Should I repeat Complete Blood Count (CBC) to confirm eosinophilia before proceeding with additional testing?

Repeating CBC to Confirm Eosinophilia Before Additional Testing

Yes, you should repeat a CBC to confirm eosinophilia before proceeding with additional testing. 1 This approach ensures diagnostic accuracy and avoids unnecessary invasive procedures.

Rationale for Confirming Eosinophilia

Eosinophilia (defined as >450-550 cells/μL) can be caused by numerous conditions, and confirmation is essential for several reasons:

• Fluctuating levels: Eosinophil counts can naturally fluctuate
• Medication effects: Certain medications may temporarily affect eosinophil counts
• Diagnostic accuracy: Confirmation reduces the risk of false positives
• Resource optimization: Prevents unnecessary specialized testing

Diagnostic Algorithm

1. Initial finding of eosinophilia

   • Document exact eosinophil count
   • Review current medications (especially recent changes)
   • Assess for symptoms of common causes (allergic, parasitic, etc.)

2. Repeat CBC after 1-2 weeks

   • If eosinophilia persists → proceed with further evaluation
   • If normalized → consider transient cause or lab error

3. For persistent eosinophilia:

   • Withdraw proton pump inhibitors (PPIs) for at least 3 weeks before any endoscopic procedures 1
   • Document PPI withdrawal on lab requisitions and endoscopy requests
   • Proceed with targeted testing based on clinical presentation

Special Considerations

Eosinophilic Esophagitis (EoE) Evaluation

The British Society of Gastroenterology strongly recommends that PPIs should be withdrawn for at least 3 weeks prior to endoscopy and biopsy when evaluating for EoE 1. This is crucial as PPIs can suppress esophageal eosinophilia below diagnostic levels (15 eosinophils per 0.3 mm²), potentially obscuring the diagnosis.

High Clinical Suspicion Cases

In cases with high clinical suspicion but initial negative findings, repeat testing is warranted:

• If initial histology was not diagnostic but symptoms or endoscopic features suggest EoE, repeat endoscopy with adequate biopsies should be considered 1
• A retrospective case series found that 36% of patients with persistent symptoms had diagnostic histology on repeat biopsies 1

Early Diagnosis Benefits

Early diagnosis and treatment of conditions associated with eosinophilia may prevent long-term complications:

• In EoE, diagnostic delays correlate with increased stricture rates (17% with <2 year delay vs 71% with >20 year delay) 1
• Early intervention may prevent fibrosis and permanent tissue remodeling 1

Pitfalls to Avoid

1. Premature specialized testing: Avoid expensive or invasive testing before confirming persistent eosinophilia
2. Ignoring medication effects: Particularly PPIs which can mask eosinophilic conditions
3. Incomplete withdrawal periods: Ensure adequate time off medications that affect eosinophil counts
4. Inadequate sampling: When proceeding to tissue sampling, ensure adequate specimens (e.g., at least six biopsies from different anatomical sites for EoE) 1

By confirming eosinophilia with a repeat CBC before proceeding with specialized testing, you can ensure accurate diagnosis while minimizing unnecessary procedures and optimizing patient care.