Blood Culture Collection Strategies for Suspected Bloodstream Infection

Blood cultures are the reference standard for diagnosing bloodstream infections and are essential for the management of patients with suspected sepsis. Their diagnostic performance depends strongly on the total volume of blood collected, while each additional venipuncture may increase patient discomfort, staff workload, and the opportunity for contamination.

This prospective diagnostic study will evaluate two blood culture collection strategies within the same adult participant. Consecutive patients with a clinical indication for blood culture collection will be enrolled at Izola General Hospital. During the initial venipuncture, two complete blood culture sets, consisting of two aerobic and two anaerobic bottles and approximately 40 mL of blood, will be collected. One additional set, consisting of one aerobic and one anaerobic bottle and approximately 20 mL of blood, will then be collected from a second venipuncture site during the same diagnostic episode, generally within 30-60 minutes according to routine clinical workflow.

The diagnostic performance of the single-venipuncture strategy will be determined from the initial four bottles. The diagnostic performance of the sequential two-venipuncture strategy will be determined from all six bottles. Each participant will therefore serve as their own control. The primary outcome is the paired difference in detection of clinically significant bloodstream pathogens. Secondary outcomes include the incremental diagnostic yield of the additional set, contamination, overall positivity, time to positivity, and the distribution of pathogens and contaminants.

The investigators hypothesize that the single-venipuncture strategy will identify most clinically significant bloodstream pathogens detected by the complete protocol, while the additional set will provide a measurable but limited incremental diagnostic yield.