Diagnostic Test for IgE Sensitization

Both SPT and sIgE tests (Table 17.4) are reliable and validated to detect IgE-mediated sensitization to food allergens, but cannot be used as the sole tests for clinical allergy diagnosis [9]. One reason for this is false positives. This refers to positive SPT or sIgE test results, but where there are no symptoms or signs of FA when exposed to the specific food allergen. Such individuals do not have FA and it is therefore recommended that the clinical history should always guide diagnostic testing. Testing for large panels of food allergens should be discouraged as false positive SPT or sIgE results may lead to unnecessary dietary elimination and nutritional inadequacies [2, 3]. False negative results are another problem. Accordingly, negative SPT or sIgE results combined with a strong clinical history suggesting FA should be interpreted with caution and warrant further investigation [8]. False negative SPT or sIgE results may, for instance, be possible due to the commercial test extract not containing the relevant allergen found in the raw food [8]. SPT tests are often preferred over sIgE tests due to their lower costs and near instant results [8]. SIgE testing should be used when SPT is contraindicated or ineffective [3].