369 Comparison of Skin and Conjunctival Reactivity to Aeroallergens

BACKGROUND: Diagnosis of allergic conjunctivitis (AC) is based on symptoms and positive skin prick test (SPT) to common aeroallergens. Allergens identified by SPT may not be clinically relevant to the eye. This study aims to compare the skin and conjunctival allergic responses to dust mites and grass pollen. METHODS: 56 subjects (29 ± 11.4 years) with ocular allergy and sensitized to dust mites and/or grass pollens were recruited for the study. Standardized extracts of Dermatophagoides pteronyssinus (Der p 1 83.8 mcg/mL), Blomia tropicalis (Blo t 5 462.5 ng/mL) and Lolium perenne (Phl p 5 399.2 mcg /mL) were used for skin test end point titration. Increasing 2-fold allergen dilutions were tested in forearms until no skin reaction was elicited. The end point was considered the dilution immediately above that one. Conjunctival provocation test (CPT) was performed with progressive doses of allergen (1:32, 1:16, 1:8, 1:4, 1:2) to the involved allergen. All tests were performed after obtaining written informed consent and out of grass pollen season. Subjects should be assymptomatic and off antiallergic medication. RESULTS: Of 82 conjunctival tests (30 Lp; 26 Bt; 26 Dp), 76% (62/82) occurred with 1:8 to 1:2 dilutions, 18% (15/82) with 1:32 to 1:16 dilutions and 6% (5/82) were negative. CPT were positive in 76% of subjects with Der p 1 (10.5–41.9 mcg/mL), Blo t 5 (57.8–231.3 ng/mL) and Phl p 5 (49.9–199.6 mcg/mL). SPT were positive for allergens with 1:1024 to 1:128 dilutions in 22% (18/82), with 1:64 to 1:16 dilutions in 63% (52/82) and with 1:8 to 1:2 dilutions in 11% (9/82). Three subjects had negative SPT. Allergen threshold dose to trigger a response in the skin was lower than in the eye for all 3 allergens tested (P < 0.0001). CONCLUSIONS: Reactivity to aeroallergens in provocation tests requires higher allergen dose for CPT than SPT. Positive SPT with standardized allergenic extracts is predictive of clinical relevance in the diagnosis of allergic conjunctivitis.