Short communication Diagnosticvalueofscratch-chambertest,skinpricktest,histamine release and specific IgE in birch-allergic patients with oral allergy syndrome to apple Birch-allergicpatientsoftenreportoralallergysymptoms (OAS)afteringestingcross-reactingfruitsandvegetables. Theoralallergysyndromeconsistsofitchingandswelling of the lips, the oral mucosa and the soft palate after eating fresh fruits or vegetables (1–5). The cross-reactivity is on a molecular level explained by homology between the major allergens from apple (mal d1) and Bet v 1 from birch (6–8). It is well known that skin prick test (SPT) with fresh fruits and vegetables demonstrate a higher diagnostic sensitivity than commercial extracts (9–11). However, usingfreshfruitindailypracticemaybeaproblemasthe allergencontentvariesbetweendifferentapplestrainsand maturation stages (12–14). Previous studies have investigated the value of scratch tests (15–21). Apple tends to dry out quickly when applied to a scratch, but covering the scratch with a Finn chamber (Epitest, Helsinki, Finland) prevents drying out of the apple (22, 23). The SCT is a controversial test, as it is no longer recommended by the American Medical Association CouncilofScientificaffairsbecauseofsignificantnumber of false positive irritative reactions, it is not as reprodu- cible as the SPT and it may be more painful than SPT (24). Documentation is however sparse. Determination of histamine release (HR) and specific immunoglobulin E (IgE) to apple has been examined in several studies (4, 9, 25–28), but no data on a compar- ison between the CAP system (Pharmacia Diagnos- tic, Uppsala, Sweden) and the Magic Lite (ML) test (ALK- ABELLO ´ , Laboratories, Hørsholm, Denmark) in relation to apple are available. The aims of the study were to evaluate the diagnos- tic value of the SPT, the SCT, histamine-release, specific IgE (CAP and ML) in birch-allergic patients with OAS to apple, and to compare different apple extracts in the skin prick, the scratch-chamber and the HR testing. Material and methods Patients Ten patients with clinical allergy to birch pollen, a positive SPT to birch, and a positive case history of OAS to apple. Background: The aim of the study was to examine the diagnostic value of skin pricktest(SPT),scratch-chambertest(SCT),histaminerelease(HR)andspecific immunoglobulin E (IgE) in birch-allergic patients with oral allergy syndrome to apple. Methods: Ten birch-allergic patients with oral allergy syndrome to apple and 10 control subjects were included. All were tested with SPT, SCT, HR and specific IgE [CAP, Pharmacia, Sweden and Magic Lite (ML), ALK-ABELLO ´ , Denmark]. Results: The SPT with apple, acetone extract of apple (A72) and commercial apple extract showed sensitivities of 0.80, 0.90 and 0.10, respectively. The SCT with the same extracts showed sensitivities of 0.30, 0.50 and 0.20, respectively. The sensitivity of specific IgE to apple were 0.90 (CAP) and 0.10 (ML). The sensitivityoftheHRtestwas90%(A72),and25%usingthecommercialextract. Conclusion: TheSPTandHRtestwithappleandA72showedagooddiagnostic value with a sensitivity of more than 70% and a specificity of 100%. The SCT showed a poor sensitivity to apple, A72 and commercial apple extract. The ML test was not suitable in detecting specific IgE to apple compared with the CAP test. In daily practice a detailed case history about symptoms of oral allergy syndrome combined with a SPT with fresh apple peel or A72 will be useful. M. Osterballe 1 , R. Scheller 1 , P. Stahl Skov 2 , K. E. Andersen 1 , C. Bindslev-Jensen 1 1 Allergy Center, Department of Dermatology, Odense University Hospital, Denmark; 2 Reference laboratoriet, Copenhagen, Denmark Key words: apple; CAP; food allergy; histamine release; Magic Lite; oral allergy symptoms (OAS); scratch chamber; skin prick; specific IgE. Morten Osterballe Allergy Center Department of Dermatology Odense University Hospital Sdr Boulevard 29 DK 5000 Odense C Denmark Accepted for publication 18 April 2003 Allergy 2003: 58: 950–953 Printed in UK. All rights reserved Copyright Ó Blackwell Munksgaard 2003 ALLERGY ISSN 0105-4538 950