Allergy Screening

Aka: Allergy Screening, Allergy Test, Skin Testing

1. Preparation
   1. Have Epinephrine and Albuterol available
   2. Discontinue Antihistamines before testing
      1. Second generation Antihistamines: 2 weeks before test
      2. First generation Antihistamines: 3 days prior to test
      3. Other Antihistamine-type agents to stop before test
         1. Phenothiazine
         2. Tricyclic Antidepressants
         3. Anticholinergic Medications
         4. H2 Receptor blocking medications (e.g. Ranitidine)
   3. Inhaled Corticosteroids do not affect test
   4. Short-term Systemic Corticosteroids do not affect test
2. Indications
   1. Refractory Allergic Rhinitis
   2. Refractory Asthma
   3. Food Allergy or drug allergy suspected
   4. Insect sting allergy suspected
3. Contraindications to Skin Testing
   1. Severe Eczematous Dermatitis
   2. Dermatographism
   3. History of Anaphylaxis
   4. Very young
   5. Unable to discontinue Antihistamines
   6. Uncontrolled Asthma (Peak expiratory flow < 75%)
4. Devices
   1. Morrow-Brown Needle
   2. Multi-Test (Lincoln Diagnostics)
   3. Quintest (Bayer)
   4. Modified RadioAllergoSorbent Test (RAST)
   5. Quidel finger stick device
5. Technique
   1. Test 6-10 antigens to determine presence of IgE disease
   2. Use Controls
      1. Positive Control: Histamine
      2. Negative Control: Glycerol-Saline
   3. Read test 15 minutes after application of allergan
      1. Positive if wheal diameter 3 mm > negative control
   4. Use Regional Allergy Screening guidelines
   5. Relies on cross reactivity among antigen groups
      1. Tree
      2. Grass
      3. Weed
      4. Mold
      5. House Dust mite
      6. Cat
6. Interpretation
   1. All Tests negative: No further testing needed
   2. One or more inhalants positive: Complete regional panel
   3. Dust mite only positive: No further testing needed
      1. Avoid Dust mites
      2. Consider Immunotherapy
   4. Cat only positive: No further testing needed
      1. Avoid exposure and reduce dander
      2. Consider Immunotherapy
   5. If Positive Control is Negative
      1. Try RAST testing
      2. Patient may be on Antihistamine or steroid
         1. IF short acting Antihistamine
            1. Stop Antihistamine and retest after 2 days
         2. IF long acting Antihistamine
            1. Stop Antihistamine and retest after 3-4 weeks
   6. If reaction occurs to Negative Control
      1. Dermatographism
   7. Intradermal Allergy Test Indications
      1. Suspected Insect Sting Allergy (e.g. bee, hornet)
      2. Suspected Drug Allergy (e.g. Penicillin, anesthetic)
7. References
   1. (1999) NPI Allergy Testing Conference, Las Vegas
   2. James (2002) Am Fam Physician 66(4):621-6