How is bandemia determined based on a Complete Blood Count (CBC)?

From the Guidelines

Bandemia is determined by the presence of a left shift, which is indicated by a percentage of band neutrophils or metamyelocytes of 16% or greater, or a total band neutrophil count of 1500 cells/mm³ or greater, as evidenced by a Complete Blood Count (CBC) with differential 1. To determine bandemia based on a CBC, it is essential to examine the differential cell count, specifically looking for the percentage of band neutrophils or the absolute band neutrophil count.

• A manual differential is preferred to assess bands and other immature forms, as automated CBC machines may not provide this specific information 1.
• The presence of an elevated white blood cell (WBC) count, defined as 14,000 cells/mm³ or greater, in combination with a left shift, warrants a careful assessment for bacterial infection 1.
• Bandemia is a significant finding, as it often indicates an active infection or inflammatory process, prompting the bone marrow to release immature neutrophils into circulation to combat the infection. Key points to consider when reviewing CBC results for bandemia include:
• The percentage of band neutrophils or metamyelocytes, with 16% or greater being indicative of a left shift 1
• The total band neutrophil count, with 1500 cells/mm³ or greater being considered abnormal 1
• The clinical context, including the presence of fever, symptoms of infection, or other laboratory findings, to guide the interpretation of CBC results and the determination of bandemia 1.

From the Research

Determining Bandemia based on CBC

To determine bandemia based on a Complete Blood Count (CBC), several studies have provided insights into the relationship between band percentages and the likelihood of bloodstream infections and in-hospital mortality.

• Bandemia is generally defined as a band count greater than 10% of the total white blood cell count 2.
• However, some studies suggest that even lower percentages of bands can be associated with an increased risk of bloodstream infections and in-hospital mortality 3, 4.
• The percentage of bands can be grouped into different categories, such as zero (0% bands), minimal (1-2% bands), mild (3-4% bands), moderate (5-10% bands), and high (>10% bands) 3.
• Increasing rates of bloodstream infections and in-hospital mortality have been observed as band percentages increase from zero to high 3.
• Some studies have also found that bandemia is associated with an increased risk of positive cultures, including blood cultures, and in-hospital mortality, even in patients with normal total white blood cell counts 4.

Clinical Significance of Bandemia

The clinical significance of bandemia can vary depending on the patient population and the underlying condition.

• In some cases, bandemia may be associated with an increased risk of adverse events, such as bloodstream infections and in-hospital mortality 3, 4, 2.
• However, other studies have found that severe bandemia is not associated with an increased risk of adverse events in certain patient populations, such as pediatric patients 5.
• Clinicians should consider the overall context of the patient's history, physical examination, and other laboratory and imaging data when interpreting the results of a CBC and determining the clinical significance of bandemia 5.

Diagnostic Criteria for Bandemia

The diagnostic criteria for bandemia can vary depending on the study and the patient population.

• Some studies have used a cutoff of >10% bands to define bandemia 3, 2.
• Other studies have used different cutoffs, such as >5% bands or >20% bands 4, 5.
• The choice of diagnostic criteria may depend on the specific patient population and the clinical context in which the CBC is being performed.