Establishing IMMULITE^® 2000 cut‐off values for serum allergen‐specific immunoglobulin and exploring their relationship to exhaled nitric oxide

Abstract

AimPaediatric cut-off values for serum allergen-specific IgE (sIgE) using the Siemens IMMULITE® 2000 system to diagnose allergic rhinoconjunctivitis have not been established. We aimed to determine cut-off levels for sIgE for 10 common inhalant allergens and to study the relationship between sIgE, total IgE and fractional exhaled nitric oxide (FENO).MethodsWe enrolled 243 schoolchildren, including 164 with allergic rhinoconjunctivitis. Parental interviews, skin prick tests, sIgE, total IgE, FENO measurements, spirometry and exercise tests were performed.ResultsCut-off values with the best combined sensitivity and specificity were above the detection limit of the assay for seven of the ten allergens (0.23–1.1 kU/L). The overall accuracy of the IMMULITE® in detecting allergic rhinoconjunctivitis was good. sIgE was superior to total IgE and FENO in predicting allergic rhinoconjunctivitis to timothy, birch, mugwort, cat, dog and house dust mite. FENO was elevated in children with allergic rhinoconjunctivitis, irrespective of asthma.ConclusionCut-off values for sIgE were dependent on the allergic phenotype and were above the IMMULITE® detection limit for seven of ten inhalant allergens. Consequently, using the detection limit for sIgE as the decision point would result in over-diagnosing allergic rhinoconjunctivitis. When measuring elevated FENO in children, allergic rhinoconjunctivitis should be suspected.

Validation of a questionnaire against clinical assessment in the diagnosis of asthma in school children

“…Baseline FeNO was significantly higher in asthmatic than in non-asthmatic children, in line with findings from other studies (26,27). This is probably caused by a higher proportion of asthmatic children suffering from AR (17). Hence clinical testing, while essential both in the diagnosis of asthma and in clinical management of current asthma, is less important as an epidemiological tool.…”

Lower respiratory tract infections appear to be the most important risk factor for current asthma in subarctic schoolchildren

“…In addition to a second questionnaire, a structured interview and clinical examination, spirometry, exercise treadmill testing (EIB test), SPTs, measurements of exhaled nitrogen oxide (FE NO ), sIgE and total IgE were obtained, a process described in detail elsewhere . The participants were examined at least two weeks after any suspected respiratory tract infection during the school term from March 2009 to June 2010.…”