From the Guidelines
Significance of Leukocytosis in Infection
Leukocytosis, defined as a leukocyte count >14,000 cells/mm3, is a significant indicator of a potential underlying bacterial infection, particularly in older adults, with a likelihood ratio of 3.7 1.
Key Findings
- An elevated total band count (>1500 cells/mm3) has the highest likelihood ratio (14.5) for detecting documented bacterial infection 1.
- An increase in the percentage of neutrophils (>90%) and band neutrophils (16%, i.e., “left shift”) also had likelihood ratios of 7.5 and 4.7, respectively 1.
- The presence of leukocytosis, with or without fever, is associated with a high probability of an underlying bacterial infection in older persons 1.
Clinical Implications
In the context of diabetic foot infections, systemic symptoms such as feverishness and chills, marked leukocytosis, or major metabolic disturbances are uncommon but denote a more severe, potentially limb-threatening infection 1. In Clostridium difficile infection, leukocytosis with a white blood cell count of ≥15,000 cells/mL is a criterion for defining severe infection, and treatment guidelines recommend vancomycin or fidaxomicin for 10 days 1.
Conclusion is not allowed, so the response ends here.
From the Research
Significance of Leukocytosis
Leukocytosis, an elevation in white blood cell count, is a common laboratory finding that can be caused by various conditions, including infections, inflammatory processes, and primary bone marrow disorders 2, 3, 4. The significance of leukocytosis lies in its ability to indicate the presence of an underlying condition that requires medical attention.
Causes of Leukocytosis
The causes of leukocytosis can be broadly categorized into:
- Infections, such as bacterial or viral infections 3, 5
- Inflammatory conditions, such as chronic inflammatory diseases 4
- Primary bone marrow disorders, such as acute or chronic leukemias 2, 3, 4
- Physical or emotional stress 2, 3
- Medications, such as corticosteroids, lithium, or beta agonists 2
Clinical Implications
Leukocytosis can have significant clinical implications, including:
- Indicating the presence of a serious bacterial infection, particularly in febrile children 5
- Suggesting the presence of a primary bone marrow disorder, such as acute or chronic leukemia 2, 3, 4
- Requiring further evaluation and testing to determine the underlying cause 3, 6
- Guiding treatment decisions, such as the use of antibiotics or referral to a hematologist/oncologist 3, 4
Key Findings
Key findings related to leukocytosis include:
- Extreme leucocytosis (white blood cell count >25,000/mm^3) is associated with a higher risk of serious bacterial infections in febrile children 5
- Leukocytosis can be a sign of infection, particularly bacterial infection, and should prompt physicians to identify other signs and symptoms of infection 3
- A thorough history, physical examination, and peripheral blood smear are essential in evaluating patients with leukocytosis 4