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    Contact dermatitis: Patch testing is on the rise due to recent developments

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    Dr. Mowad
    Scottsdale, Ariz. — Patch testing is the gold standard for diagnosing allergic contact dermatitis. The number of dermatologists who patch test is on the rise.

    According to one expert, the increase in patch testing is the result of several recent developments in managing allergic dermatitis patients, thus making patch testing more appealing.

    The introduction of the standardized T.R.U.E. (Thin-Layer Rapid Use Epicutaneous) test simplified the procedure. This is a patch testing system that uses pre-impregnated allergens in each chamber.

    The ready-prepared patch test simply has to be taped to the back of the patient, significantly reducing the time of preparation.

    Time saving

    "In our clinic, we patch test each patient to at least 60 chemicals, and each of these chemicals is poured out by hand into their respective chambers.

    "It is, therefore, understandable that in a busy practice, physicians may not want to perform expanded patch testing because it is more time-consuming.

    "The T.R.U.E. test helps save a lot of time here and makes patch testing more practical and appealing for the physician suspicious of allergic contact dermatitis," says Christen M. Mowad, M.D., associate professor, department of dermatology, Geisinger Medical Center, Danville, Pa.

    Limitations

    One of the big limitations of the T.R.U.E. test, however, is that it initially only tested for 24 chemicals. Most patch testing centers regularly test for 60 or more allergens in one visit.

    According to Dr. Mowad, the drawback with smaller testing series, such as the T.R.U.E. test, is that they do not completely evaluate the patient's allergens.

    Dr. Mowad says many studies show patients are not being completely evaluated when smaller test series are employed.

    Recently, the T.R.U.E. test added five additional allergens to its tray — diazolidinyl urea, imidazolidinyl urea, budesonide, tixocortol-21-pivalate and quinolone mix.

    According to Dr. Mowad, these additions will help increase the capture rate of allergens and will prove more useful.

    However, many important allergens will still be missing from the testing system, and patient allergens will still be missed, he says.

    Resources

    Other new patch testing resources include a new allergen supplier, AllergEAZE (Smart Practice, Canada), which offers a new allergen test series and boasts a more simplified system with color-coded identifiers.

    Also, resources for educating patients on allergens have evolved, with an updated CARD (Contact Allergen Replacement Database) system now in use.

    An allergen replacement database is also available that helps identify replacement products for patients who need to avoid certain allergens.

    "What we have done in the past is tell patients what they have to avoid. With the CARD system, allergens that the patient is allergic to are entered into a system, and the database will then tell you all of the things that the patient can use, rather than telling you all of the things that they need to avoid," Dr. Mowad tells Dermatology Times.

    According to Dr. Mowad, this approach is somewhat easier and more user-friendly. The CARD system has been updated so potential allergens that will cross-react with the allergens that the patient tested positive for can also be excluded.

    The database is steadily growing and is updated yearly, and has become a very useful resource for physicians and their patients.

    In order to gain access to the database, one must be a member of the American Contact Dermatitis Society. Dr. Mowad routinely uses the database, and finds it very helpful in managing her patients and quickly letting them know what they can use once their allergens are identified.

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