Does a left shift in a Complete Blood Count (CBC) refer to neutrophil (neut) percentage or absolute number?

From the Guidelines

A left shift in a CBC is determined by looking at the neutrophil percentage, specifically the percentage of band neutrophils, rather than the absolute neutrophil count. When evaluating for a left shift, laboratory professionals examine the differential count to determine the percentage of band neutrophils (immature forms) relative to the total white blood cell count. According to the study by the Infectious Diseases Society of America 1, an increase in the percentage of neutrophils and band forms is a significant indicator of infection. Normally, band neutrophils make up less than 10% of total neutrophils, so an elevation above this threshold indicates a left shift. This finding is clinically significant because it suggests that the bone marrow is releasing immature neutrophils in response to an acute infection or inflammation, as the demand for neutrophils exceeds the supply of mature cells. Key points to consider when evaluating a left shift include:

• The percentage of band neutrophils is the primary indicator of a left shift
• A left shift can occur with or without an elevated total neutrophil count
• The presence of a left shift suggests an acute infection or inflammation
• Laboratory results should be discussed with the primary care clinician as soon as they are available, as noted in the study by the Infectious Diseases Society of America 1.

From the Research

Neutrophil Left Shift in CBC

A left shift in a Complete Blood Count (CBC) is an indication of an increased number of immature neutrophils in the blood. This can be measured by looking at either the neutrophil percentage or the absolute neutrophil count.

• The neutrophil left shift is often used as an indicator of infection or inflammation in the body 2, 3.
• The left shift can be measured by looking at the band count, which is the number of immature neutrophils in the blood 2.
• The absolute neutrophil count can also be used to measure the left shift, with an increase in the count indicating an increase in neutrophil production 3.
• The neutrophil percentage can also be used to measure the left shift, with an increase in the percentage indicating an increase in neutrophil production 4.

Measurement of Neutrophil Left Shift

The measurement of neutrophil left shift can be done using various methods, including:

• Manual differential count, which involves counting the number of immature neutrophils in a blood sample 2.
• Automated hematologic analyzers, which can measure the left shift by detecting the presence of immature neutrophils in the blood 2, 4.
• Flow cytometry, which can measure the expression of CD16 on neutrophils, which is decreased in immature neutrophils 4.

Clinical Significance of Neutrophil Left Shift

The neutrophil left shift has clinical significance in the diagnosis and management of various conditions, including:

• Bacterial infections, where a left shift can indicate an increase in neutrophil consumption 3.
• Inflammatory diseases, where a left shift can indicate an increase in neutrophil production 2.
• Fever with thrombocytopenia syndrome, where a left shift can be used as a predictor of severe disease 5.