Sequential Time to Positivity as a Prognostic Indicator in Bacteremia.

BACKGROUND

We aimed to determine the factors associated with sequential blood culture time to positivity (STTP) and validate the previously defined time to positivity (TTP) ratio threshold of 1.5 in predicting adverse disease outcomes and mortality of bacteremia (SAB).

METHODS

We conducted an observational study of adult patients with SAB. The TTP ratio was calculated by dividing the TTP of the second blood culture by that of the first.

RESULTS

Of 186 patients, 69 (37%) were female, with a mean age of 63.6 years. Median TTP was 12 hours (interquartile range [IQR], 10-15 hours) from the initial and 21 hours (17-29) from sequential blood cultures. Methicillin-resistant (MRSA)-infected patients had significantly shorter STTPs ( < .001) and lower TTP ratios ( < .001) compared to patients with methicillin-susceptible (MSSA). A significant correlation between initial and STTP was observed in patients with MRSA ( = 0.42, = .002) but not in those with MSSA. A higher rate of native valve endocarditis (NVE) significantly correlated with a TTP ratio of ≤1.5 (odds ratio, 2.65 [95% confidence interval, 1.3-5.6]; = .01). The subgroup having an initial TTP <12 hours combined with a TTP ratio ≤1.5 showed the highest prevalence of NVE.

CONCLUSIONS

The STTP varies based on methicillin susceptibility of isolate. This study suggests a potential clinical utility of the STTP to identify patients at a higher risk of NVE. However, prospective studies are required to validate these findings.