The Indirect Basophil Activation Test Is a Safe, Reliable, and Accessible Tool to Diagnose a Peanut Allergy in Children.

BACKGROUND: The gold standard for the diagnosis of a peanut allergy is an oral food challenge (OFC), but it is a time-consuming, patient-unfriendly, and expensive test. The in vitro direct basophil activation test (BAT) for peanuts was shown to be a promising diagnostic tool for replacing the OFC. OBJECTIVE: To determine the diagnostic accuracy of the indirect (passive) BAT. Compared with the direct BAT, the timing of the indirect BAT is more flexible, and the problem of nonresponding basophils (unresponsive to IgE receptor-mediated signaling) is circumvented. METHODS: In 74 children, suspected of peanut allergy and eligible for an OFC, indirect BAT results for peanut extract, Ara h2, and Ara h6 were compared with the results of a double-blind placebo-controlled food challenge. The reactivity and sensitivity of the basophils in the BAT were correlated to both the allergy status and the threshold dose in the OFC. RESULTS: The combined basophil reactivity for Ara h2 and Ara h6 showed the highest accuracy (94%) for the diagnosis of a peanut allergy, with positive and negative predictive values of 96% and 89%, respectively. The sensitivity of the basophils for Ara h2 significantly discriminates between patients who tolerated up to 0.4 g of peanut protein in the OFC and those who did not. CONCLUSIONS: Because the indirect BAT showed a high diagnostic accuracy for peanut allergy, it is a promising alternative to the classical direct BAT and could lead to a reduction in OFC use.

The Basophil Activation Test reduces the need for a food challenge test in children suspected of IgE-mediated cow's milk allergy.

BACKGROUND: The gold standard for the diagnosis of cow's milk allergy is the Double-Blind Placebo-Controlled Food Challenge (DBPCFC) test. However, disadvantages of the DBPCFC are the potential risk of anaphylactic reactions, the time-consuming procedure and high costs. OBJECTIVE: The aim of this study was to determine the reliability of the Basophil Activation Test (BAT) both for the initial diagnosis of cow's milk allergy in children and for the determination of tolerance in children with cow's milk allergy. METHODS: Ninety-seven BATs and cow's milk-specific IgE (sIgE) tests were performed in 86 infants/young children, suspected of (persistent) cow's milk allergy, who were qualified for an in-hospital DBPCFC. The BAT was performed with cow's milk extract and the purified major allergens casein, α-lactalbumin, ß-lactoglubulin. Basophil activation was determined by CD63 upregulation measured by flow cytometry. The BAT results were compared to the DBPCFC outcomes. RESULTS: Based on unequivocal DBPCFC and BAT result combinations (80%), the BAT had a sensitivity and specificity of 100% (CI: 86%-100% and 68%-100%, respectively) in IgE-sensitized children (41% of the tested children). All non-IgE-sensitized children (59%) had a negative DBPCFC and BAT, except for five patients. These latter showed delayed and relatively mild symptoms in the DBPCFC with a negative BAT, supporting a non-IgE-mediated allergy in these children. CONCLUSIONS AND CLINICAL RELEVANCE: The BAT seems reliable and cost-effective to diagnose patients with an IgE-mediated cow's milk allergy. In IgE-sensitized patients, a BAT might replace a DBPCFC. For non-IgE-sensitized patients presenting with mild symptoms, we propose to consider a (double-blind) extended (time) challenge test at home.

An alternative inhibition method for determining cross-reactive allergens.

BACKGROUND: Inhibition assays are an useful tool to identify the allergen of primary sensitization of cross-reactive allergens. Classical ELISA-based inhibition assays are limited by both the availability of commercial standardized allergen extracts and the experience and knowledge needed for making home-made extracts. Moreover the direct comparison of the inhibition ELISAs outcomes between different laboratories is difficult because of different sources of used allergen extracts and a number of methodological variations. Therefore, we propose a novel ImmunoCap (Phadia, Thermofisher Scientific) based immunoinhibition method with the use of commercially available Caps as the allergen source. METHODS: The novel ImmunoCap based immunoinhibition method was developed and tested with sera from patients with a well-known cross-reactive sensitization for fig (Ficus carica) and ficus (Ficus benjamina). Results were compared with a classically applied inhibition method, i.e. addition of homemade allergen extract to patient serum. RESULTS: The amount of allergens (fig and ficus extracts) needed to reach a similar degree of inhibition was comparable for both inhibition methods. CONCLUSIONS: The ImmunoCap based inhibition assay, in addition to classical inhibition methods, is a valuable tool as the ImmunoCap analyzer and commercial allergens (Caps) are more widely available which makes the outcomes of inhibition tests comparable between different laboratories. Furthermore, in the ImmunoCap inhibition method the same protein source is used for both the inhibition of sIgE and sIgE measurement, which might be even more relevant when multiple cross-reactive allergens are tested.

Diagnostic reference range of κ/λ free light chain ratio to screen for Bence Jones proteinuria is not significantly influenced by GFR.

OBJECTIVES: The aim of our study was to analyse whether the κ/λ free light chain ratio reference range for screening for Bence Jones proteinuria should be dependent on the estimated glomerular filtration rate (eGFR). METHODS: The serum κ/λ free light chain ratio, eGFR, serum M-protein and Bence Jones protein were measured in 544 patients for whom Bence Jones protein analysis was ordered. RESULTS: In the population of patients without Bence Jones proteinuria or a M-protein (n = 402), there is no gradual increase in κ/λ free light chain ratio with diminishing eGFR. The κ/λ free light chain ratio in this group was 0.56-1.86 (95% interval). With this diagnostic reference range of the κ/λ ratio, 105 of the 110 patients with Bence Jones protein could be identified correctly. Only five patients with Bence Jones proteinuria (<0.17 g/L) were missed, without diagnostic or therapeutic consequences. In 36 patients (6.6%), an abnormal κ/λ free light chain ratio was measured without the presence of Bence Jones proteinuria. CONCLUSIONS: A κ/λ free light chain ratio in serum can be used safely and efficiently to select urine samples which should be analysed for Bence Jones proteinuria with an electrophoresis/immunofixation technique. Using this diagnostic reference range, the number of urine samples which should be analysed by electrophoresis/immunofixation could be reduced by 74%. The diagnostic reference interval can be determined best in a group of patients for whom Bence Jones analysis is indicated. For calculation of this reference range, the eGFR value does not need to be taken into account.