Diagnostic value of scratch-chamber test, skin prick test, histamine release and specific IgE in birch-allergic patients with oral allergy syndrome to apple

Background: The aim of the study was to examine the diagnostic value of skin prick test (SPT), scratch-chamber test (SCT), histamine release (HR) and specific 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 sensitivity of the HR test was 90% (A72), and 25% using the commercial extract. Conclusion: The SPT and HR test with apple and A72 showed a good diagnostic 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.