Bloodstream infections are a common clinical concern with a high mortality rate. At present, many hospitals still lag significantly behind advanced institutions in Europe and North America in the area of blood culture testing. Several factors hinder the widespread implementation of blood cultures, the most critical being the high cost of specimen submission and the lack of standardized specimen collection procedures. Therefore, it is imperative to promptly establish reasonable, nationally appropriate fee schedules for blood culture testing and to standardize specimen‑collection practices.

Blood collection in the early stages of fever

Many factors influence the detection rate of blood cultures, including the timing of blood collection, the number of blood culture bottles used, and the volume of blood cultured. Studies have shown that, within 1 hour before the onset of chills or fever, Bacteria A large volume enters the bloodstream and is cleared 30 to 90 minutes after the peak of fever. Therefore, drawing blood during chills or in the early phase of fever can increase the positive rate of blood cultures. Specifically, the indications for blood culture collection are as follows:

1. Fever ≥38°C or hypothermia ≤36°C, accompanied by chills.

2. Leukocytosis (count > 10 × 10^9/L).

3. Neutropenia, with mature polymorphonuclear leukocytes <1 × 10^9/L.

4. Thrombocytopenia and cutaneous–mucosal bleeding.

5. Hypotension, coma, and multiple organ failure.

6. Rapid breathing, elevated procalcitonin (PCT), and increased C-reactive protein (CRP).

7. Before systematic antimicrobial therapy is initiated for critically ill patients admitted to the hospital. www.labdd.com

It’s best to perform double‑set cultivation.

As the number of blood culture bottles submitted increases, the detection rate of bloodstream infections rises accordingly. Reports indicate that submitting 1, 2, and 3 sets of blood cultures yields pathogen detection rates of 65.0%, 80.0%, and 96.0%, respectively. Based on these findings, the American Clinical… Laboratory The Institute of Standardization recommends performing dual or triple blood cultures simultaneously. Dual cultures involve drawing blood from two sites, ideally on the left and right arms; each set includes two bottles—one aerobic and one anaerobic. Using both types of bottles enhances the positive rate and allows for the isolation of a broader range of organisms, including staphylococci, streptococci, Enterobacteriaceae, and anaerobes. For adult patients, collecting only a single blood culture bottle is insufficient; inadequate volume and a single set may yield results that are difficult to interpret accurately. Repeated collections are not necessary during the subsequent 2 to 5 days.

For infective endocarditis, three sets of blood cultures should be collected at 30–60-minute intervals; monitoring should continue for 24 hours, and if the results are negative, two additional sets should be obtained. In adult patients, each set should contain 20–30 mL of blood. In infants and young children, the volume of blood drawn should not exceed 1% of the patient’s total blood volume.

Avoid blood contamination.

Contamination of blood cultures is a major obstacle to their clinical application. When contamination occurs, it can lead to false‑positive results, complicating treatment decisions. Studies have shown that when Staphylococcus aureus, Streptococcus pneumoniae, Escherichia coli and other Enterobacteriaceae, Pseudomonas aeruginosa, or Candida albicans are isolated from blood cultures, these findings are most often indicative of true bacteremia (>90.0%). In contrast, isolates belonging to the genera Corynebacterium, Bacillus, and Propionibacterium are rarely associated with true bacteremia (<5.0%). Among streptococci, enterococci, and coagulase‑negative staphylococci, the proportions attributable to true bacteremia are 38.0%, 78.0%, and 15.0%, respectively.

When collecting specimens, care should also be taken to draw venous blood using a disposable syringe and then transfer it into blood culture bottles, following the sequence of aerobic and anaerobic bottles. Directly drawing blood into the blood culture bottle is not recommended. It is advisable to use culture bottles containing a resin additive, as this can increase the positive rate.