Latex Allergy

Erin M. Warshaw, MD

Disclosures
In This Article

Diagnosis

The Figure outlines a reasonable approach to diagnosing latex allergy in a clinical setting. As with any diagnosis, a detailed history and thorough clinical exam is essential. Evidence of risk factors (atopy, occupation, pre-existing hand dermatitis) and history of symptoms (timing, magnitude, situation) should prompt an evaluation. Importantly, delayed-type hypersensitivity to rubber additives and immediate reactions to latex proteins may coexist; therefore, both patch testing and evaluation for latex antibodies may be necessary. A clinical exam showing patchy or diffuse eczema and/or urticaria on the exposed body part is a classic presentation. Hands can transfer allergens to other body parts, especially the face, resulting in unusual presentations. Because allergy to latex is an immediate reaction, it is common for the patient to present for evaluation after symptoms have subsided.

Diagnostic algorithm for clinical diagnosis of latex allergy *Risk of anaphylaxis; +=if positive; –=if negativeModified from Curr Pract Med. 1999:2:142–145.

There are three major categories of tests for confirming a diagnosis of latex allergy: skin tests, in vitro serologic tests, and provocative tests. Most experts feel that a skin prick test with a diluted latex antigen extract is the most sensitive and, therefore, the gold standard for detecting latex allergy. Unfortunately, while commercial skin prick test extracts are available in Europe (Stallergenes, Antony, France) and Canada (Bencard, Toronto, Canada), none are available in the United States. As a result, clinicians sometimes use nonstandardized, office-made extracts produced from mixing glove squares with saline. The stock solution is diluted in saline to 1:1,000,000. Testing is performed by placing a drop of diluted antigen solution on the skin and gently pricking the skin with a lancet. The remaining solution is gently wiped away with blotting paper. Fifteen minutes after application, the wheal is measured by adding the two largest perpendicular axes and dividing the sum by two. A positive reaction is defined as a number equal to or greater than half the value of a histamine control. If no reaction is noted at 15 minutes, then increasing concentrations are subsequently tested. While anaphylactic risk during prick testing is minimized by initially using very diluted solutions, physicians should be prepared with latex-safe resuscitation equipment and epinephrine.

Serologic RAST (radioallergosorbent) tests are in vitro tests in which solid-phase allergen is incubated with serum to induce specific antigen-antibody reactions. Radiolabeled anti-IgE antibodies are mixed with solid-phase allergen-antibody complexes, and bound radioactivity is measured. RAST-like tests available in the United States include: AlaSTAT (Diagnostic Products Corporation, Los Angeles, CA); CAP (Pharmacia, Peapack, NJ); and HYTECH (Hycor Biomedical, Inc., Garden Grove, CA). Sensitivities and specificities range from 74%–97% and 33%–97% respectively.[34] Therefore a negative RAST does not exclude latex sensitivity. Because these tests only measure serologic antibodies, which may decrease after allergen avoidance, they do not provide quantification of latex antibodies bound on tissue mast cells.

Provocative tests include use tests and inhalation challenge tests. A use test involves applying a latex glove directly to a wet hand; a vinyl glove serves as a control. First, one wet finger is exposed to a glove finger for 15 minutes. A positive test is defined as 2–5 urticarial wheals. If no reaction is observed, the entire glove is applied to a wet hand for an additional 15 minutes. If no wheals are noted, exposure can be lengthened to several days or the test can be modified so that the skin is pricked before application of gloves. Inhalation challenge tests involve measuring spirometry at 15–30 minute intervals while subjects handle latex gloves. If no reaction is detected, patients are then asked to blow up latex gloves, expelling the contents slowly into their faces; vinyl gloves are used as controls. These tests are unregulated and carry a risk of anaphylaxis.

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