Interpret the complete blood count showing WBC (white blood cell count) 22.2 ×10⁹/L, neutrophils 80 % (segmented neutrophils) with absolute neutrophils 17.9 ×10⁹/L, hemoglobin 8.4 g/dL, hematocrit 27 %, MCV (mean corpuscular volume) 91.6 fL, RDW (red cell distribution width) 16.7 %, platelets 202 ×10⁹/L, MPV (mean platelet volume) 9.1 fL, immature granulocytes 0.9 % (absolute 0.2 ×10⁹/L), and nucleated red blood cells 0.2 ×10⁹/L?

Complete Blood Count Interpretation: Leukocytosis with Neutrophilia and Anemia

Primary Findings and Clinical Significance

This CBC demonstrates marked leukocytosis (WBC 22.2 ×10⁹/L) with severe neutrophilia (absolute neutrophils 17.9 ×10⁹/L, 80.6%), moderate normocytic anemia (hemoglobin 8.4 g/dL, MCV 91.6 fL), and the presence of nucleated red blood cells (0.2 ×10⁹/L), which collectively suggest either severe bacterial infection with stress erythropoiesis or a primary bone marrow disorder requiring urgent evaluation. 1, 2

Leukocytosis Analysis

Neutrophilia Assessment

• Absolute neutrophil count of 17.9 ×10⁹/L is markedly elevated and represents the most significant abnormality requiring immediate clinical correlation 1
• The neutrophil percentage of 80.6% has a likelihood ratio of 7.5 for bacterial infection 1
• Immature granulocytes at 0.9% (absolute 0.2 ×10⁹/L) indicates a left shift, which has a likelihood ratio of 4.7 for bacterial infection even when the percentage is below the 16% threshold 3, 1
• The absolute band count equivalent would be approximately 1,500 cells/mm³, which has the highest likelihood ratio (14.5) for documented bacterial infection 1

Differential Diagnosis for Leukocytosis

Bacterial infection is the most likely cause given the neutrophil predominance and left shift, with common sources including: 3, 1

• Respiratory tract infections (pneumonia)
• Urinary tract infections
• Skin and soft tissue infections
• Intra-abdominal infections

Alternative causes to consider: 1, 2

• Corticosteroid use (causes neutrophilic leukocytosis)
• Physical or emotional stress
• Lithium therapy
• Primary bone marrow disorders (less likely given platelet count is normal)

Anemia Evaluation

Red Blood Cell Parameters

• Hemoglobin 8.4 g/dL and hematocrit 27.1% represent moderate anemia requiring investigation 1
• MCV 91.6 fL indicates normocytic anemia, suggesting acute blood loss, hemolysis, chronic disease, or bone marrow suppression 1
• RDW 16.7% (elevated) suggests mixed red cell populations, which can occur with: 1
  • Early response to treatment (reticulocytosis)
  • Combined nutritional deficiencies
  • Recent transfusion

Nucleated Red Blood Cells (Critical Finding)

The presence of nucleated RBCs (0.2 ×10⁹/L) in peripheral blood is abnormal in adults and indicates: 4

• Severe hypoxia or tissue stress
• Bone marrow infiltration or dysfunction
• Severe hemolysis
• Sepsis or critical illness
• Possible myeloproliferative disorder

NRBCs in critically ill adults are associated with increased mortality and predict clinical deterioration, making this a red flag requiring urgent evaluation 4

Other Significant Findings

Monocyte and Eosinophil Elevation

• Monocytes absolute 1.3 ×10⁹/L (elevated) may suggest: 5
  • Chronic infection or inflammatory process
  • Recovery phase from acute infection
  • Tissue necrosis
• Eosinophils absolute 0.7 ×10⁹/L (elevated) is relatively minor but can occur with allergic reactions, parasitic infections, or drug reactions 2

Platelet Parameters

• Platelets 202 ×10⁹/L are normal, which argues against primary bone marrow failure or myeloproliferative neoplasm 6, 2
• MPV 9.1 fL (low) suggests decreased platelet production or consumption, though the platelet count remains adequate 3

Urgent Clinical Actions Required

Immediate Assessment

Within 12-24 hours, the following must be completed: 3, 1

1. Systematic infection evaluation:

   • Fever assessment and vital signs
   • Localizing symptoms (cough, dysuria, abdominal pain, skin lesions)
   • Signs of sepsis (hypotension, altered mental status, tachycardia)

2. Medication review:

   • Corticosteroids
   • Lithium
   • Beta-agonists
   • Recent chemotherapy

3. Physical examination focus:

   • Splenomegaly or hepatomegaly (suggests myeloproliferative disorder) 1, 6
   • Lymphadenopathy (suggests hematologic malignancy) 1
   • Signs of bleeding or bruising (suggests bone marrow dysfunction) 2

Laboratory Follow-up

If bacterial infection is suspected (most likely scenario): 3, 1

• Blood cultures (if fever, hypotension, or suspected bacteremia)
• Urinalysis and urine culture (if urinary symptoms)
• Chest radiograph (if respiratory symptoms or hypoxemia)
• Inflammatory markers (CRP, procalcitonin if available)

If infection is excluded or findings persist: 1, 6, 2

• Peripheral blood smear review by hematopathologist (to assess for dysplasia, blasts, or abnormal cells)
• Reticulocyte count (to assess bone marrow response to anemia)
• JAK2V617F mutation testing (if polycythemia vera suspected, though RBC count is low here)
• Hematology referral if constitutional symptoms, splenomegaly, or persistent unexplained findings

Critical Pitfalls to Avoid

Do not dismiss the nucleated RBCs as insignificant – their presence in adults indicates severe physiologic stress or bone marrow pathology and warrants urgent investigation 4

Do not assume normal platelet count excludes bone marrow disorder – early myeloproliferative neoplasms or myelodysplastic syndromes can present with isolated leukocytosis and anemia 6, 2

Do not delay empiric antibiotics if sepsis is suspected – the combination of marked neutrophilia with left shift and clinical instability requires immediate treatment while awaiting culture results 3, 1

Do not overlook medication-induced leukocytosis – corticosteroids are the most common cause of neutrophilia in hospitalized patients and can mask underlying infection 1, 2

Do not rely solely on automated differential – manual differential review is essential to accurately assess band forms, toxic granulation, and cellular morphology 1, 5

Most Likely Clinical Scenarios

Scenario 1 (Most Likely): Severe bacterial infection with anemia of inflammation 3, 1

• Marked neutrophilia with left shift strongly suggests bacterial infection
• NRBCs indicate severe physiologic stress
• Normocytic anemia consistent with acute inflammation or chronic disease
• Requires immediate infection workup and empiric antibiotics if clinically indicated

Scenario 2: Sepsis with bone marrow stress response 3, 4

• NRBCs in septic patients predict poor outcomes and ICU admission
• Anemia may reflect hemolysis, bleeding, or marrow suppression
• Requires aggressive resuscitation and source control

Scenario 3 (Less Likely): Primary bone marrow disorder 6, 2

• Normal platelets make acute leukemia or advanced myeloproliferative disorder less likely
• Would require peripheral smear review and hematology consultation
• Consider if no infectious source identified and findings persist