The Evolution of Skin Testing in Otolaryngic Allergy

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The Evolution of Skin Testing in Otolaryngic Allergy

Richard L. Mabry

Until the 1930s, it was virtually unheard of for otolaryngologists to test and treat patients for allergy, and those who did do testing utilized the same types of tests employed by general allergists: scratch tests, prick tests, or single dilution intradermal tests. Early efforts at skin testing begin with Blackley,1 who described a primitive form of scratch test in 1873. Intradermal skin tests were performed by Cooke² in 1915. Prick testing dates to the work of Lewis and Grant³ in 1926. Scratch tests have since been abandoned as inaccurate and unsafe,⁴ but prick testing and intradermal skin testing remain in use to the present time.

Almost from the inception of skin testing, some clinicians sought to increase the safety and accuracy of the tests by adding a degree of quantitation to them. In 1911 Leonard Noon⁵ attempted to roughly quantitate the responses to both scratch testing and conjunctival challenge tests. Intradermal and prick testing were semiquantitatively scored by grading systems based on the size of the wheal and flare they produced.

In 1963 Rinkel,⁶ influenced by the earlier work of Hansel,⁷ introduced a concept that was to become the hallmark of skin testing by otolaryngic allergists for decades to come. Using fivefold dilutions of antigens, and starting with an anticipated nonreacting concentration, Rinkel raised intradermal wheals with progressively higher antigen strengths until he found the concentration that first caused a positive wheal. He called this concentration the “endpoint of titration,” and postulated that it represented the strongest concentration of antigen at which immunotherapy could be safely begun. He proved the efficacy of this method in his own clinical experience, and with few modifications, this concept of skin endpoint titration (SET) has remained the benchmark methodology of allergy testing by otolaryngologists since Rinkel introduced it.

Allergists, on the other hand, have traditionally utilized prick testing as their major skin test methodology. Since prick testing introduces much less antigen than single dilution intradermal testing, it is the safer of those two methodologies. However, the argument can be made that if prick testing alone is used, patients with low degrees of sensitivity will be missed.8 Although some allergists perform single dilution intradermal testing to follow up negative prick tests, many do not. It is this philosophical difference that separates the general allergist from the otolaryngic allergist.

Because of confusion about some of the low-dose immunotherapy espoused by Hansel and immunotherapy beginning at the endpoint concentration as recommended by Rinkel, the term skin endpoint titration came to have a pejorative connotation.⁹ In January 2003 the board of directors of the American Academy of Otolaryngic Allergy endorsed the terminology change introduced with the 2003 American Medical Association (AMA) manual Current Procedural Terminology 2003,¹⁰ wherein the broad practice of sequential intradermal testing is known as intradermal dilutional testing (IDT). The term IDT encompasses not only the basic methodology of SET, but also the more recent refinements designed to make testing more efficient and cost-effective.

Under pressure by third-party payers who required that screening prick testing must precede intradermal testing (i.e., the methodology employed by most general allergists), many otolaryngic allergists began to employ a blend of prick testing and intradermal dilutional testing. These methods will be discussed in detail in this book, and have also been described elsewhere.¹¹

No matter whether the otolaryngic allergist chooses to depend entirely on IDT (in either its most complete form or an optimized version) or combine it with prick testing, it is important that the clinician performing allergy testing have a full understanding of all the methods available, their limitations and advantages, and the potential dangers involved in administering allergy skin tests and/or injections. With appropriate training and attention to detail, it is possible to safely and effectively treat the vast majority of allergic patients who present to the otolaryngologist.