Q:

What are the practical aspects of performing intradermal drug tests. What volume is injected, when is the test read, and what is considered positive? I'm aware of the irritative concentrations.

A:

Thank you for your recent inquiry.

First, there is an excellent article regarding allergy testing with a nice discussion of intradermal testing published by the World Allergy Organization. The link to this article, which is available to you at no charge online, is copied below:

http://www.worldallergy.org/professional/allergic_diseases_center/allergy_diagnostic/

All intradermal tests are done using the same technique. The same volume that one would apply for testing to allergen is used for testing to drugs and vaccines. One employs the same syringes as well. The tests to aeroallergens, drugs, vaccines, and venoms are all read at the same time (15 to 30 minutes after application). The criteria used to establish a positive test is roughly the same for all allergens, regardless of whether they are vaccines, drugs, venoms, or aeroallergens. One uses the same positive and negative controls.

Therefore, the only difference between intradermal testing to drugs, vaccines, venoms, and allergens is the concentration employed. This varies with the agent tested, and in many instances there is no validated concentration for a specific drug. However, there are references which have dealt with this issue and have established validated, non-irritating concentrations for several drugs and vaccines. An excellent reference, for example, to skin testing with antibiotics is:

Nonirritating intradermal skin test concentrations to commonly prescribed antibiotics. Journal of Allergy and Clinical Immunology 2003, Volume 112, Issue 3, Pages 629-630.

An excellent reference for skin testing using validated concentrations to vaccines is:

Irritant skin test reactions to common vaccines. Journal of Allergy and Clinical Immunology, 2007 (August); 120(2):478-481.

In summary, the technique for intradermal skin testing does not vary according to the allergen tested. The only thing that varies is the concentration. There are not validated skin test concentrations for all drugs, but we do have reasonably well validated concentrations to be used for antibiotics and vaccines. To find whether or not a drug not contained in the references above has a validated, non-irritating concentration that can be employed, one would have to do a search for previously employed skin tests to that agent using Pub Med or a similar site.

Thank you again for your inquiry and we hope this response is helpful to you.

Sincerely,
Phil Lieberman, M.D.

AAAAI - American Academy of Allergy Asthma & Immunology