Allergen Skin Testing for AsthmaticsPricks and Wheals

Paul Enright, Tucson Arizona

Catherine Foss, Durham NC

AARC. December 10, 2003

Who, when, where, & why, and how

Who should administer skin tests?

Usually performed by nurses who work for an allergist But few asthmatics are ever referred to an allergist A certification or credential is not needed

but training and experience are worthwhile

RTs and PF techs should provide this lung test

When should skin tests be done?

For all patients with persistent asthma All ages: infants to the elderly 90% of children with asthma are atopic. Half of adults with asthma are atopic.

Atopic = Atopy = Allergic (IgE) =sensitized to one or more allergens

Where should skin tests be done?

Currently, the majority are done in an allergist’s office. However, they can be safely done in any medical setting. Skin prick tests for aeroallergens have no risk of anaphylaxis.

Why perform allergen skin tests?

To reduce the need for asthma drugs– Drugs are expensive and have side-effects

To guide environmental mitigation efforts to reduce indoor allergen levels

Environmental interventions have been proven to improve asthma control.

Allergy shots are less frequently needed

Traditionally, skin tests were used to guide immunotherapy for asthma and rhino-sinusitis, but then along came …

Nonsedating antihistamines (10 cents each)

Corticosteroid nasal sprays (Flonase)

Inhaled corticosteroids (Flovent)

Leukotriene inhibitors (Singulair)

Combination inhalers (Advair & Symbicort)

Anti-IgE shots (Xolair $$$)

Pathophysiology of skin tests

1. T lymphocytes activated by IgE

2. Mast cells degranulate, spilling cytokines

3. Vasodilation causes edema in 5 min

4. Neutrophil influx in 10 min

5. Late phase reaction in 4-12 hoursLymphycyte and eosinophil inflammation

Wheal (itchy raised bump) and Flare (red erythema)Just like the inflammation of asthmatic airways

Tests for allergic sensitization

Skin tests– Prick/puncture (SPT)

– Scratch (historical interest only)

– Patch (for contact dermatitis only)

– Intradermal (sensitive but risky)

Specific IgE levels in the blood– RAST– ImmunoCAP

Specific challenge tests– Eye, nose, or lungs

Asthmatic kids are allergic to their home

Roaches 70% (45% Seattle – 80% Bronx) Mites 60% (40% Chicago – 85% Dallas)

Molds 50% (40% NYC – 75% Dallas)

Cats 45% (30% Chicago – 60% NYC)

Rodents 35% (15% Tucson – 50% Boston)

Dogs 20%

95% of children with asthma are atopic.Half are sensitized to 3 or more indoor allergens.

1059 ICAS children, Environ Health 2002

Asthmatic homes have many allergens

Cockroaches 60% Smoking parent 50% Dampness/mold 45% Rodents 40% Cat or dog 30%

These parental reports under-estimated the measured allergen levels.Allergen rates in the homes of asthmatic adults are generally lower.

1000 homes, ICAS, Environ Health 20021000 homes, Europe, Clin Exp Allergy 2002

How to perform a skin prick test

1. Load antigens, +, - controls into the tray2. Explain the test3. Ask about asthma control4. Ask about medications

No antihistamines for 3 days before (false negative results)

Tricyclic antidepressants also block the histamine responseBeta-blockers make treatment of systemic SEs difficult

5. Clean the inside of the left arm with alcohol wipes6. Mark antigen targets about an inch apart

Step by step … continued

7. Ensure there is liquid (antigen) on the tines

8. Apply each antigen (prick) carefully

9. Blot excess fluid from the arm

10. After 15 min, measure wheal diameters

11. Control the itching (alcohol wipe and steroid cream)

12. Explain the results and discuss pos antigens

Try ballpoint pen tracing and translucent tape

Alternative antigen application methods

Prick 45 deg to skin, then lift skin Puncture 90 deg to skin, moderate pressure Scarify90 deg to skin, then rotate half turn

Larger reactions will occur with scarification

Antigens may be placed on the upper back– but larger reactions occur (more sensitive skin)

Stick with the same method.

Allergen preparations

Choose indoor allergens assoc with asthma– House dust mites (der p and der f)

– Mold mix, Cockroach, Cat, Dog, Mouse

Mixtures give better sensitivity but less specificity and reproducibility

Units of measure– AU/mL (Allergy Units, U.S. FDA)

– BU/mL (Nordic Biological Units, Europe)

– ug/mL or mg/L for single (recombinant) antigens

Safety

Use disposable lancets (tines) Don’t cause bleeding (wear gloves?) Don’t let the patient leave for 30 min Have albuterol and an Epi-Pen available

Application devices for skin testing

Plastic tines (1-2mm long)

– Multi-test II (Lincoln)

– Derma Pick (Greer)

– AllerSharp (Bayer)

– Phazet (Pharmacia)

Stainless steel lancets– QuinTest (Hollister-Stier)

– Morrow-Brown (AllerSharp)

– 27 gauge hypodermic needles (not)

Plastic allergen applicators

Duotip

Allersharp

Greer Pick

Quintest

A positive prick defined

Mean wheal diameter at least 3mm Be less confident of small responses (2-3mm) When dermatographism occurs, the negative control

(50% glycerin) wheal is >2mm (so subtract its size) Ensure that the positive control wheal (histamine) is

about 5mm in diameter

Food allergies?

True food allergies are very rare after age 2 Skin tests for food allergies are unreliable Blind testing with food capsules Specific IgE tests for foods being developed

Home allergen mitigation methods

Mattress and pillow covers (mites) Remove bedroom carpeting Integrated pest management (roaches) Fix leaks, reduce humidity (mold) Swimming lessons (cats) HEPA air purifier (smoke, mold, pet)

Efforts to reduce home allergens work

469 children with moderate asthma were randomized to environmental intervention, which was based on allergen skin testing.

Mom was called every 2 months. At 2–12 months, the intervention group had

significantly fewer days of cough and wheeze, fewer missed school days, and fewer E.R. visits.

Reductions in bedroom allergen levels were associated with reduced asthma morbidity.

ICAS, March 2002 AAAAI presentation

Conclusions

Everyone with asthma should get skin testing,with the goal of reducing their need for asthma drugs.

Reducing allergen exposures improves asthma control. RTs can easily and safely perform skin tests,

another respiratory service for community physicians.

References

Crain EF, et al. Home and allergic characteristics of children with asthma in seven U.S. urban communities and design of an environmental intervention: the Inner City Asthma Study. Environ Health Perspect 2002; 110:939-945.

de Blay F, et al. Medical indoor environment counselor (MIEC): role in compliance with advice on mite allergen avoidance and on mite allergen exposure. Allergy 2003; 58:27-33.

Weiss ST, et al. The prevalence of environmental exposure to perceived asthma triggers in children with mild to moderate asthma: data from the childhood asthma management program (CAMP). J Allergy Clin Immunol 2001; 107:634-640.

Jaen A, et al. Specific sensitization to common allergens and pulmonary function in the European Community Respiratory Health Study. Clin Exp Allergy 2002; 32:1713-1719.

Host A, et al. Allergy testing in children: why, who, when, and how? Allergy 2003; 58:559-569.

References (continued)

Gordon BR. Allergy skin tests for inhalants and foods: comparison of methods in common use. Otolary Clinics No Amer 1998; 31:35-53.

Nelson HS. Variables in allergy skin testing. Allergy Proc 1994; 15:265-268.

Williams PB, et al. Are our impressions of allergy test performances correct? Ann Allergy Asthma Immonol 2003; 91:26-33.

Ricci G, et al. A comparison of different allergometric tests... Allergy 2002; 58:38-45.

Simpson BM, et al. NAC Manchester asthma and allergy study: risk factors for asthma and allergic disorders in adults. Clin Exper Allergy 2001; 31:391-399.

www.greerlabs.com www.hollister-stier.com www.allersharp.com