Comparison of skin prick tests with specific serum immunoglobulin E in the diagnosis of fungal sensitization in patients with severe asthma.

Background: It has been shown that patients with allergic bronchopulmonary aspergillosis (ABPA) and patients with severe asthma with fungal sensitization (SAFS) can benefit from antifungal therapy. It is not known whether allergy skin prick tests (SPT) or specific IgE tests are more sensitive in the identification of patients who are sensitized to fungi and who are therefore candidates for antifungal therapy.

Objectives: To compare SPT and specific serum IgE tests for fungal sensitization in patients with severe asthma.

Methods: We have undertaken SPT and specific serum IgE tests to six fungi (Aspergillus fumigatus, Candida albicans, Penicillium notatum, Cladosporium herbarum, Alternaria alternata and Botrytis cineria) and specific serum IgE test for Trichophyton in 121 patients with severe asthma (British Thoracic Society/SIGN steps 4 and 5).

Results: Sixty-six percent of patients were sensitized to one or more fungi based on SPT and/or specific serum IgE results. Positivity to SPT and/or specific serum IgE was as follows: A. fumigatus 45%, C. albicans 36%, P. notatum 29%, C. herbarum 24%, A. alternata 22%, B. cineria 18%, Trichophyton 17% (specific serum IgE only). Concordance between the tests was 77% overall but only 14-56% for individual fungi. Twenty-nine (24%) patients were sensitized to a single fungus and seven (6%) were sensitized to all seven fungal species. Fifty percent of patients were sensitized to fungal and non-fungal extracts, 21% were sensitized only to non-fungal extracts, 16% were sensitized only to fungal extracts and 13% had no positive tests.

Conclusion: This study is consistent with previous reports that fungal sensitization is common in patients with severe asthma. At present, it remains necessary to undertake both SPT and specific serum IgE testing to identify all cases of fungal sensitization. This may be important in the identification of patients with ABPA and SAFS who may benefit from antifungal therapy.