Exposure levels and skin reactivity to German cockroach (Blattella germanica) in Croatia.

AIM To evaluate German cockroach (Blattella germanica) allergen levels in house dust and skin reactivity to German cockroach in adult atopic and non-atopic subjects in inland areas of Croatia. METHODS Blattella germanica group 2 (Bla g 2) allergen was measured using the enzyme-linked immunosorbent assay (ELISA) on test strips (Dustscreen(TM) test, Heska AG, Switzerland) in 94 house dust samples collected from living room and bedroom floors, 35 from rural and 59 from urban areas. Skin prick testing with common inhalatory allergens, Blatella germanica, storage mites Lepidoglyphus destructor and Tyrophagus putrescentiae (ALK-Abello, Denmark) was performed in 187 adult outpatients, 131 from urban and 56 from rural areas. Total serum IgE levels were measured using the ELISA method. Subjects with relevant respiratory and/or skin symptoms, at least one positive skin prick test, and/or increased total IgE were considered atopic. RESULTS Positive skin prick test to cockroach was observed in 18/187 subjects (9.6%). The frequency of skin prick test positive subjects to cockroach was higher in atopic than in non-atopic subjects, but not significantly (12.2% vs. 4.7%; p=0.098). Of 15 atopic subjects with positive skin prick test to cockroach, 14 also had positive skin prick test to storage mites, 8 to house dust mites, 1 to pollens, and none to cockroach only. Positive skin prick test to storage mites was the only factor which significantly increased the risk for having positive skin prick test to cockroach (n=187; odds ratio, 109.82; 95% confidence interval, 2.06- 5853.5; p= 0.020). In all 94 house dust samples, Bla g 2 was not detectable. CONCLUSIONS Our results suggest that there is no relevant exposure to cockroach allergen in house dust samples from inland areas of Croatia. Consequently, positive skin prick test to cockroach is rare in adult subjects, even in atopics. Positive skin prick test to cockroach in atopics is in the majority of cases related to positive skin prick test to storage mites, probably due to cross-reactivity.