Accuracy of ImmunoCAP Rapid in the diagnosis of allergic sensitization in children between 1 and 14 years with recurrent wheezing: the IReNE study

Abstract

It is estimated that at least one out of three children with recurrent wheezing is atopic. Reliable diagnostic tools are needed in primary care that allow for adequate identification of these children. The purpose of this study was to assess the value of ImmunoCAP Rapid (ICR) Wheeze-Rhinitis Child in the identification of atopy with the use of 10 selected allergens in children with recurrent episodes of wheezing. A multicenter population study is based on primary care. It included children managed consecutively at the health center, who had three or more episodes of wheezing, at least one of them in the last 12 months. Each child completed a physical examination, an epidemiological survey, one capillary blood sampling (110 microl) for ICR, and one venous blood sampling for determination of Phadiatop Infant, total IgE and 10 specific IgE measurements. The children were identified as atopic, based on their clinical signs and symptoms and at least one positive specific IgE (0.35 kU(A)/l or higher), before knowing the results of ICR, Phadiatop Infant and total IgE. ICR was read by two independent observers. Six classes were evaluated, negative without any color and five positive degrees of pink-red color. Two hundred and fifteen children aged between 1 and 14 years were studied (138 boys); 50.7% were identified as atopic, 39.1% were sensitized only to inhalant allergens, 6.5% to food allergens and 5.1% to both. The predominant allergen was the dust mite (39.3%). For ICR, there were 2134 valid double observations. The Kappa index, comparing the negative results vs. any positive result, was 0.91 (95% CI: 0.88-0.94). The intraclass correlation coefficient was 0.98 (95% CI: 0.98-0.99). In the identification of a child as atopic, the positive post-test probability of ICR depended on the color degrees considered: 88.4% for any positive and 97.6% for the most intense tones. The positive post-test probability of Phadiatop Infant and total IgE was 95.6% and 68.2% respectively. ICR showed good reliability for the most prevalent allergen, the dust mite, with a sensitivity of 90.5% (95% CI: 82.1-95.8) and specificity of 88.5% (95% CI: 81.7-93.4). The analysis of the other allergens was limited by the small number of sensitized children. The analysis of receiver operating characteristic curves revealed an area under the curve of 0.84 (95% CI 0.80-0.88) for the cut-off point of specific IgE of 0.35 kU(A)/l and of 0.94(CI 0.91-0.97) for 2 kU(A)/l. A greater intensity of color of the lines of ICR was related to higher levels of specific IgE in blood. ICR is a reliable test for the identification of atopy in children, which identifies most children as atopic, and shows a good correlation in allergen-by-allergen identification. This suggests that it should be regarded as a first-rate tool, in the primary care clinic, for the evaluation of children with recurrent wheezing.