CBC Interpretation: Bacterial Infection Highly Likely
These results demonstrate leukocytosis with marked neutrophilia and lymphopenia, strongly suggesting an acute bacterial infection that requires immediate clinical evaluation and source identification.
Key Abnormalities
Your CBC shows three critical findings:
- Leukocytosis: WBC 14.74 ×10⁹/L (elevated above the 14.0 threshold)
- Neutrophilia: 85.4% neutrophils with absolute neutrophil count of 12.59 ×10⁹/L (markedly elevated)
- Lymphopenia: Absolute lymphocyte count 0.79 ×10⁹/L (significantly reduced)
Clinical Significance
The combination of WBC >14,000 cells/mm³ with neutrophil percentage >85% carries a likelihood ratio of 3.7-7.5 for documented bacterial infection 1. This pattern warrants urgent assessment for bacterial infection even in the absence of fever 1.
The neutrophil-to-lymphocyte ratio in this case is approximately 15.9 (12.59/0.79), which is markedly elevated and further supports acute bacterial infection 2.
Important Context
While the immature granulocyte percentage (0.5%) and absolute count (0.07) are within normal limits, their presence alongside leukocytosis still supports an infectious process. A true "left shift" (band forms ≥6% or absolute band count ≥1500) would have an even higher likelihood ratio of 14.5 for bacterial infection 1, but this requires manual differential counting to assess bands specifically.
Immediate Clinical Actions Required
Identify the infection source: Perform focused examination for:
- Respiratory symptoms (pneumonia is common with this pattern)
- Urinary symptoms or catheter presence
- Skin/soft tissue infections
- Abdominal pain or peritoneal signs
Obtain appropriate cultures before starting antibiotics:
- Blood cultures if fever, hypotension, or sepsis suspected
- Urine culture if urinary symptoms present
- Sputum culture if respiratory symptoms present
Consider empiric antibiotics if clinically indicated, particularly if the patient appears septic or has vital sign abnormalities
Additional Considerations
The RDW-CV (14.6) and RDW-SD (45.5) are at the upper limits of normal, which may suggest early anemia of inflammation or chronic disease, though this is a minor finding compared to the leukocytosis 3.
Common Pitfalls to Avoid
- Do not dismiss this as "stress leukocytosis" without thorough infection workup—the neutrophil predominance is too marked
- Do not wait for fever to initiate infection evaluation; older adults and immunocompromised patients may not mount febrile responses 1
- Do not attribute lymphopenia to viral infection in this context—the neutrophil predominance points to bacterial rather than viral etiology
- Be aware that certain populations (particularly those of African descent) may have lower baseline WBC counts 4, 5, but this patient's WBC is elevated regardless of ethnicity
In hospitalized patients, WBC counts between 11-14.5 may represent normal variation 6, but this patient's count of 14.74 exceeds even that expanded threshold, and the neutrophil predominance is the more concerning feature.