Laboratory Evaluation for Neutropenia
For patients presenting with neutropenia, a comprehensive laboratory workup should include a complete blood count with differential, blood cultures, comprehensive metabolic panel, and chest radiography to determine the cause and guide management. 1, 2
Initial Laboratory Evaluation
Essential Tests (First Line)
- Complete blood count (CBC) with differential leukocyte count and platelet count 1
- Serum creatinine and blood urea nitrogen levels 1
- Electrolytes, hepatic transaminase enzymes, and total bilirubin 1
- Blood cultures (at least 2 sets):
- One set from each lumen of central venous catheter (if present)
- One set from peripheral vein
- For patients weighing <40 kg, limit blood culture volumes to <1% of total blood volume 1
Additional Tests Based on Clinical Presentation
- Chest radiograph for patients with respiratory signs or symptoms 1
- Culture specimens from other suspected infection sites (e.g., urine, sputum, skin lesions) 1
- Serum tryptase levels and vitamin B12 levels (to evaluate for myeloproliferative disorders) 1
- Peripheral blood smear to assess for other blood count abnormalities (dysplasia, monocytosis, circulating blasts) 1
Further Diagnostic Workup
For Persistent or Severe Neutropenia
- Bone marrow aspirate and biopsy with:
For Suspected Specific Etiologies
- Skin biopsy or aspiration of lesions for histological, cytological, and microbiological evaluation in immunocompromised patients 1
- Serologic testing for infectious causes (if clinically indicated) 1
- Antineutrophil cytoplasmic antibodies and antinuclear antibodies (if autoimmune neutropenia suspected) 1
- Quantitative serum immunoglobulin levels (including IgE) 1
- CT imaging of chest, sinuses, abdomen, or pelvis as clinically indicated 1
Risk Assessment
Risk stratification is crucial for determining management approach:
High-Risk Criteria
- Profound neutropenia (ANC <100 cells/mm³) expected to last >7 days 1
- MASCC score <21 1, 2
- Presence of comorbid conditions (hemodynamic instability, oral/GI mucositis, new pulmonary infiltrates) 1
Low-Risk Criteria
Monitoring Recommendations
- CBC monitoring at least every 3 days during intensive antibiotic therapy 1
- Weekly monitoring of serum transaminase levels for patients with complicated courses or suspected hepatic injury 1
- Daily clinical assessment of temperature trends, vital signs, and laboratory parameters 2
- Reassessment after 48-72 hours to determine need for treatment modification 2
Important Considerations
- Signs and symptoms of inflammation are often attenuated or absent in neutropenic patients 1
- Serum markers of inflammation (C-reactive protein, interleukins-6 and -8, procalcitonin) have shown inconsistent results and are not routinely recommended 1
- Afebrile neutropenic patients with new signs or symptoms of infection should be evaluated and treated as high-risk patients 1
- Early involvement of infectious disease specialists may improve outcomes in complicated cases 1
By following this systematic laboratory approach, clinicians can effectively diagnose the cause of neutropenia and implement appropriate management strategies to reduce morbidity and mortality in affected patients.