Comparison of Three Multiple Allergen Simultaneous Tests: RIDA Allergy Screen, MAST Optigen, and Polycheck Allergy

We compared the performances of 3 Multiple Allergen Simultaneous Test (MAST) assays: RIDA Allergy Screen (R-Biopharm, Darmstadt, Germany), MAST Optigen allergy system (Hitachi Chemical Diagnostics, Mountain View, CA), and Polycheck Allergy (Biocheck GmbH, Munster, Germany). Forty sera that tested positive with the RIDA Allergy Screen (20 for food and 20 for inhalant panel) were subjected to MAST Optigen and Polycheck Allergy. For 26 available sera with discrepant results, 62 ImmunoCAP allergen-specific IgE tests (Pharmacia Diagnostics, Uppsala, Sweden) were performed. Percent agreements (kappa value) were 87.6% (0.59) and 91.3% (0.60) between RIDA and MAST; 89.9% (0.55) and 88.3% (0.46) between RIDA and Polycheck; and 86.8% (0.51) and 90.6% (0.61) between MAST and Polycheck. Compared with ImmunoCAP, agreements (kappa value) of inhalant and food panels were 51.7% (0.04) and 33.3% (−0.38) for RIDA; 60.7% (0.27) and 81.8% (0.59) for MAST; and 65.5% (0.26) and 45.5% (0.07) for Polycheck. The agreements between RIDA, MAST, and Polycheck and ImmunoCAP-positivity were 45.7%, 88.2%, and 28.6%, respectively, and the agreements for ImmunoCAP-negativity were 37.0%, 51.9%, and 88.9%. MAST Optigen showed better agreement with ImmunoCAP than other assays in the food panel. Better sensitivity of MAST Optigen and better specificity of Polycheck Allergy were suspected.


Introduction
For the diagnosis of allergy, presence of allergen-speci�c immunoglobulin E (IgE) is usually established either by in vivo allergen skin tests or by in vitro allergen-speci�c IgE measurements [1,2]. Although, in vivo skin test has been widely used to detect allergen-speci�c IgE. It is not a quantitative test and is difficult to be standardized [3]. erefore, detection of allergen-speci�c IgE is important for the diagnosis of allergy [1,2]. Since the development and improvement of �uorescent enzyme immunoassay, the ImmunoCAP system (Pharmacia Diagnostics AB, Uppsala, Sweden) has been widely accepted as a reference method of allergen-speci�c IgE measurement because of its reliability, reproducibility, and good accordance with allergen skin test. However, individual ImmunoCAP test can only detect IgE against a single allergen, making it quite expensive to use in a clinical setting [4]. erefore, several multiple allergen simultaneous tests (MAST) were developed, which can detect more than 30 allergen-speci�c IgE [5][6][7][8]. However, allergen-speci�c IgE assays are o�en modi�ed as manufacturers improve allergens or change reagents to optimize test performance, affecting the diagnostic performance of those assays. MAST Optigen (Hitachi Chemical Diagnostics, Mountain View, CA, USA), upgraded version of MAST CLA (Hitachi Chemical Diagnostics, Mountain View, CA, USA), and Polycheck Allergy (Biocheck GmbH, Munster, Germany) were recently introduced with good performances [6,9,10]. However, to the best of our knowledge, comparison of performances of those assays and analysis of concordance with ImmunoCAP system has not been performed. e aim of this study was to compare the performance of 3 MAST assays: RIDA Allergy Screen (R-Biopharm, Darmstadt, Germany), MAST Optigen allergy system (Hitachi Chemical Diagnostics, Mountain View, CA, USA), and Polycheck Allergy (Biocheck GmbH, Munster, Germany) compared to ImmunoCAP system as a reference method.  food panels which contain 39 kinds of allergens. Aer 45 min of incubation at room temperature and wash, 250 uL of Biotin tagged anti-IgE were added. Aer 45 minutes of incubation at room temperature and wash, 250 uL of streptavidin conjugate were added. Twenty minutes of incubation at room temperature and wash, 250 uL of luminescent reagent were added. Aer 20 minutes of incubation, results were scanned with CCD camera (RIDA X-Screen Reader) and interpreted as class 0-6. Class ≥1 was interpreted as positive.

Polycheck Allergy.
Aer washing of inhalant and food cassette which contain 39 kinds of allergens, 250 uL of start solution were added. Aer 60 seconds of incubation, 200 uL of patient sera were added. Aer 1 hour of incubation on shaker, 6 times of washes were performed. Anti-IgE was added and 45 minutes of incubation on shaker was performed. Aer 3 times of washes, 250 uL of enzyme tagged conjugate were added. Aer 20 minutes of incubation and washes, 250 uL of luminescent reagent were added. Aer 20 minutes of incubation, results were scanned and interpreted with Biocheck Image Soware as class 0-6. Class ≥1 was interpreted as positive.

MAST Optigen.
Patient sera were added to MASTpette chambers which contain 35 kinds of allergens. Aer 2 hours of incubation and washes, enzyme-tagged anti-IgE was added. Aer 2 hours of incubation and washes, luminescent reagent was added. Aer 10 minutes of incubation, results were interpreted as class 0-4 with MAST Optigen luminometer. Class ≥1 was interpreted as positive.  [11]. We calculated three different agreement percentages (positive, negative, and total agreement percentage). e positive and negative agreement percentages were calculated with the proportions of agreement for the average of their positive and negative responses. e total agreement percentage was calculated following: (total number of results − number of discrepancies) × 100/total number of results [12].

Discussion
Although, most of evaluations of performance of MAST assays were performed compared to allergen skin test [6,[13][14][15][16], comparisons with ImmunoCAP assay have been performed [5,8,17] considering the limitation of allergen skin test as a reference method due to the difference of principle of in vivo test from in vitro test [1]. ImmunoCAP assay has been known to have established performance [2]. Our study was also performed compared to ImmunoCAP assay. In this study, 3 MAST assays showed moderate agreement (86.8-91.3%, kappa 0.46-0.61) among them ( Table 2). In comparison with ImmunoCAP, three MAST assays showed similar agreements for Inhalant panel (51.7-65.5%, kappa 0.04-0.27), and MAST Optigen showed better agreement (81.8%, kappa 0.59) than Polycheck Allergy (45.5%, kappa 0.07) or RIDA Allergy Screen (33.3%, kappa −0.38) for food panel (Table 4). In previous reports, the agreement between RIDA Allergy Screen and ImmunoCAP has been reported as 29.1% (kappa −0.303) on 633 discrepant sera between RIDA Allergy Screen and another MAST assay, AdvanSure system (LG Life Science, Seoul, Korea) [8]. Among 115 allergic patients, RIDA Allergy Screen showed 83.1% of agreement with ImmunoCAP for 10 common allergens [17]. Our result is similar to former one [8] because we also performed ImmunoCAP assays only on sera with discrepant results among three MAST assays.
In our study, the agreement of MAST Optigen with ImmunoCAP-positive results was best (91.7% for inhalant panel and 86.4% for food panel) among 3 MAST assays (Table 5), implicating better sensitivity than other two assays. MAST CLA, previous version of MAST Optigen, has been reported to have slightly lower sensitivity (44.5%) than RIDA Allergy Screen (55.8%) or Polycheck Allergy (55.6%) [6]. e performance of MAST Optigen might be improved compared to MAST CLA as previous report [17].
e agreement of Polycheck Allergy with ImmunoCAPnegative results was best (93.8% for inhalant panel and 81.8% for food panel) among 3 MAST assays, implicating better speci�city than other two assays (Table 5). Polycheck Allergy has been reported to have similar speci�city (93.5%) with an RIDA Allergy Screen (90.0%) or MAST CLA (96.0%) [6]. In our study, ImmunoCAP assay was performed only on discrepant sera, which could make some different results from previous study [6].
For individual allergens, on House dust, which is most common allergen in Korean population [7] and on Peach, which showed most common discrepant results in our study, better sensitivities of MAST Optigen were suspected (Table 4). From previous study, when compared to allergen skin test, MAST CLA showed best performance on D. farinae [6]. However, because of the retrospective design of our study, the small number of ImmunoCAP assay results due to shortage of residual sera is a limitation to see the performance of MAST assays on individual allergens. Further studies are needed on larger number of samples to compare the performance of MAST assays on individual allergens.

Conclusions
e 3 MAST assays: RIDA Allergy Screen, MAST Optigen, and Polycheck Allergy showed moderate agreements among them. In comparison with ImmunoCAP allergen-speci�c Ig� test, MAST Optigen showed better agreement than other assays in the food panel. Better sensitivity of MAST Optigen and better speci�city of Polycheck Allergy were suspected. Further studies are needed in larger number of samples to know the performance of MAST assays for individual allergens.