Yes, the rising WBC count from 9,000 to 11,000 is most likely related to prednisone therapy and does not indicate infection in this clinical context.
Steroid-Induced Leukocytosis: Expected Response
The modest WBC increase of 2,000 cells/mm³ after 2 days of prednisone 40 mg daily falls well within the expected range of steroid-induced leukocytosis and should not prompt concern for infection in an afebrile patient without infectious symptoms. 1, 2
Magnitude of Expected WBC Rise with Steroids
- Prednisone 40 mg daily is considered a medium-to-high dose, and WBC response typically peaks at 48 hours after steroid administration 2
- Medium-dose steroids produce a mean WBC increase of 1.7 × 10⁹/L (1,700 cells/mm³), while high-dose steroids can increase WBC by up to 4.84 × 10⁹/L (4,840 cells/mm³) within 48 hours 2
- Your patient's increase of 2,000 cells/mm³ is entirely consistent with the expected steroid effect at this dose and timeframe 2
Distinguishing Steroid Effect from Infection
The absence of fever and infectious symptoms strongly argues against infection as the cause of leukocytosis. 3, 4
Key differentiating features:
- WBC count of 11,000 cells/mm³ is below the threshold (≥14,000 cells/mm³) that carries significant likelihood for bacterial infection (likelihood ratio 3.7) 3, 4
- The Infectious Diseases Society of America states that in the absence of fever, leukocytosis, left shift, or specific clinical manifestations of focal infection, additional diagnostic tests may not be indicated 3, 4
- Steroid-induced leukocytosis typically shows a neutrophilia without significant left shift (band forms <16% or absolute band count <1,500 cells/mm³), whereas bacterial infection commonly produces left shift 5, 4
Clinical Recommendation
No further infectious workup is warranted at this time. 3
- Continue monitoring clinical status for development of fever, purulent sputum, or other infectious symptoms 6
- If WBC continues to rise beyond 14,000 cells/mm³ or if infectious symptoms develop, then obtain CBC with manual differential to assess for left shift 3, 5
- Any WBC increase exceeding 4,840 cells/mm³ from baseline, or increases after low-dose steroids, should prompt evaluation for alternative causes including infection 2
Important Caveats
- Corticosteroids are standard therapy for COPD exacerbations (prednisolone 30-40 mg daily for 5-14 days), and systemic corticosteroids improve lung function, oxygenation, and shorten recovery time 6, 7, 8
- The most common causes of COPD exacerbations are respiratory viral infections, though bacterial infections and environmental factors may also trigger events 6
- If the patient develops increased sputum purulence, increased sputum volume, or worsening dyspnea beyond the initial presentation, reassess for bacterial superinfection 6
- Eosinophil count can serve as a marker of steroid compliance and efficacy—undetectable eosinophils suggest adequate steroid effect 1