What is the next test for a patient with suspected allergic rhinitis?

Diagnostic Testing for Suspected Allergic Rhinitis

For patients with suspected allergic rhinitis, skin prick testing is the next recommended diagnostic test due to its high sensitivity, specificity, and clinical utility in confirming the diagnosis. 1

Primary Diagnostic Approach

Skin Testing

• Skin prick testing (SPT) is the preferred initial test for suspected allergic rhinitis 1
  • Provides immediate results (within 15-20 minutes)
  • High sensitivity and specificity for detecting allergen-specific IgE
  • Should use standardized allergen extracts when available
  • Results should include measurements of wheal and erythema for allergens and controls

Blood Testing

• Allergen-specific serum IgE testing is an alternative when:
  • Skin testing is contraindicated (extensive dermatitis, dermographism)
  • Patient is taking medications that suppress skin test responses (antihistamines, tricyclic antidepressants)
  • Patient has a history of severe allergic reactions 1

Testing Algorithm

1. Initial evaluation: Based on history and physical examination findings (rhinorrhea, nasal congestion, sneezing, itchy nose)
2. First-line test: Skin prick testing with relevant allergens
3. Alternative test: Serum-specific IgE testing if skin testing is contraindicated
4. Additional testing: Only if diagnosis remains unclear after initial testing

Evidence Quality and Considerations

• Skin prick testing shows higher correlation with clinical symptoms than nasal smear eosinophilia (71% correlation between nasal eosinophilia and skin prick tests) 1, 2
• Recent evidence indicates nasal smear eosinophilia and blood absolute eosinophil count are only significant in patients with moderate-severe symptoms, not in those with mild intermittent symptoms 3
• The 2015 Clinical Practice Guideline for Allergic Rhinitis specifically discourages routine use of diagnostic imaging 1

Special Situations

• For patients with history-positive but skin test-negative results, nasal smear for eosinophils may be considered as a supplementary test 1
• A positive nasal smear (>10% eosinophils) with negative allergen challenge may indicate non-allergic rhinitis with eosinophilia syndrome (NARES) 1

Common Pitfalls to Avoid

• Don't rely solely on nasal smears for initial diagnosis of allergic rhinitis - they have limited clinical utility with only 71% correlation with skin tests 4, 2
• Avoid routine imaging studies as there are no radiological findings specifically diagnostic for allergic rhinitis 1
• Don't forget to document medications that may suppress skin test responses (antihistamines, some antidepressants) 1
• Don't assume all rhinitis with eosinophilia is allergic - approximately 5.9% of patients may have non-allergic rhinitis with eosinophilia 2

By following this evidence-based approach, clinicians can efficiently diagnose allergic rhinitis and initiate appropriate treatment to improve patient morbidity, mortality, and quality of life.