Abstract

COUTO, Mariana et al. The use of local anesthetics does not affect intradermal tests results. Rev Port Imunoalergologia [online]. 2013, vol.21, n.4, pp.259-266. ISSN 0871-9721.

Introduction: Intradermal tests (IDT), although painful, are essential for the diagnosis of drug and hymenoptera venom allergy. The use of topical anesthetics significantly reduces the pain associated with skin tests. Objective: To determine the effects of an anesthetic patch with prilocaine and lidocaine (EMLA®) on the results of IDT used for the diagnosis of drug and venom allergy. Methods: Cross -sectional controlled study including patients with suspected drug or venom allergy which underwent IDT during diagnostic workup. Informed written consent was obtained. The topical anesthetic was placed according to the manufacturer’s instructions for 1 hour. The IDT that were positive, as well as positive (histamine 10mg/dL skin prick test) and negative controls, were repeated on the anesthetized area. The same procedure was performed on patients with negative IDT to assess false positives. Results: Forty-four patients (30 female, average age 44±19 years) performed 53 IDTs: 45 with drugs and 8 with hymenoptera venom. The average wheal diameter of histamine without EMLA® was 4.9mm [IC95% 4.5;5.2] and with EMLA® 4.8mm [IC95% 4.4;5.1]. The increase in average wheal diameter of the IDT with drugs was 4.9mm [IC95% 4.0;5.9] without anesthesia and 4.9mm [IC95% 3.8;6.0] with anesthesia. Regarding venoms, the average increase without EMLA® was 3.9mm [IC95% 2.7;5.1] and with EMLA® 4.7mm [IC95% 2.9;6.5]. No differences were found between tests performed with and without EMLA® with respect to histamine (p=0.36), saline controls (p=0.40), and IDT (p=0.72). None of the previously negative IDTs were positive with the use of EMLA® or vice versa. Conclusions: This is the first study to evaluate the use of a local anesthetic on IDT results for diagnostic work -up of drug and venom allergy. Its use did not interfere with test results. The introduction in clinical practice will allow improving patient comfort

Keywords : Drug allergy; intradermal tests; local anesthetic; venom allergy.

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