From the Guidelines
A left shift on a CBC with differential refers to an increase in immature neutrophils (band cells) in the blood, not simply an elevated WBC and neutrophil count. This occurs when the bone marrow releases immature neutrophils into circulation before they fully mature, typically in response to acute bacterial infections, as suggested by the Infectious Diseases Society of America guidelines 1. The term "left shift" comes from the traditional manual differential count layout, where immature cells appear on the left side of the reporting sheet. This finding indicates that the body's demand for neutrophils exceeds the supply of mature cells, forcing the release of immature forms to fight infection. Common causes include:
- Bacterial infections
- Inflammation
- Tissue damage
- Certain medications
- Some cancers A left shift is clinically significant as it suggests an active inflammatory process requiring prompt evaluation, especially when accompanied by symptoms of infection, as recommended by the clinical practice guidelines for the evaluation of fever and infection in older adult residents of long-term care facilities 1. The degree of left shift can sometimes correlate with infection severity, though this must be interpreted alongside other clinical findings and laboratory values, such as the presence of an elevated WBC count or a left shift, which warrants a careful assessment for bacterial infection in any resident with suspected infection, with or without fever 1.
From the Research
CBC with Differential and Left Shift
- A CBC (Complete Blood Count) with differential is a laboratory test that measures various components of the blood, including white blood cell (WBC) count and differential [ 2 ].
- When the WBC count is elevated and neutrophils are elevated, it is called a left shift [ 2 ].
- A left shift indicates an increase in neutrophil consumption that is equal to an increase in production, suggesting a possible bacterial infection [ 2 ].
Meaning of Left Shift
- Left shift does not occur in the extremely early or late phases of infection, making it essential to assess time-series data of left shift and WBC count to evaluate patient condition [ 2 ].
- A change in left shift and WBC count can reflect real-time neutrophil consumption during the course of a bacterial infection, allowing for more accurate evaluation of patient condition [ 2 ].
- Interpreting abnormal CBC results, including left shift, requires a structured approach to diagnose and manage underlying conditions [ 3 ].
Clinical Usage of CBC
- The complete blood count is one of the most frequently ordered laboratory tests in medicine, providing valuable information about various cell components [ 4 ].
- Understanding the components of the CBC, including the WBC count and differential, is essential for difficult diagnoses and monitoring treatments for hematologic disorders and other medical problems [ 4 ].
- Nurses can use the information from the CBC to inform their plan of care and produce the best patient outcomes [ 5 ].