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

Abstract

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 ( Phleum pratense), despite little literature to support the claim that Phleum 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 ( Festuca pratensis) 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 CPT code 95004 ( Current Procedural Terminology). 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 Phleum and Festuca. In total, 1239 patients had a positive result for Phleum or Festuca. Of these, 479 (38.6%) tested positive for Festuca alone, while 342 (27.6%) and 418 (33.7%) tested positive for Phleum alone and Phleum+ Festuca, respectively. Conclusion Clinical cross-reactivity among Pooideae members may not be as complete as traditionally thought. P pratense may not be the most antigenically representative subfamily member, and other grasses may need to be included in skin prick testing.