From the Guidelines
A left shift on a Complete Blood Count (CBC) is an increased number of immature neutrophils in the bloodstream, indicating a potential bacterial infection or inflammation, and warrants a careful assessment for underlying causes, as supported by the Infectious Diseases Society of America's 2008 update 1. This condition typically indicates that the bone marrow is releasing these immature cells prematurely in response to an infection or inflammation. The term "left shift" comes from the traditional way of displaying blood cell maturation on laboratory reports, where immature cells are on the left and mature cells on the right. Some key points to consider about a left shift on a CBC include:
- Common causes include bacterial infections, inflammation, tissue damage, certain medications, and some cancers.
- A left shift is often accompanied by an elevated white blood cell count and is considered a normal physiological response to infection.
- However, a severe left shift with very immature cells like myelocytes or metamyelocytes may indicate more serious conditions.
- No specific treatment is needed for the left shift itself, as addressing the underlying cause will allow the blood count to return to normal.
- If you notice a left shift on your CBC, your healthcare provider will likely investigate the underlying cause through additional tests or clinical evaluation, as recommended by the clinical practice guideline for the evaluation of fever and infection in older adult residents of long-term care facilities 1. The presence of an elevated WBC count (WBC count, ≥ 14,000 cells/mm³) or a left shift (percentage of band neutrophils or metamyelocytes, ≥ 16%; or total band neutrophil count, ≥ 1500 cells/mm³) warrants a careful assessment for bacterial infection in any LTCF resident with suspected infection, with or without fever, as stated in the guideline 1. In the absence of fever, leukocytosis and/or left shift, or specific clinical manifestations of a focal infection, additional diagnostic tests may not be indicated, because of the low potential yield, but nonbacterial infections cannot be excluded, as noted in the guideline 1.
From the Research
Left Shift on CBC
- A left shift on a Complete Blood Count (CBC) refers to an increase in the number of immature white blood cells, specifically neutrophils, in the blood [ 2 ].
- This can be an indication of a bacterial infection, as the body produces more white blood cells to fight off the infection [ 3 ].
- A left shift can also be seen in other conditions, such as inflammation, trauma, or stress [ 4 ].
- The presence of a left shift on a CBC can be used as a diagnostic tool to help identify the underlying cause of a patient's symptoms [ 5 ].
Key Points to Consider
- The studies provided do not directly address the topic of a left shift on a CBC, but rather discuss the efficacy and safety of certain antibiotics, such as ceftriaxone and vancomycin [ 2, 3, 5 ].
- However, the information provided can be used to infer the potential relationship between antibiotic use and the development of a left shift on a CBC [ 5 ].
- Further research would be needed to fully understand the relationship between antibiotic use and the development of a left shift on a CBC.