In vitro diagnosis of allergy: how to interpret IgE antibody results in clinical practice

Abstract

SummaryThe basis of any diagnosis of allergy requires a good history and examination, which should then provide a certain degree of confidence as to whether or not allergy is present. However, the diagnosis cannot be confirmed on the basis of symptoms alone, because both allergic and non-allergic conditions can present with similar symptoms. Based on prevalence figures, about half of the patients presenting with allergic symptoms in primary care may be non-allergic. Therefore, allergy testing in the form of specific IgE (sIgE) measurement and/or skin prick testing is an invaluable aid in demonstrating both the presence and severity of such an allergy. The usefulness of such tests extends beyond just the positive or negative result. Often, more information can be gleaned by using the test results in a form of a continuous variable in order to determine the likelihood that allergy can be attributed as an explanation for patients' symptoms and disease. In this review, we describe the rationale for utilising specific IgE antibody tests in diagnosing allergy. Furthermore, to optimize the information gained from allergy testing, we describe how to employ one particular well-validated IgE testing system for determining the likelihood that an individual patient's disease can be attributed to allergy.

Allergic Rhinitis and its Impact on Asthma (ARIA) 2008*

“…However, small wheals induced by prick tests and positive results of intradermal tests with concentrated extracts are less frequently associated with the detection of serum-specific IgE (56, 1369). Moreover, low levels of serum-specific IgE are less often associated with symptoms than higher levels, but they do not exclude allergic symptoms (1243,1370). Correlations between responses to skin tests or serum-specific IgE and nasal challenges are less consistent because of the nonspecific hyperreactivity.…”

“…), arbitrary units (RAST class, PRU/ml) or units of IgE (IU/ml, KU/l). However, it is advisable to use a quantitative measurement (1242,1243 (1244). The different reagents are critical for an appropriate assay (for review see Ref.…”

Chemiluminescent Assay Versus Immunoblotting for Detection of Positive Reaction to Allergens

“…Measurement of allergen-specific IgE is a useful tool for identifying the sources of allergic reactions. 7,8 Since its introduction, MAST-CLA has been widely used as a screening test for allergic diseases. However, it has been criticized as having no clear cutoff levels, variable sensitivity and specificity, and a lengthy testing time.…”

Chinese Guideline on allergen immunotherapy for allergic rhinitis

“…Consequently, serum sIgE tests are of great importance in the diagnosis of allergic diseases. Normally, low levels of serum sIgE are less likely to produce symptoms than higher levels, but this is not the case with allergic symptoms (176), particularly in very young children. Serum sIgE antibody tests are particularly helpful when the SPTs are negative and there is a high clinical suspicion for AR (177,178).…”