WBC
Background
- White blood cell count; measure of circulating leukocytes
- Reported on CBC with differential (neutrophils, lymphocytes, monocytes, eosinophils, basophils)
Normal Values
- Normal: 4,500-11,000/mcL
- Leukocytosis: >11,000/mcL
- Leukopenia: <4,500/mcL
Interpretation
- Leukocytosis: infection (most common), stress response, steroids, leukemia, dehydration
- Left shift (increased bands/immature forms) suggests acute bacterial infection
- WBC >30,000 with blasts: consider leukemia
- Leukopenia: viral infections, medications (chemotherapy, antibiotics), bone marrow failure, sepsis (ominous sign)
- Neutropenia (ANC <500): high-risk for life-threatening infection; ANC = WBC x (% neutrophils + % bands)
- WBC is a poor predictor of serious bacterial infection in isolation; interpret in clinical context