What does the hematology workup reveal in a patient with Systemic Lupus Erythematosus (SLE)?

Hematological Workup in Patients with Systemic Lupus Erythematosus (SLE)

Patients with SLE commonly present with various hematological abnormalities that require specific testing and monitoring to guide treatment decisions and prevent morbidity and mortality.

Common Hematological Abnormalities in SLE

Anemia

• Most common hematological finding (56-86% of patients) 1, 2
• Types include:
  • Anemia of chronic disease (46% of cases) - most common 1
  • Autoimmune hemolytic anemia (AIHA) (28% of cases) 1
  • Iron deficiency anemia
  • Medication-induced anemia

Leukopenia and Lymphopenia

• Leukopenia (<4.0 × 10^9/L): 28-57% of patients 1, 2
• Lymphopenia (<1.5 × 10^9/L): 76-82% of patients (most common white cell abnormality) 1, 2
• Neutropenia (<1.8 × 10^9/L): 4.5-20% of patients 1, 2

Thrombocytopenia

• Prevalence: 17-40% of patients 1, 2
• Severity varies:
  • Mild (<150 × 10^9/L): 40% 1
  • Moderate (<100 × 10^9/L): 26% 1
  • Severe (<50 × 10^9/L): 8% 1

Antiphospholipid Syndrome (APS)

• Present in 10-15% of SLE patients at diagnosis 1, 2
• Associated with thrombotic events and pregnancy complications

Essential Hematological Workup

Basic Laboratory Tests

• Complete blood count (CBC) with differential
• Peripheral blood smear examination
• Reticulocyte count
• Direct Coombs test (for hemolytic anemia)
• Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP)
• Complement levels (C3, C4) - often decreased in active disease 1

Coagulation Studies

• Prothrombin time (PT)/International Normalized Ratio (INR)
• Activated partial thromboplastin time (aPTT)
• Fibrinogen levels - often elevated (35% of patients) 1

Immunological Tests

• Antiphospholipid antibodies:
  • Lupus anticoagulant (LA) testing 3
  • Anticardiolipin antibodies
  • Anti-β2 glycoprotein-I antibodies
• Anti-dsDNA antibodies - correlate with disease activity 1

Additional Testing When Indicated

• Bone marrow aspiration and biopsy:
  • Indicated for unexplained cytopenias
  • May show secondary dysplastic changes 4
  • Rules out other causes (malignancy, drug effects)
• Lupus anticoagulant testing protocol 3:
  • Dilute Russell's viper venom time (dRVVT) - first-line test
  • Sensitive aPTT - second-line test
  • Testing should be repeated >12 weeks after initial positive result

Interpretation of Hematological Findings

Disease-Related vs. Medication-Induced Cytopenias

• 83.4% of cytopenias are disease-related 2
• 16.6% are medication-related (azathioprine is most common cause) 2

Correlation with Disease Activity

• Patients with cytopenia at diagnosis often show:
  • Higher ESR
  • Lower C3 and C4 levels
  • Positive anti-dsDNA antibodies
  • Greater likelihood of renal involvement and APS 2

Special Considerations

• Lupus anticoagulant testing should be performed before starting anticoagulant therapy 3
• Testing for LA should be limited to patients with significant probability of APS or unexplained prolonged aPTT 3
• Bone marrow examination is necessary to rule out malignancy in cases of persistent unexplained cytopenia 4

Management of Hematological Manifestations

Hemolytic Anemia

• First-line: High-dose glucocorticoids 3
• For life-threatening cases or glucocorticoid failure: Rituximab 3

Thrombocytopenia

• First-line: High-dose glucocorticoids 3
• For severe cases (≤30 × 10^9/L):
  • Consider adding rituximab or intravenous immunoglobulin 3
  • Intravenous immunoglobulin has fewer side effects than rituximab 3

Antiphospholipid Syndrome

• Anticoagulation therapy for patients with thrombotic events 5
• For pregnant women with recurrent losses: Hydroxychloroquine + low-molecular-weight heparin + low-dose aspirin 5

Pitfalls to Avoid

• Failure to distinguish between disease-related and medication-induced cytopenias
• Overlooking the need for repeat testing for lupus anticoagulant (>12 weeks after initial positive result) 3
• Discontinuing hydroxychloroquine prematurely, which can lead to increased flares 5
• Inadequate monitoring of disease activity and medication toxicity
• Excessive glucocorticoid exposure, which can lead to metabolic complications 5

By understanding the hematological manifestations of SLE and implementing appropriate testing and management strategies, clinicians can reduce morbidity and mortality in these patients.