Cross-reactivity in Skin Prick Test Results of Members Within Pooideae Subfamily.

Objective: Molecular similarities of grass pollen antigens have led to the view that cross-reactivity exists within members of the Pooideae subfamily of grasses. This has resulted in testing for only the most antigenically representative member of Pooideae, Timothy grass (), despite little literature to support the claim that is the most representative member or that in vitro cross-reactivity correlates with in vivo cross-reactivity. The aim of the study was to determine if patients with allergic rhinitis symptoms and positive skin prick test results to meadow fescue () also have positive results to Timothy grass.

Study Design: Retrospective cross-sectional study.

Setting: Tertiary care center in middle Missouri.

Methods: A retrospective chart review identified patients ≥12 years old with a diagnosis of allergic rhinitis who underwent skin prick testing between March 2016 and July 2018, by using a search with code 95004 (). Positive skin prick test results were based on wheal produced ≥3 mm than the negative control.

Results: After review of 2182 charts, 1587 patients met criteria to test for and . In total, 1239 patients had a positive result for or . Of these, 479 (38.6%) tested positive for alone, while 342 (27.6%) and 418 (33.7%) tested positive for alone and +, respectively.

Conclusion: Clinical cross-reactivity among Pooideae members may not be as complete as traditionally thought. may not be the most antigenically representative subfamily member, and other grasses may need to be included in skin prick testing.