From the Guidelines
A left shift in White Blood Cell (WBC) laboratory results indicates an increase in immature neutrophils, suggesting an active infection or inflammatory process, whereas a right shift shows predominantly mature neutrophils, often indicating vitamin deficiencies, chronic inflammation, or myeloproliferative disorders. When considering the difference between a left shift and a right shift, it's crucial to understand that these terms refer to changes in the distribution of neutrophils at different stages of maturity.
- A left shift is characterized by an increase in immature neutrophils (bands, metamyelocytes, myelocytes) in the peripheral blood, which suggests an active infection or inflammatory process where the bone marrow is releasing immature cells to meet increased demand, as seen in acute bacterial infections, severe inflammation, or tissue damage 1.
- A right shift, on the other hand, shows predominantly mature neutrophils with hypersegmented nuclei (more than 5 lobes), often indicating certain vitamin deficiencies (particularly B12 or folate), chronic inflammation, or myeloproliferative disorders. The terminology comes from the traditional way of recording neutrophil maturation on laboratory forms, with immature forms on the left and mature forms on the right. When interpreting these shifts, clinicians should consider them alongside the total WBC count and clinical presentation to determine appropriate treatment, such as investigating for nutritional deficiencies in the case of a right shift or considering antibiotics for a left shift with elevated WBC, as studies have shown that leukocytosis with a high percentage of neutrophils or left shift can indicate a high probability of an underlying bacterial infection 1.
From the Research
White Blood Cell (WBC) Shifts
- A left shift in WBC laboratory results refers to an increase in the number of immature white blood cells, such as band cells, in the blood [ 2 ].
- This can be an indication of infection, inflammation, or other conditions that stimulate the bone marrow to produce more white blood cells [ 3 ].
- A right shift, on the other hand, is not a commonly used term in the context of WBC laboratory results, but it can refer to an increase in the number of mature white blood cells, such as segmented neutrophils [ 4 ].
Clinical Significance
- The presence of a left shift can be a useful indicator of bacterial infection, as it reflects an increase in neutrophil consumption and production [ 5 ].
- However, a left shift can also be seen in other conditions, such as physical or emotional stress, and in response to certain medications [ 3 ].
- The combination of WBC count and left shift can provide a more accurate evaluation of patient condition, particularly in the context of bacterial infection [ 4 ].
Laboratory Evaluation
- WBC count and left shift are routine laboratory tests used to assess neutrophil state [ 2 ].
- Automated hematologic analyzers can provide left-shift flags, which can be useful in identifying patients with infection or inflammation [ 2 ].
- However, the diagnostic value of left-shift parameters is limited, and should be interpreted in conjunction with other laboratory and clinical findings [ 2 ].