Sensitization to local dust-mite fauna in Singapore.

BACKGROUND: Recent studies showed the presence of a unique dust-mite fauna in the indoor environment of Singapore. Immediate hypersensitivity to these dust mites, along with other known indoor allergens, may play a role in the pathogenesis of allergic respiratory diseases. This study evaluated the sensitization rates of the local atopic population to these allergens.

METHODS: The skin prick test was performed on a total of 391 individuals (289 patients with asthma and/or allergic rhinitis and 102 healthy controls) using extracts of six species of local dust mites (Austroglycyphagus malaysiensis, Blomia tropicalis, Dermatophagoides pteronyssinus, D. farinae, Sturnophagoides brasiliensis, and Tyrophagus putrescentiae) and 10 other common indoor allergens. Total serum IgE and specific IgE to these dust mites were also quantified with the fluorescence allergosorbent test (FAST).

RESULTS: The sensitization rates among patients with asthma and/or allergic rhinitis to dust mites and other inhalant allergens tested (via skin prick tests) were as follow: B. tropicalis (96.2%), D. pteronyssinus (93.4%), D. farinae (92.3%), A. malaysiensis (78.2%), S. brasiliensis (71.6%), T. putrescentiae (71.3%), canary feathers (69.9%), Periplaneta americana (cockroach) (59.5%), Blattella germanica (cockroach) (56.4%), mosquito (Aedes sp.) (46.4%), dog epithelia (mixed breed) (34.3%), kapok seed (31.8%), cat hair (29.1%), Aspergillus fumigatus (20.8%), Penicillium notatum (18.0%), and Candida (Monilia) albicans (9.3%). All patients were observed to react to at least three of the six dust-mite extracts, with 254/289 (87.9%) reacting to at least five or to all six. Skin prick responses to the dust mites were found to correlate with the corresponding specific IgE levels quantified by FAST (P<0.001). In addition, specific IgE levels to D. pteronyssinus and D. farinae were highly correlated (Spearman's rank coefficient = 0.76, P<0.001), as were those to B. tropicalis and A. malaysiensis (r = 0.60, P<0.001).

CONCLUSIONS: Asthma and/or allergic rhinitis patients were highly sensitized to the local dust-mite fauna. Thus, these dust mites should be considered important allergenic sources of this region.