From the Guidelines
A left shift is indicated by an increased percentage of band neutrophils, typically greater than 16%, in the total white blood cell count, as suggested by the most recent and highest quality study 1. This finding suggests that the bone marrow is releasing immature neutrophils into circulation before they fully mature, which commonly occurs in response to acute bacterial infections. During normal conditions, band neutrophils make up only about 3-5% of total neutrophils in peripheral blood. The presence of a left shift indicates that the body's demand for neutrophils exceeds the available supply of mature cells, prompting the release of these immature forms. This is part of the body's acute inflammatory response and is often accompanied by leukocytosis (elevated total white blood cell count). Some key points to consider when evaluating a left shift include:
- The percentage of band neutrophils is a critical factor in determining the presence of a left shift, with values greater than 16% being indicative of a left shift 1.
- The total white blood cell count, including the absolute neutrophil count, should also be considered when evaluating a left shift 1.
- A left shift can be an important indicator of bacterial infection, particularly in older adults or those with compromised immune systems 1.
- Monitoring the band count can help clinicians assess the severity of infection and response to treatment 1.
- It is essential to consider the clinical context and other laboratory results when interpreting a left shift, as it can be influenced by various factors, including the presence of fever, leukocytosis, or specific clinical manifestations of a focal infection 1.
From the Research
Lab Value Indicating a Left Shift
- A left shift is indicated by an increased percentage of band neutrophils in the total white blood cell count 2, 3, 4, 5.
- Specifically, a band count greater than 10% is often used as a clinical indicator of sepsis and can be useful in diagnosing infection 4.
- The combination of white blood cell count and left shift level can real-timely reflect the course of a bacterial infection, with different phases of infection characterized by changes in WBC count and left shift 5.
- An elevated band count can lead to a moderate increase in the likelihood of infection, while a negative test leads to only a small change in the posttest probability of infection 4.
Diagnostic Value of Lab Values
- The diagnostic value of absolute neutrophil count, band count, and morphologic changes of neutrophils in predicting bacterial infections has been evaluated, with band count being less sensitive than ANC and WBC count in predicting bacterial infections except in the elderly and infant population 3.
- Toxic granulation in neutrophils appears to be as sensitive as ANC in predicting bacterial infection 3.
- The odds ratio for infection was 8.67 for patients with a band count greater than 10%, indicating a significant association between elevated band count and infection 4.