Means of increasing sensitivity of an in vitro diagnostic test for aspirinintolerance

Background Pseudo-allergic reactions caused by aspirin (acetyl salicylic ac id; ASA) often resemble immediate-type hypersensitivity reactions consistin g of urticaria and angioedema or rhinoconjunctivitis, asthma and nasal poly ps. In the last few years, a new in vitro, assay based on determination of sulfidoleucotrienes from isolated leucocytes (cellular allergen stimulation test - CAST) has been introduced for type I allergies and pseudoallergic r eactions. In ASA intolerance, there is only limited experience using this a ssay with - in some studies - only moderate sensitivity. Furthermore, the n ecessity to use freshly isolated leucocytes from untreated patients is inco nvenient for routine settings. Objective The purpose of our study was to search for possibilities of incre asing the sensitivity of the test and to use stored blood samples which wou ld permit shipping, two requirements for the clinical suitability of this t est. Patients and methods Leucotriene release in response to ASA and other non-s teroidal anti-inflammatory drugs (NSAIDs) was analysed in 38 ASA-intolerant patients (predominantly airway-related symptoms n = 72; predominantly cuta neous symptoms n = 16) and 50 controls. The diagnosis of ASA intolerance wa s established by history and placebo-controlled oral challenge tests. Results Using 24h-stored leucocytes obtained from 10 ASA-intolerant patient s and 10 healthy controls there were no significant differences of leucotri ene release by resting, ionomycin-, and anti Fc epsilon RI alpha-stimulated leucocytes compared with freshly isolated leucocytes. Analysis of ASA + C5 a-mediated leucotriene release by stored blood samples in combination with indomethacin- and diclofenac-mediated leucotriene release in ASA-intolerant patients (n = 38) resulted in an increased sensitivity (from 50 to 72.7% i n ASA-intolerant patients with predominantly airway-related symptoms and fr om 81 to 100% in ASA-intolerant patients with predominantly skin symptoms) compared with assays in which only ASA + C5a-mediated leucotriene release h as been determined. Moreover, the specificity of the assay remained high (9 6.7% when analysing different NSAIDs compared with > 99%, when analysing on ly ASA + C5a-mediated leucotriene release). Conclusion In vitro stimulation with ASA + C5a leucocyte stimulation with o ther NSAIDs should be performed to achieve a higher sensitivity. This findi ng can be explained by the clinical observation of a high ratio of cross-re activities between the mentioned NSAIDs.