Neutrophilia or Leukocytosis with Neutrophilia
When white blood cell count and neutrophils are both elevated, this is called neutrophilia (elevated neutrophils specifically) or leukocytosis with neutrophilia (elevated total WBC with predominant neutrophils). 1, 2
Terminology and Definitions
- Neutrophilia refers specifically to an elevated absolute neutrophil count (ANC) above the normal range (typically >6,700-7,000 cells/mm³) 1
- Leukocytosis refers to an elevated total white blood cell count (typically >11,000 cells/mm³) 1, 3
- When both are elevated together, the condition is most accurately described as leukocytosis with neutrophilia or simply neutrophilic leukocytosis 2, 3
Clinical Significance
The combination of elevated WBC and elevated neutrophils carries important diagnostic implications:
- Bacterial infection is the most common cause of this pattern, with specific likelihood ratios depending on the degree of elevation 1, 2
- A WBC count ≥14,000 cells/mm³ has a likelihood ratio of 3.7 for bacterial infection 1, 4
- An absolute band count ≥1,500 cells/mm³ carries the highest likelihood ratio (14.5) for documented bacterial infection 2, 4
- A neutrophil percentage >90% has a likelihood ratio of 7.5 for bacterial infection 2, 4
Associated Findings
When evaluating neutrophilia, clinicians should assess for:
- Left shift: An increase in immature neutrophil forms (bands ≥16%) with a likelihood ratio of 4.7 for bacterial infection 2, 5
- Toxic granulation: Morphologic changes in neutrophils that appear as sensitive as ANC in predicting bacterial infection 6
- Lymphocytopenia: A decrease in lymphocyte percentage often accompanies acute bacterial processes and helps distinguish bacterial from viral etiologies 1, 7
Important Clinical Caveat
Do not dismiss mildly elevated WBC counts (11-14 K/uL) when accompanied by high neutrophil percentage or elevated absolute neutrophil count, as these still indicate significant infection risk even without fever, particularly in elderly patients where 50% of documented bacterial infections present without fever 1, 2