Should I perform a stool examination (stool exam) and peripheral smear in a 27-year-old patient with eosinophilia (elevated eosinophil count) and a total leukocyte count (TLC) of 9100 cells per microliter?

Evaluation of Eosinophilia in a 27-Year-Old Patient

For a 27-year-old patient with 15% eosinophils and TLC of 9100, stool examination and peripheral blood smear should be performed as part of the initial diagnostic workup to rule out parasitic infections and evaluate for potential hypereosinophilic syndrome.

Initial Assessment of Eosinophilia

The patient presents with significant eosinophilia (15% with TLC of 9100, which calculates to approximately 1365 eosinophils/μL). This level of eosinophilia requires a systematic evaluation:

Step 1: Confirm the Eosinophilia

• Peripheral blood smear examination is essential to:
  • Confirm the eosinophil count
  • Assess eosinophil morphology
  • Rule out other hematologic abnormalities 1
  • Evaluate for potential clonal disorders 2

Step 2: Evaluate for Common Causes of Eosinophilia

1. Parasitic infections:

   • Stool examination is crucial as parasitic infections are the second most common cause of hypereosinophilia 3
   • Multiple stool samples may be needed for adequate sensitivity
   • Specific parasites to consider: strongyloidiasis, toxocariasis, schistosomiasis, filariasis, hookworm 3

2. Allergic disorders:

   • Allergic conditions account for approximately 80% of cases with eosinophilia 3
   • Consider history of atopic diseases (asthma, allergic rhinitis, eczema)

Diagnostic Algorithm

When Eosinophil Count is >1500/μL (Hypereosinophilia)

If the calculated absolute eosinophil count exceeds 1500/μL:

• Comprehensive evaluation for hypereosinophilic syndrome (HES) is warranted
• Additional testing should include:
  • Serum tryptase
  • Vitamin B12 levels
  • Comprehensive metabolic panel with liver function tests 3
  • Consider bone marrow examination 2

When Eosinophil Count is 500-1500/μL

For the current patient (calculated ~1365 eosinophils/μL):

1. Rule out secondary causes:

   • Stool examination for parasites (multiple samples)
   • Peripheral blood smear
   • Medication history (drug reactions)
   • Travel history to tropical/subtropical areas 3

2. Consider gastrointestinal eosinophilic disorders:

   • Eosinophilic esophagitis (EoE) requires endoscopic evaluation with biopsies
   • Eosinophilic gastroenteritis may present with abdominal pain, nausea, and diarrhea 4

Important Considerations

Potential Pitfalls

1. Missing parasitic infections:

   • A single negative stool sample does not rule out parasitic infection
   • Multiple samples and specialized techniques may be needed 3

2. Overlooking eosinophilic gastrointestinal disorders:

   • Eosinophilic gastroenteritis can present with chronic abdominal pain and peripheral eosinophilia 4
   • Requires endoscopic biopsies showing ≥20 eosinophils/HPF in gastric mucosa 4

3. Failure to recognize hypereosinophilic syndrome:

   • HES is defined as persistent eosinophilia >1.5 × 10^9/L with evidence of end-organ damage 2
   • Requires exclusion of secondary causes

Clinical Pearls

• Peripheral blood eosinophil count may provide supportive evidence for eosinophilic disorders but is not diagnostic alone 1
• The degree of elevation of serum eosinophils may correlate with the severity of eosinophilic disorders 1
• Seasonal variations in eosinophil counts may suggest allergic etiology 1

Conclusion

For this 27-year-old patient with 15% eosinophils and TLC of 9100, both stool examination and peripheral blood smear are essential initial diagnostic steps. These tests will help determine whether the eosinophilia is due to a parasitic infection or potentially represents a primary eosinophilic disorder requiring further specialized evaluation.