Reference values of total serum IgE and their significance in the diagnosis of allergy in Asian children: PATCH study

[[abstract]]Background: Total serum immunoglobulin (IgE) test is usually performed to aid in the diagnosis of allergic diseases. Reference values of total IgE may vary among people of different ethnic backgrounds. This study aimed to establish reference values of total IgE levels in Asian children and to assess the significance of these values in the diagnosis of allergic sensitisation and allergic diseases. Methods: A total of 1321 Asian children aged 5– 18 years from the Prediction of Allergies in Taiwanese CHildren (PATCH) study, a population-based cohort, were evaluated for total and specific IgE levels by ImmunoCAP and ImmunoCAP Phadiatop Infant, respectively. Results: The geometric mean total IgE was significantly higher for children with allergic sensitisation than those without (239.5 vs 27.5 kU/l, P < 0.001), and for boys than girls (112.8 vs 74.4 kU/l, P < 0.001). Multivariate regression analysis revealed that allergic sensitisation was the single most important independent variable explaining variability of total IgE levels in this population. The area under the receiver-operator characteristic (ROC) curve of total IgE for diagnosing allergic sensitisation, asthma, allergic rhinitis and atopic dermatitis were 0.92, 0.72, 0.70 and 0.70, respectively. The sensitivity, specificity, and positive (PPV) and negative predictive values (NPV) of total IgE at the opitmal cut-off of 77.7 kU/l on the ROC curve for diagnosing allergic sensitisation were 82.3%, 87.1%, 89.5%, and 78.6%, respectively; whereas the corresponding values using the upper 95% CI of total IgE levels (164.3 kU/l) in children without allergic sensitisation were 61.2%, 95.0%, 94.3%, and 64.6%, respectively. Conclusion: Total serum IgE test discriminates Asian children with and without allergic sensitisation independent of allergic symptoms, with an optimal cutoff of 77.7 kU/l. This study confirms the insufficient diagnostic accuracy of total IgE levels alone to detect allergic diseases