The value of a single skin prick testing for specific IgE Dermatophagoides pteronyssinus to distinguish atopy from non-atopic asthmatic children in the tropics.

In a tropical setting, where the prevalence of house dust mites (Dermatophagoides pteronyssinus) is high, we examined the advantage of a single battery of skin prick testing (SPT) for mite as a diagnostic tool by comparing the results of radio-allergo-sorbent-test (RAST) to distinguish allergic from non-allergic asthma in children. Fifty asthmatic children were enrolled in this study. After questioning the parents, SPT were carried out using house dust mite (D. pteronyssinus) and other 9 common aero-allergens and blood were taken for measuring the total IgE (PRIST) and specific IgE for mite (RAST). Dust was obtained from 14 asthmatic children's houses and mite counting was done under a high power microscope. With a daily temperature of 27.0 +/- 0.5 degrees C and a relative humidity of 80 +/- 1%, house dust mites were found in all samples; and 81% of the allergic asthmatic children had positive SPT for D. pteronyssinus. SPT for D. pteronyssinus had a sensitivity of 95% and specificity of 52% using RAST as gold standard and there was a moderate positive correlation between the size of SPT wheals and RAST scores for D. pteronyssinus (r = 0.67 and p = 0.001). The findings of this study suggest that SPT for mites should be used as a screening test and positive SPT should be confirmed by RAST.