Time to positivity of blood culture can predict different Candida species instead of pathogen concentration in candidemia

Abstract

The aim of this study was to systematically evaluate the predictive value of time to positivity (TTP) in candidemia. All first episodes of candidemic patients admitted to our hospital between January 2008 and July 2012 were recorded retrospectively. We analyzed the relationship between TTP, identification of Candida species, antifungal agent susceptibility, and patients' clinical characteristics (30-day mortality, underlying diseases, and associated risk factors). TTP of simulated blood culture with equal inoculum amounts of different Candida species was determined. We included 87 patients during the study period, with a mean TTP of 43.47 ± 19.51 h. TTP of C. glabrata was significantly longer (p < 0.001) and TTP of C. tropicalis was significantly shorter (p < 0.001) than that of other Candida species. Receiver operating characteristic (ROC) curve analysis showed that TTP can predict C. glabrata (with the cut-off value of >45.17 h) and C. tropicalis (with the cut-off value of ≤33.17 h) in candidemia with good sensitivity and specificity. No statistically significant relationship was found between TTP, antifungal agent susceptibility, and patients' clinical characteristics (p > 0.05). TTP was not a risk factor associated with mortality (p > 0.05). The TTP result in simulated blood culture was in accordance with that of the included patients. TTP has been demonstrated to be helpful to differentiate C. glabrata and C. tropicalis from other Candida species in candidemia, and it is not associated with antifungal agent susceptibility and patients' clinical characteristics. TTP cannot predict pathogen concentration in the blood of candidemic patients.