How do steroids influence differential counts?

Effects of Steroids on Differential Blood Counts

Corticosteroids significantly alter differential blood counts, primarily causing increased neutrophils, decreased lymphocytes and eosinophils, with effects persisting for weeks after discontinuation. 1

Primary Effects on White Blood Cell Differential

Neutrophil Effects

• Corticosteroids cause a significant increase in neutrophil counts in peripheral blood
• After oral steroid administration, neutrophils increase by approximately 30-36% within the first month 1
• Neutrophil recruitment into airways increases specifically with oral corticosteroids but not with inhaled corticosteroids 2
• Mean increase in WBC count is approximately 2,400 cells/cu mm (range -600 to +8,000/cu mm) within 3 hours of oral steroid administration 3

Lymphocyte Effects

• Steroids cause a significant decrease in lymphocyte counts
• This contributes to an increased neutrophil-to-lymphocyte ratio (NLR) 4
• The decrease in lymphocytes occurs rapidly after steroid administration 3

Eosinophil Effects

• Corticosteroids consistently reduce sputum differential eosinophil counts (two- to sevenfold reduction) 5
• Blood eosinophil counts decrease by 30-36% within the first month of systemic corticosteroid therapy 1
• In patients with initial blood eosinophil counts ≥150, ≥300, and ≥400 cells/µL, mean reductions of 112,202, and 290 cells/µL respectively occur within one month 1

Time Course of Effects

• Effects begin within hours of administration (3 hours for significant WBC changes) 3
• Blood eosinophil counts remain decreased for several weeks after discontinuation of systemic corticosteroids 1
• Of patients with initial eosinophil counts ≥150 cells/µL who discontinued steroids within 7-21 days, 21-26% still had counts <150 cells/µL one month later 1
• The dose-response curve for inhaled corticosteroids on eosinophil reduction plateaus at low doses (equivalent to 200 μg/day beclomethasone) 5

Differences Between Administration Routes

• Oral corticosteroids increase airway neutrophils, while inhaled corticosteroids do not 2
• Both oral and inhaled corticosteroids decrease eosinophil counts 5, 2
• No significant differences in WBC response between daily and alternate-day steroid regimens 3

Clinical Implications

• The neutrophil-to-lymphocyte ratio (NLR) is an important marker that can predict response to steroid therapy in certain conditions 6, 4
• In community-acquired pneumonia, patients with high WBC count, high neutrophil count, or high NLR show more pronounced benefits from adjunctive dexamethasone treatment 6
• In lung cancer patients with brain metastases, the impact of steroids on immune checkpoint inhibitor efficacy depends on the patient's NLR 4
• Blood samples for WBC and differential counts should be obtained before the morning steroid dose in transplant recipients to avoid misinterpretation due to steroid-induced changes 3

Monitoring Recommendations

• For patients on chronic steroid therapy, blood counts should be monitored regularly 7
• In patients with hematological disorders, monitoring frequency should be adjusted based on risk level:
  • High-risk patients: Every 3-4 months
  • Moderate-risk patients: Every 3-6 months initially
  • Lower-risk patients: At least annually 7
• For transplant recipients, WBC and differential cell counts should be obtained before the morning steroid dose 3

Pitfalls and Caveats

• Changes in WBC counts due to steroids are unpredictable between individuals but reproducible within the same patient 3
• There is no correlation between steroid dose and magnitude of WBC response 3
• Steroid-induced changes in differential counts can mask or mimic other conditions, leading to diagnostic confusion
• The persistence of reduced eosinophil counts for weeks after steroid discontinuation may affect the interpretation of eosinophil counts as biomarkers in asthma and other conditions 1