Skin reactivity and specific IgE levels in the evaluation of allergic sensitivity to common allergens for epidemiological purposes

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Abstract
An investigation was conducted to test the validity of the skin-prick test (SPT) with eleven common allergens (Lofarma series proposed by Italian National Research Council for epidemiological studies) as a method for predicting the presence of specific antibodies in serum. The relationship between SPT, evaluated by two different methods (MWD = mean weal diameter, AHWR = allergen histamine weal ratio), and specific IgE levels (RAST) has been investigated in 101 patients tested consecutively for suspected allergic disease. Sensitivity, specificity and overall efficiency were assessed for different criteria of SPT positivity (.gtoreq. 4 mm or .gtoreq. 5 mm using MWD; ++ or +++ using AHWR). For pollens and moulds, a weal diameter .gtoreq. 5 mm gave better results than 4 mm, whereas for mites a MWD .gtoreq. 4 mm showed a better sensitivity and overall efficiency than 5 mm. Danders showed low sensitivity when either 5 or 4 mm criterion was considered. AHWR evaluation gave no better results, except for animal danders. Correlation coefficients between weal size and RAST class showed a good relationship for mites and pollens using both methods of SPT evaluation; a moderate relationship was observed with MWD criterion for moulds and with AHWR for danders. We conclude that a weal diameter .gtoreq. 5 mm can be assumed to predict RAST positivity for pollens and moulds, and for mites, a weal .gtoreq. 4 mm can be a more accurate criterion. The poor correlation between weal diameter and RAST positivity for such allergens as animal danders and moulds suggest that in these cases SPT should be associated to specific serum IgE evaluation to prove allergic sensitivity.