Interpret this CBC (WBC 14.4 ×10⁹/L with neutrophilia 65.6% and lymphocytosis 27.4%, normal hemoglobin, hematocrit, platelets, MPV 12.5 fL) and advise immediate management.

CBC Interpretation: Mild Leukocytosis with Neutrophilia

This CBC shows mild leukocytosis (WBC 14.4 × 10⁹/L) with absolute neutrophilia (9.4 × 10⁹/L) most consistent with a reactive process—likely infection, inflammation, or physiologic stress—and does not require emergency intervention but warrants clinical correlation and possible further workup. 1, 2

Immediate Risk Stratification

This is NOT a medical emergency. The WBC count of 14.4 × 10⁹/L is well below the hyperleukocytosis threshold of >100 × 10⁹/L that would require immediate aggressive hydration, tumor lysis prophylaxis, and consideration of leukapheresis. 1, 3, 4

Key Reassuring Features:

• Normal hemoglobin (14.0 g/dL) and hematocrit (44.2%) exclude concurrent anemia that would raise concern for bone marrow pathology 5
• Normal platelet count (307 × 10⁹/L) argues against primary bone marrow disorders 4, 6
• No immature granulocytes (0.4%) or blasts on differential 7, 3
• No nucleated RBCs (NRBC 0.0%) excludes severe marrow stress or infiltration 7

Differential Diagnosis by Likelihood

Most Likely: Reactive Leukocytosis

The pattern of neutrophilia (65.6%) with absolute neutrophil count of 9.4 × 10⁹/L and normal lymphocyte percentage (27.4%) strongly suggests a reactive process. 7, 2

Common causes to evaluate:

• Bacterial infection: Left shift is minimal here, but absolute neutrophil count >9.0 × 10⁹/L increases likelihood of bacterial infection 1
• Inflammatory conditions: Inflammatory bowel disease, rheumatologic conditions 5
• Physiologic stress: Surgery, trauma, exercise, emotional stress can double WBC within hours 2, 4
• Medications: Corticosteroids, lithium, beta-agonists 4
• Smoking and obesity: Chronic mild elevation 2

Less Likely but Must Exclude: Hematologic Malignancy

Red flags that are ABSENT in this case:

• No blast cells on differential 3
• No left shift >16% bands (would increase likelihood ratio to 4.7 for serious pathology) 1
• No concurrent cytopenias 4, 6
• MPV is mildly elevated (12.5 fL) but platelet count is normal—this pattern can occur with inflammation or iron deficiency, not concerning for myeloproliferative disorder in isolation 8

Immediate Management Algorithm

Step 1: Clinical Correlation (Do Now)

Obtain focused history for:

• Fever, localizing infection symptoms, recent illness 7, 2
• Recent surgery, trauma, or physical/emotional stress 2, 4
• Current medications (especially corticosteroids, lithium) 4
• Constitutional symptoms: fever, night sweats, weight loss, fatigue, bruising (suggest malignancy) 2, 4
• Tick exposure or outdoor activities if febrile (consider ehrlichiosis/anaplasmosis) 7

Physical examination priorities:

• Splenomegaly or lymphadenopathy (requires immediate hematology referral) 1, 4
• Signs of infection or inflammation 2

Step 2: Peripheral Blood Smear Review

Order peripheral smear to evaluate for: 2, 6

• Blast cells or immature forms (would require same-day hematology referral) 3, 5
• Dysplastic features (suggest myelodysplasia) 7, 1
• Toxic granulations (support infection) 2
• Left shift quantification 1

Step 3: Additional Laboratory Testing Based on Clinical Context

If infection suspected:

• CRP and ESR to assess inflammatory activity 5
• Comprehensive metabolic panel 5
• Blood cultures if febrile 7
• Site-specific cultures as indicated 7

If no clear infectious/inflammatory cause identified:

• Repeat CBC in 1-2 weeks to assess persistence 2, 6
• If persistent leukocytosis without explanation, obtain: 6
  • Peripheral smear (if not already done)
  • LDH, uric acid (assess cell turnover) 3
  • Consider hematology referral

When to Refer to Hematology IMMEDIATELY

Absolute indications for same-day referral: 1, 3, 4

• Blast cells on peripheral smear
• Splenomegaly or lymphadenopathy on examination
• Concurrent unexplained cytopenias
• Constitutional symptoms (fever, weight loss, night sweats) without infectious source
• WBC >100 × 10⁹/L (medical emergency)

Critical Pitfalls to Avoid

• Do not assume normal WBC excludes serious infection: Left shift ≥16% bands or absolute band count ≥1,500/mm³ significantly increases infection likelihood even with normal total WBC 1
• Do not delay peripheral smear if any concern for malignancy: Automated differentials can miss blast cells 2, 6
• Do not ignore persistent leukocytosis: If WBC remains elevated >2-4 weeks without clear cause, hematology evaluation is warranted 2, 6
• Do not overlook medication-induced leukocytosis: Corticosteroids are a very common cause 4

Bottom Line for This Patient

Given the mild elevation (WBC 14.4 × 10⁹/L), normal hemoglobin/platelets, absence of blasts or left shift, and mildly elevated MPV in isolation, this most likely represents reactive leukocytosis from infection, inflammation, or physiologic stress. 2, 4 Correlate with clinical symptoms, obtain peripheral smear if any concerning features present, and repeat CBC in 1-2 weeks if no clear cause identified. 2, 6