Comparison between skin prick test and serum immunoglobulin E by CAP system to inhalant allergens.

Background: Skin prick tests (SPTs) and measurements of serum specific immunoglobulin E (sIgE) antibodies are the most commonly used diagnostic tools for confirming sensitization. However, disagreement between the tests has been observed.

Objective: To compare SPT and the CAP system for diagnosis of sensitization to common inhalant allergens.

Methods: Subjects included 2,635 patients 10 to 90 years old who underwent analyses by SPT and CAP at the Dong-A University Hospital (Busan, Korea) from June 2011 through May 2016. The 2 test results were compared for 17 inhalant allergens.

Results: Agreement between the SPT and sIgE level was 75.3%. Overall agreement was moderate (κ = 0.59), with strong agreement for house dust mites and birch (κ > 0.7) and weak agreement for Tyrophagus putrescentiae and dog (κ < 0.3). When CAP was compared with SPT as the reference, the sensitivity was 75.8% and the specificity was 75.2%. Mean wheal size by SPT showed a positive correlation with sIgE levels (r = 0.59), which decreased with age.

Conclusion: There was a discrepancy between SPT and CAP for diagnosing allergic sensitization among inhalant allergens. The allergic sensitization and correlation between the tests decreased with age. Cautious interpretation of the clinical relevance of allergen sensitization based on SPT and CAP results is required, especially in older patients.