What is the initial workup for a patient presenting with neutropenia?

Initial Workup for Neutropenia

The initial workup for a patient presenting with neutropenia should include a thorough history focusing on medication use and recent infections, complete blood count with differential, blood cultures, comprehensive metabolic panel, and chest radiography for those with respiratory symptoms. 1, 2

Definition and Risk Assessment

• Neutropenia is defined as an absolute neutrophil count (ANC) <1500 cells/μL, with severe neutropenia defined as ANC <500 cells/μL 1, 3
• Risk stratification is essential, with high-risk patients having anticipated prolonged (>7 days) and profound neutropenia (ANC <100 cells/μL) or a MASCC score <21 4, 1
• Low-risk patients have anticipated brief (<7 days) periods of neutropenia and few comorbidities or a MASCC score ≥21 4, 1

Initial Clinical Evaluation

• Examine sites most commonly infected in neutropenic patients: periodontium, pharynx, lower esophagus, lung, perineum, eyes, and skin 1, 5
• Evaluate all skin lesions, no matter how small, as signs of inflammation may be diminished in neutropenic patients 4, 1
• Assess for fever (≥38.3°C), which requires immediate intervention 1, 5
• Determine if this is the patient's initial episode of neutropenia or a recurrent episode 4

Laboratory and Diagnostic Testing

• Obtain at least 2 sets of blood cultures (from central venous catheter if present and peripheral vein) 1, 2
• Complete blood count with differential to confirm neutropenia and examine blood smear 6, 3
• Comprehensive metabolic panel including liver function tests, blood urea nitrogen, and creatinine 1, 2
• Urinalysis and urine culture if symptoms suggest urinary tract infection 2, 5
• For skin and soft tissue lesions, perform aspiration and/or biopsy for cytological/histological assessment, microbial staining, and cultures 4, 1
• Chest radiography for patients with respiratory signs/symptoms 1, 2
• Consider bone marrow examination with cytogenetics for unexplained or severe chronic neutropenia 6, 7

Additional Testing Based on Clinical Presentation

• For febrile neutropenia, determine the extent of infection through physical examination, blood cultures, chest radiograph, and additional imaging as indicated by clinical signs and symptoms 4, 1
• Consider CT imaging of chest and sinuses in high-risk patients to assess for occult invasive fungal infection 4, 1
• For patients with abdominal symptoms, consider abdominal CT to evaluate for neutropenic enterocolitis 4

Classification of Neutropenia

• Neutropenia can be classified as:
  • Mild (ANC 1000-1500/mm³), moderate (ANC 500-1000/mm³), or severe (ANC <500/mm³) 2, 3
  • Acute (evolving over days) or chronic (lasting >3 months) 8
  • Extrinsic (secondary to causes outside bone marrow) or intrinsic (primary bone marrow disorders) 3, 8

Management Considerations

• For febrile neutropenia, empiric broad-spectrum antibiotics should be initiated promptly 4, 1
• For high-risk patients, hospitalization and empiric antibacterial therapy with an antipseudomonal β-lactam such as cefepime, a carbapenem, or piperacillin-tazobactam is recommended 4, 2
• Early involvement of infectious diseases specialists, surgeons, and dermatologists familiar with neutropenic patients may improve outcomes 4, 1

Common Pitfalls to Avoid

• Delaying empirical antibiotic therapy in febrile neutropenic patients 1, 2
• Failing to obtain appropriate cultures before initiating antibiotics 1, 2
• Overlooking subtle signs of infection due to diminished inflammatory response 4, 1
• Not considering non-infectious causes of neutropenia such as medication effects 2, 3
• Inadequate blood culture volumes reducing diagnostic yield 2