ImmunoCAP Phadiatop Infant: A New Blood Test for Detecting IgE Sensitisation in Children at 2 Years of Age

Abstract

Ballardini N, Nilsson C, Nilsson M, Lilja G. Allergy. 2006;61:337–343 PURPOSE OF THE STUDY. To evaluate the efficacy of a blood test, Phadiatop Infant (PI), in determining immunoglobulin E (IgE) sensitization to food and aeroallergens in children at 2 years of age. STUDY POPULATION. Prospective study of 239 children followed from birth. Families were recruited during pregnancy. For 75% of the participants, 1 or both parents had a history of atopic disease. METHODS. Clinical evaluation occurred every 6 months through 2 years of age. At 2 years of age, all children underwent skin-prick testing (SPT), allergen-specific IgE testing to a panel of common food and aeroallergens, and the PI blood test. Subjects with ≥1 positive SPT and allergen-specific IgE test were as categorized IgE sensitized. Those with either ≥1 positive SPT or ≥1 positive allergen-specific IgE were labeled as inconclusive. Those with all negative tests were considered non–IgE sensitized. Cutoff for a positive PI test result was >0.35 kU/L. RESULTS. On the basis of SPT and allergen-specific IgE tests, 26 (11%) of the 239 children were considered IgE sensitized, 182 (76%) were non–IgE sensitized, and 31 (13%) were labeled inconclusive. Using SPT and allergen-specific IgE tests as a reference, in the IgE-sensitized and non–IgE-sensitized groups, the sensitivity of the PI test was 96%, specificity was 98%, positive predictive value (PPV) was 89%, and negative predictive value (NPV) was 99%. When children with any positive SPT or allergen-specific IgE test (ie, the inconclusive group) were included, sensitivity was 82%, specificity was 98%, PPV was 94%, and NPV was 95%. There was a statistically significant association between any clinical symptom of atopic disease and a positive PI test result (odds ratio: 2.7; 95% confidence interval: 1.3–5.5). CONCLUSIONS. The ability of PI used as an independent test to detect IgE sensitization in young children seems to be a reliable alternative to SPT or allergen-specific IgE antibody testing. REVIEWER COMMENTS. As the prevalence of atopic diseases in the population increases, early identification of IgE-sensitized, atopic children is desirable. The PI test seems to be a reasonable alternative that does not require the placement of SPT or the selection of specific antigens for SPT or blood tests. In this study, the correlation of the PI test with SPT or blood-test results was good. The correlation with clinical symptoms was not quite as convincing. In terms of individual allergic symptoms, a positive PI test result only correlated significantly with eczema. This was probably limited by the fact that children were only followed up to age 2, when asthma and rhinoconjunctivitis are more frequently infection related than allergic.