What is the likely cause and recommended work‑up for a patient with a total white blood cell count of 11.4 ×10⁹/L, absolute neutrophil count of 10.10 ×10⁹/L, and absolute lymphocyte count of 0.80 ×10⁹/L?

Evaluation of Neutrophilia with Lymphopenia

Your laboratory values show a stress-induced neutrophilia with relative lymphopenia, most likely representing a physiologic response to acute infection, inflammation, or physical stress rather than a primary hematologic disorder. 1, 2

Understanding Your Laboratory Results

Your complete blood count shows:

• WBC 11.4 × 10⁹/L: Mildly elevated but within the normal range for hospitalized patients (reference range 1.6-14.5 × 10⁹/L) 3
• Absolute neutrophil count 10.10 × 10⁹/L: Elevated (neutrophilia), indicating an active immune response 1
• Absolute lymphocyte count 0.80 × 10⁹/L: Low (lymphopenia), which commonly accompanies acute stress or infection 2, 4

The neutrophil-to-lymphocyte ratio in your case is approximately 12.6, which indicates significant physiologic stress or systemic inflammation. 2

Most Likely Causes

Primary Considerations

• Acute bacterial infection: The combination of neutrophilia and lymphopenia is highly predictive of bacteremia and should prompt evaluation for infection sources 4
• Physical or emotional stress: Seizures, anesthesia, overexertion, or emotional stress can elevate neutrophil counts while suppressing lymphocytes 1, 2
• Viral infections: Common respiratory viruses can cause this pattern, particularly in the context of secondary bacterial infection 5
• Medications: Corticosteroids, lithium, and beta-agonists commonly cause leukocytosis with neutrophilia 1

Less Common but Important Causes

• Inflammatory conditions: Systemic inflammation from any cause produces this white blood cell pattern 2
• Recent surgery or trauma: Major surgical stress characteristically produces marked neutrophilia (up to 84.4%) and lymphopenia (down to 10.3%) 2

Recommended Diagnostic Work-Up

Immediate Assessment

• Obtain a comprehensive metabolic panel including BUN, creatinine, electrolytes, calcium, albumin, and LDH to assess for infection complications or organ dysfunction 6
• Blood cultures before any antibiotics if fever is present (temperature >38°C/100.4°F) or if bacteremia is suspected 5, 6
• Review all current medications for drugs that can cause leukocytosis, particularly corticosteroids, lithium, and beta-agonists 1
• Assess for infection sources: Perform targeted cultures (urine, sputum, wound) based on clinical symptoms 5

Clinical Red Flags Requiring Further Investigation

Proceed to bone marrow evaluation if any of the following are present: 6, 7

• Progressive decline in WBC counts on serial testing
• Concurrent anemia or thrombocytopenia
• Presence of immature cells (blasts) on peripheral smear
• Unexplained weight loss, night sweats, or lymphadenopathy
• Splenomegaly or hepatomegaly
• WBC count >100 × 10⁹/L (medical emergency due to hyperviscosity risk) 1

Additional Testing if Counts Persist

• Peripheral blood flow cytometry to exclude chronic lymphocytic leukemia or other lymphoproliferative disorders, particularly if lymphopenia persists beyond the acute illness 7
• Viral serologies (HIV, EBV, CMV, influenza) if lymphopenia persists without clear cause 7

Management Approach

For Suspected Infection (Most Likely Scenario)

• Initiate broad-spectrum antibiotics immediately if fever is present with signs of systemic infection, after obtaining blood cultures 5, 6
• Monitor for fever precautions: Seek immediate care if temperature exceeds 38°C (100.4°F) 7
• Avoid invasive procedures until infection is controlled, as neutrophilia indicates active immune response 5

Monitoring Strategy

• Repeat CBC in 3-5 days to assess response to treatment and ensure normalization of counts 6, 7
• Weekly CBC monitoring is indicated if lymphopenia persists (ANC 1,000-1,500 cells/µL range) until counts stabilize 7
• Trending is more important than a single value: Serial measurements help distinguish physiologic stress response from pathologic processes 8

What This Pattern Does NOT Suggest

Your counts do NOT indicate: 6, 8

• Severe neutropenia requiring growth factor support (your ANC is elevated, not low)
• Immediate need for antimicrobial prophylaxis (neutrophil count is adequate for infection defense)
• Primary bone marrow failure (isolated mild abnormalities without other cytopenias)
• Chemotherapy-induced toxicity (unless you are receiving cytotoxic therapy)

Common Pitfalls to Avoid

• Don't ignore fever or signs of infection: The combination of neutrophilia and lymphopenia is more predictive of bacteremia than total WBC count alone 4
• Don't assume malignancy without other supporting features: Isolated neutrophilia with lymphopenia in the context of acute illness is usually reactive, not neoplastic 1
• Don't delay antibiotics if infection is suspected: Obtain cultures first, then treat empirically while awaiting results 5, 6
• Don't panic over mildly elevated WBC: Values between 11-14.5 × 10⁹/L represent normal variation in hospitalized patients 3

When to Escalate Care

Seek immediate medical attention if: 6, 1

• Fever develops (especially >38°C/100.4°F)
• New symptoms of infection appear (cough, dysuria, wound drainage)
• Unexplained bleeding or bruising occurs
• Extreme fatigue or weakness develops
• WBC rises above 20 × 10⁹/L on repeat testing