A new framework for the interpretation of IgE sensitization tests

Abstract

IgE sensitization tests, such as skin prick testing and serum-specific IgE, have been used to diagnose IgE-mediated clinical allergy for many years. Their prime drawback is that they detect sensitization which is only loosely related to clinical allergy. Many patients therefore require provocation tests to make a definitive diagnosis; these are often expensive and potentially associated with severe reactions. The likelihood of clinical allergy can be semi-quantified from an IgE sensitization test results. This relationship varies though according to the patients' age, ethnicity, nature of the putative allergic reaction and coexisting clinical diseases such as eczema. The likelihood of clinical allergy can be more precisely estimated from an IgE sensitization test result, by taking into account the patient's presenting features (pretest probability). The presence of each of these patientspecific factors may mean that a patient is more or less likely to have clinical allergy with a given test result (post-test probability). We present two approaches to include pretest probabilities in the interpretation of results. These approaches are currently limited by a lack of data to allow us to derive pretest probabilities for diverse setting, regions and allergens. Also, cofactors, such as exercise, may be necessary for exposure to an allergen to result in an allergic reaction in specific IgE-positive patients. The diagnosis of IgE-mediated allergy is now being aided by the introduction of allergen component testing which may identify clinically relevant sensitization. Other approaches are in development with basophil activation testing being closest to clinical application.Allergy 71 (2016) 1540-1551

Making the Most of In Vitro Tests to Diagnose Food Allergy

“…The ultimate goal of the allergy test result is to determine the probability of clinical allergy; this is then used to decide whether an OFC is warranted 91 . The probability of clinical allergy depends first and foremost on the clinical history (Table V) and secondarily on the allergy test result (Tables I, III, and IV).…”

“…For example, if a patient consumes age-appropriate amounts of the food regularly without developing any symptoms, the probability of having FA is negligible regardless of the allergy test results; such patients should in fact not be tested as a false-positive result could be confusing for the patient and lead to unnecessary food avoidance. The clinical history provides information that enable the clinician to establish a pretest probability of FA that will be taken into account to determine the probability of clinical allergy for a given allergy test result, that is, the post-test probability 91 . This reasoning is best described using nomograms that use likelihood ratios to calculate the post-test probability based on a given pretest probability.…”

“…This reasoning is best described using nomograms that use likelihood ratios to calculate the post-test probability based on a given pretest probability. Likelihood ratios have the advantage of not depending on the prevalence of the disease in the population, as opposed to PPV, and can be calculated from the sensitivity and specificity of the test 91, 92, 93. Different factors can modulate pretest probabilities and likelihood ratios, for instance, the previous allergic reaction(s), the dietary history, age, ethnicity, concomitant atopic diseases, geographical location, and the clinical setting.…”

Challenges in the implementation of the EAACI AIT guidelines: A situational analysis of current provision of allergen immunotherapy

“…This would include the use and interpretation of tests used to confirm the presence of sensitization and whether or not this was relevant to the patients' clinical state. 46 Dialogue between specialist and PCPs should help to improve knowledge and treatment pathways at a local level. The issue of reimbursement of practitioners and patients needs to be recognized as these issues may affect the accessibility to AIT, including those related to travel and missing time from work.…”

“…31,50 Further work needs to be undertaken around the place and utility of specific-IgE in primary care and how best to educate practitioners in the interpretation of results in the clinical context. 46 This has been identified as a pressing research need by the IPCRG. 51 …”