Does prednisone increase White Blood Cell (WBC) count?

Prednisone Increases White Blood Cell Count

Yes, prednisone does increase white blood cell count (WBC), with increases typically peaking at 48 hours after administration and varying based on dosage. 1, 2

Mechanism and Pattern of WBC Increase

Prednisone causes leukocytosis through several mechanisms:

• Decreased expression of neutrophil adhesion molecules (Mac-1 and L-selectin), reducing neutrophil adhesion to endothelial surfaces 3
• Demargination of neutrophils from blood vessel walls into circulation
• Delayed apoptosis of neutrophils
• Increased release of neutrophils from bone marrow

The pattern of WBC increase typically shows:

• WBC increases can begin as early as the first day of treatment 1
• Peak effect occurs around 48 hours after administration 2
• Higher doses produce larger increases in WBC count 2
• The effect can persist for the duration of therapy, though WBC counts may decrease somewhat after reaching maximal values (typically within two weeks) 1

Magnitude of WBC Increase

The degree of leukocytosis is dose-dependent:

• Low-dose prednisone: Mean increase of 0.3 × 10⁹/L WBCs
• Medium-dose prednisone: Mean increase of 1.7 × 10⁹/L WBCs
• High-dose prednisone: Mean increase of 4.84 × 10⁹/L WBCs 2

In some cases, WBC counts may exceed 20,000/mm³ 1

Differential Cell Count Changes

The leukocytosis from prednisone primarily affects specific white blood cell types:

• Increased: Neutrophils (polymorphonuclear cells) - primary contributor to the elevated WBC
• Increased: Monocytes
• Decreased: Eosinophils
• Decreased: Lymphocytes (variable degree of lymphopenia) 1

Clinical Implications

This effect has important clinical implications:

1. Diagnostic confusion: Prednisone-induced leukocytosis can be mistaken for infection, especially in immunocompromised patients

2. Differentiating from infection:

   • Prednisone-induced leukocytosis rarely shows a left shift (>6% band forms)
   • Toxic granulation is uncommon in steroid-induced leukocytosis but common in infection 1
   • Increases larger than 4.84 × 10⁹/L after high-dose steroids suggest other causes of leukocytosis 2

3. Timing of blood draws: For patients on prednisone, WBC counts should ideally be obtained before the morning steroid dose to avoid misinterpretation 4

Variability Between Patients

The WBC response to prednisone shows significant inter-individual variability:

• A given patient's response to a specific dose is generally reproducible
• However, different patients may show different magnitudes of response to the same dose 4
• The response is not consistently correlated with prednisone dose across all patients 4

Understanding this effect is crucial when monitoring patients on prednisone therapy, particularly when evaluating for possible infection or when making clinical decisions based on WBC counts.