T U E S D A Y 802 Predicting Shrimp Allergy Using Skin Prick Test, Specific IgE to Shrimp and Rpen a1 in Area with High Prevalence of House Dust Mite Sensitization Jaichat Mekaroonkamol, MD, Pantipa Chatchatee, MD, Jarungchit Ngamphaiboon, MD, Piyawadee Lertchanaruengrith, MD, Narissara Suratannon, MD; King Chulalongkorn Memorial Hospital, Bangkok, Thailand, Division of Allergy and Immunology, Department of Pediatrics, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand. RATIONALE: In areas with high HDM exposure and high shrimp consumption, diagnosis of shrimp allergy is a clinical challenge since sensitization to both allergens frequently occurs. The aim of this study was to evaluate role of skin prick test(SPT), specific IgE(sIgE) to shrimp and rPena1 in the diagnosis of shrimp allergy in area with high prevalence of HDM sensitization. METHODS: Fifty-one participants with sensitization to both shrimp and Dermatophagoides pteronyssinus(Derp) as demonstrated by SPT were enrolled. Clinical reactions to shrimp were determined. SIgE to Der p, shrimp and rPen a1 were analyzed. RESULTS: Patients were divided into 2 groups; shrimp allergy(n522) and shrimp tolerance(n529). About half (54%) of shrimp allergic patients had anaphylaxis while 30 % had only oral allergy syndrome. Compared to shrimp tolerant subjects, shrimp allergic subjects had significant larger SPT wheal size(7vs4.5 mm,p50.003) and higher sIgE levels to shrimp(2.36vs0.21 kUA/l,p 3.5 mm or positive shrimp sIgE(>0.35 kUA/) provided 90% sensitivity and negative predictive value of 0.86. SIgE to rPen a1 had low sensitivity(45%) but high specificity(85%) and positive predictive value of 0.71 with the cut-off level of 0.35 kUA/L. Size of SPT, levels of shrimp sIgE and sIgE to rPena1 did not differ between anaphylactic and non-anaphylactic patients. CONCLUSIONS: In double sensitized patients with unclear clinical reaction to shrimp, SPT and sIgE to shrimp can be used as screening tests while sIgE to rPen a1 adds diagnostic value for predicting clinical reaction. SIgE to rPen a1 is not a severity marker of shrimp allergy in our population.