Original article Predictors of response to bronchial allergen challenge in 5- to 6-year-old atopic children Bronchial allergen challenge is predominantly a research tool used to examine the patho-physiological events associated with allergen exposure in the airways (1–5) and which may be rarely employed to confirm bronchial sensitization to a specific allergen in symptomatic indi- viduals with a suggestive clinical history (6). A positive response to bronchial allergen challenge, defined by a fall in forced expiratory volume in one second (FEV 1 ), is considered indicative of the presence of Ôbronchial allergyÕ in the individual. It is well recognized that response to bronchial allergen challenge in adults and older children with asthma may be predicted to varying extent by the degree of sensiti- zation expressed as wheal size or circulating immuno- globulin E (IgE) levels (6–13). However, the relationship between bronchial allergy and atopy in young children remains poorly understood. In particular, there are currently no studies that explore the relationship between bronchial allergy and immune markers of atopy or clinical characteristics in young children in whom the diagnosis of atopic asthma has not been established, and whose wheeze prognosis is uncertain. The aim of this study was to examine the relationship between response to bronchial allergen challenge, inten- sity of atopic sensitization and presence of other clinical characteristics traditionally associated with allergic dis- ease in a group of 5- to 6-year-old atopic children deemed at high risk of developing asthma and allergy. Methods Subjects Subjects for the present study were recruited from a highly char- acterized birth cohort of 198 children at high risk of developing Background: The relationship between atopy and bronchial allergy in young children is not completely understood. Objective: To examine the association between response to bronchial allergen challenge, immune markers of atopy and other clinical characteristics in 5- to 6- year-old children. Methods: Children with positive skin test (SPT) to aeroallergen, together with a proportion of SPT negative children (as controls), were recruited from a birth cohort of 198 children at high risk of developing atopic disease and underwent allergen challenge. Results: Thirty-seven children (26 atopic and 11 SPT negative), median age 74.5 months, were challenged: 31 with house dust mite and six with grass allergen. Only atopic children responded to challenge: n ¼ 12/26 (46%). Wheal size [odds ratio (OR) 2.5 (1.2–5.3), P ¼ 0.01], allergen-specific immunoglobulin E (IgE) [OR 3.4 (1.23–9.61), P ¼ 0.02], total IgE [OR 8.6 (1.1–68.7), P ¼ 0.04], current wheeze [OR 12 (1.7–81.7), P ¼ 0.006] and persistent eczema [OR 11.0 (1.7–68.3), P ¼ 0.006] emerged as the strongest independent predictors of re- sponse to allergen challenge. Prediction of response to allergen challenge was significantly improved when immune markers of atopy, and in particular wheal size, were combined with clinical characteristics. Conclusion: The relationship between atopy and bronchial allergy is quantitative at this age. There may be potential to create more powerful indicators of the presence of respiratory allergy in young children when immunological markers of atopy are considered quantitatively and when combined with clinical history of coexistent allergic disease. T. A. Douglas 1,2 , M. Kusel 1 , E. M. Pascoe 2 , R. K. S. Loh 2 , P. G. Holt 1 , P. D. Sly 1,2 1 Division of Clinical Sciences, Telethon Institute for Child Research, Centre for Child Health Research, The University of Western Australia; 2 Princess Margaret Hospital for Children & King Edward Memorial Hospital for Women, Perth, WA, Australia Key words: allergens; asthma; atopy; bronchial allergen challenge; childreneczema; immunologic tests; paediatric; wheeze. Dr Tonia A. Douglas Telethon Institute for Child Health Research Centre for Child Health Research University of Western Australia Perth 6008 WA Australia Accepted for publication 19 December 2006 Abbreviations: AR, allergic rhino-conjunctivitis; CI, confidence interval; Der P 1, dermatophagoides pteronyssinus antigen; EAR, early asthmatic response; FEV 1 , forced expiratory volume in one second; HDM, house dust mite; IgE, immunoglobulin E; LAR, late asthmatic response; OR, odds ratio; PC 20 FEV 1 , provocation con- centration of allergen causing a 20% fall in FEV 1 ; SD, standard deviation; SPT, skin prick test. Allergy 2007: 62: 401–407 Ó 2007 The Authors Journal compilation Ó 2007 Blackwell Munksgaard DOI: 10.1111/j.1398-9995.2007.01329.x 401