When Allergy Tests Disagree: Landmark Study Reveals Hidden Gaps in Multiplex IgE Panels

A sweeping retrospective analysis of nearly 20,000 patients has revealed a striking and previously unmeasured problem in modern allergy diagnostics: when laboratories measure immunoglobulin E (IgE) antibodies against both crude allergen extracts and purified molecular components in the same test, the two approaches often tell strikingly different stories. The study, published in the British Journal of Biomedical Science, is the first to systematically compare extract-based and component-based results across a broad range of allergen sources within a single multiplex panel, and its findings could reshape how clinicians interpret allergy test reports worldwide.

The research, led by Hyejin Ryu of Seegene Medical Foundation and Kuenyoul Park of Hanyang University College of Medicine in Seoul, analysed deduplicated results from a high-volume referral laboratory over a two-month period in 2025. The team used the PROTIA Allergy-Q 192D panel, a multiplex enzyme immunoassay approved by the Korean Ministry of Food and Drug Safety in 2024, which simultaneously measures specific IgE against 29 crude extract allergens and 48 component allergens from a single small serum sample. In total, 19,949 patients with suspected allergic diseases were included, making this one of the largest real-world cohorts ever assembled to examine the concordance between these two fundamentally different diagnostic philosophies.

The distinction between crude extracts and component allergens is central to understanding why the results matter. Crude extracts contain the full mixture of proteins derived from an allergen source—whether house dust mite, birch pollen, shrimp, or cow’s milk—and have long been the backbone of in vitro allergy testing. Component-resolved diagnostics, by contrast, measures IgE against individual purified or recombinant proteins, allowing clinicians to distinguish genuine primary sensitisation from cross-reactivity driven by structurally similar molecules. Multiplex platforms that combine both approaches in a single run are a recent development, and until now, no study had systematically quantified how often the two methods agree or disagree when applied to the same patient samples.

The demographic profile of the cohort reflected the epidemiology of allergic disease in Korea. The median age was 33 years, with 28.6 percent of patients under 18 and 12.6 percent aged 65 or older. Females comprised 54.4 percent of the study population, consistent with previous reports that allergic disease prevalence and healthcare utilisation are higher in adult women. The vast majority of tests—83.7 percent—were requested by outpatient clinics, and nearly 89 percent of specimens came from the Seoul Metropolitan Area, reflecting the referral laboratory’s geographic catchment.

Positivity rates revealed the allergens driving allergic disease in this population. Among crude extracts, Dermatophagoides farinae, the American house dust mite, topped the list at 31.8 percent, followed closely by Dermatophagoides pteronyssinus, the European house dust mite, at 29.9 percent. Cat epithelium and dander registered 12.2 percent, birch pollen 10.4 percent, and shrimp 10.0 percent. Among component allergens, rDer f 2—the major allergenic protein of D. farinae—showed the highest positivity at 24.2 percent, followed by rFel d 1 from cat at 11.6 percent and rBet v 1 from birch pollen at 9.1 percent. These figures align with previous Korean studies reporting that 40 to 60 percent of patients with respiratory allergies are sensitised to house dust mites and that mite allergens are found in more than 90 percent of Korean households.

But the real story emerged when the researchers calculated agreement between paired crude extract and component results. Overall percent agreement exceeded 90 percent for most allergen pairs, yet this headline number masked a critical nuance: it was driven overwhelmingly by concordant negative results. When the team focused on positive percent agreement—how often a positive crude extract result was matched by positivity in at least one corresponding component—the picture changed dramatically. Positive agreement ranged from a high of 92.1 percent for birch pollen down to a mere 0.1 percent for plantain, revealing that for some allergen sources, the two test modalities provide almost entirely non-overlapping information.

Cohen’s kappa coefficient, a statistical measure that corrects for chance agreement, painted an even starker picture. Birch pollen achieved almost perfect agreement with its major component rBet v 1 (κ = 0.939), and cat dander with rFel d 1 (κ = 0.900), confirming these as reliable marker allergens where component testing adds genuine interpretive value. Dog dander, D. farinae, peach, oak, hazelnut, alder, egg white, and pork all showed substantial agreement (κ ≥ 0.6). But eight allergens—including D. pteronyssinus, apple, milk, olive, buckwheat, sycamore, Hevea latex, and plantain—showed very poor agreement (κ < 0.1). For D. pteronyssinus, the discordance was particularly dramatic: while the crude extract was positive in 29.9 percent of patients, the corresponding component rDer p 10 was positive in only 0.9 percent, meaning that among patients with positive crude extract results, more than 90 percent showed negative component results.

The biological explanations for these discrepancies are multifaceted. Cross-reactive carbohydrate determinants, or CCDs, are N-glycan structures found in plant- and insect-derived allergens that can trigger false-positive IgE reactions in up to 30 percent of patients without causing clinically significant allergic symptoms. Pan-allergens such as profilin, a ubiquitous plant protein, can similarly generate positive crude extract results that do not translate to component positivity. In other cases, the discordance reflects genuine gaps in panel coverage: shrimp sensitisation, for example, is mediated not only by the tropomyosin rPen a 1 (which showed only 0.6 percent positivity despite 10.0 percent crude extract positivity) but also by arginine kinase and sarcoplasmic calcium-binding protein, neither of which is included in the current panel. Similarly, milk allergy involves highly diverse IgE responses to multiple proteins—α-lactalbumin, β-lactoglobulin, and casein—each of which showed remarkably low positivity rates (0.1 to 0.2 percent) despite a crude extract positivity rate of 6.9 percent.

The house dust mite story illustrates the complexity particularly well. Der f 2, the major allergen of D. farinae, induces IgE responses in more than 70 percent of sensitised patients, explaining its high concordance with crude extract. By contrast, Der p 10, the tropomyosin component of D. pteronyssinus, is a minor allergen that triggers IgE in only about 7 to 15 percent of mite-allergic patients. It is included in panels not because it is a dominant sensitising agent but because it is a well-known cross-reactive allergen shared across invertebrates—including shrimp and other crustaceans—meaning its detection can signal broader cross-reactivity rather than primary mite allergy. The researchers suggest that laboratory reports should include interpretive comments when Der p 10 is positive, flagging its cross-reactive nature for clinicians.

The study’s implications extend beyond the Korean context. Component-resolved diagnostics offers genuine clinical advantages: patients positive for both peanut extract and the storage protein Ara h 2 face a high risk of systemic reactions, whereas those positive only for Ara h 8—a PR-10 protein homologous to Bet v 1—are likely to experience only mild oral allergy syndrome. Risk stratification of this kind directly informs decisions about oral food challenges, immunotherapy candidacy, and dietary counselling. But the new findings make clear that the value of component testing depends heavily on the specific allergen in question. For birch, cat, and D. farinae, component results provide robust confirmation of crude extract findings. For shrimp, milk, apple, and several pollen species, the two approaches diverge so substantially that clinicians must integrate both results with the patient’s clinical history rather than relying on either in isolation.

The authors acknowledge several limitations. The retrospective design precluded confirmatory testing with skin prick tests or oral food challenges, making it impossible to determine whether discordant results arose from false-positive crude extract reactions or false-negative component results. The cohort was heavily concentrated in the Seoul Metropolitan Area, and the allergen positivity profile reflects Korean and East Asian exposure patterns that may not generalise to other populations. Notably, some major component allergens—including Der p 1, Der p 23, and Ara h 6—were absent from the panel, which may partly account for the low concordance observed for certain sources. The concordance estimates were also calculated at a single positivity threshold of class 2 or higher (≥0.70 IU/mL), and different cutoffs could shift the results.

Nevertheless, the scale and systematic nature of the analysis make it a landmark reference for laboratory medicine. As multiplex allergy panels incorporating both crude extracts and molecular components become increasingly common—driven by their efficiency, small sample requirements, and ability to distinguish primary sensitisation from cross-reactivity—the need for allergen-specific interpretation guidelines becomes urgent. This study provides the first comprehensive baseline for that effort, demonstrating that a one-size-fits-all approach to reading combined extract and component results is neither scientifically defensible nor clinically safe. The authors call for further research linking serological concordance data to clinical outcomes such as symptom history and challenge test results, a step that would transform these laboratory observations into actionable clinical guidance.

Subject of Research: Diagnostic concordance between crude extract and component allergen specific IgE testing in multiplex allergy panels

Article Title: Concordance between crude extract and component allergens in a multiple allergen simultaneous test: a large-scale retrospective analysis

Article References: Ryu, H., Park, K., Kim, K., & Minn, D. (2026). Concordance between crude extract and component allergens in a multiple allergen simultaneous test: a large-scale retrospective analysis. British Journal of Biomedical Science, 83, Article 16596. https://doi.org/10.3389/bjbs.2026.16596

Image Credits: AI Generated

DOI: 10.3389/bjbs.2026.16596

Keywords: allergy diagnostics, component-resolved diagnostics, specific IgE, multiplex immunoassay, crude allergen extracts, house dust mite, Cohen's kappa, cross-reactivity, PROTIA 192D, allergen components, clinical laboratory, retrospective study