % confidence interval (CI) 0.83-0.88] than sensitivity (0.50, 95 % CI 0.39-0.61). There was a low prevalence of blood culture-proven pathogens (9.2 %, 95 % CI 7.4-11.2 %), and the post-test probabilities of both a positive (26.3 %, 95 % CI 19.8-33.7 %) and a negative SeptiFast test (5.6 %, 95 % CI 4.1-7.4 %) indicated potential limitations of this technology in diagnosing bloodstream infection. When compared with blood culture, SeptiFast is likely to have limited utility for the diagnosis of healthcare-associated bloodstream infection in critical care patients despite its potential to deliver results more rapidly.