Comparison between RAST and Pharmacia CAP system: a new automated specific IgE assay

RAST represents the standard technique to titrate serum-specific IgE and was found to have a higher efficiency in the diagnosis of IgE-mediated allergy than other in vitro tests. Pharmacia CAP system (CAP) is a new solid-phase immunoassay, fully automated, used for the titration of specific IgE antibodies. Results are listed in kilounits per liter, equilibrated against the World Health Organization standard for IgE. RAST and CAP were compared in 106 unselected patients (6 to 59 years) characterized by a detailed clinical history and skin prick tests with standardized allergen extracts. IgE to cat, Dermatophagoides pteronyssinus, Alternaria, orchard grass, olive, and Parietaria pollen were tested; 470 tests were run. The specificity, sensitivity, and efficiency of both in vitro tests ranged from 85.5% to 100% except for olive pollen, in which the sensitivity of both in vitro tests was low (68.2% for the new test and 63.6% for RAST). Except for orchard-grass pollen, the sensitivity and specificity of CAP were better than that of RAST. There was a highly significant correlation between both tests (r range, between 0.864 to 0.987). CAP competes favorably with RAST and has the advantage of being automated and eliciting results in kilounits per liter.     

Clinical evaluation of CAP System and RAST in the measurement of specific IgE

We investigated the diagnostic value of a new in vitro test, Pharmacia CAP System (Pharmacia Diagnostics AB, Uppsala, Sweden), for the quantitative measurement of allergen-specific IgE antibodies by comparison with RAST in 2 groups of patients, 71 atopic and 48 non-atopic. In the last 20 years RAST has supplied a good diagnostic tool, but this test presents some problems, the main one being sensitivity. The new test has a solid phase able to bind even very small amounts of specific IgE and an anti-IgE tracer with very low cross-reactivity with other immunoglobulins, thus presenting more favourable conditions. From the analysis of our results, Pharmacia CAP System gave higher sensitivity (94% compared to 88% of RAST) with no loss of specificity (96% for both tests). The reliability of these results is ensured by the proper selection of patients who were all suffering from pollinosis and were clinically diagnosed as certainly hypersensitive to a single pollen. A positive trend was found between severity of asthma and levels of specific IgE for timothy. Pharmacia CAP System appears to identify a larger number of atopic patients than RAST.     

Evaluation of the value of 2 methods for measuring levels of allergen specific IgE antibodies in serum--Phadebas RAST I immuno CAP System

Two diagnostics sets Pharmacia--Phadebas RAST and Immuno CAP System determining the concentration of specific IgE antibodies in blood serum were compared with each other and with skin prick tests (SPT). Two common alergens--Dermatophagoides pteronyssinus and Dermatophagoides farinae were evaluated. Analysis of ROC curves shows that maximum specificity and sensitivity was obtained when the cut off value of RAST and CAP reached to 4.9 PRU/ml and 7.3 kU/l respectively. Our date shows the good correlation between RAST,CAP and SPT.     

Clinical evaluation of a new enzymo-assay for allergen-specific IgE

A new assay for the determination of specific IgE in serum, using a monoclonal anti-IgE (Stallerzym), was evaluated. Compared with the results of skin prick tests, the Stallerzym was found to be 93% specific and 73% sensitive. In sera from patients selected to be either clearly allergic or not allergic (as defined by the concordant results of case history, skin prick test, and provocation test), Stallerzym proved to be as accurate and reliable as the Phadezym IgE RAST currently available.     

Automated specific IgE assay with recombinant allergens: evaluation of the recombinant Aspergillus fumigatus allergen I in the Pharmacia CAP System

Background We report the results of a study comparing the recombinant Aspergiilus fumigatus allergen I (rAsp f I) to commercial A. jumigatus extracts in serological assays, Pharmacia CAP System and skin tests. Objective The study was designed to test the feasibility of using recombinant allergens in an automated serology system for determination of allergen-specific IgE. Methods Patients with allergic bronchopulmonary aspergillosis (ABPA), asthmatics with A. fumigatus allergy and control subjects, who included allergic asthmatics without allergy to A. fumigatus and healthy subjects, were investigated. All subjects were characterized with respect to their total IgE level, radio allergosorbent test to A. fumigatus and skin test reactivity to both commercial A. fumigatus extracts and recombinant rAsp f I protein. Results All patients with ABPA (n = 30) showed positive skin test reactions with commercial A. fumigatus extracts, and 24 were sensitized to r Asp f I by the same criterion. The 10 patients with asthma and A. fumigatus allergy showed positive skin reactions to at least one commercial extract, and five reacted to r Asp f I. AU control subjects (H= 19) scored negatively in skin tests to A. fumigatus extracts and r Asp f I, and showed no detectable rAsp f I-specific IgE. ImmunoCAP carrying immobilized r Asp f I were evaluated using sera from all individuals described and the results compared with those obtained with the r Asp f I-specific ELISA for IgE. The data obtained with the two r Asp f I-specific detection systems correlated closely (r= 0.997) and were in perfect agreement with the skin test results. Conclusion The data show that r Asp f I can be used as immobilized allergen in the Pharmacia CAP System indicating the feasibility of using recombinant allergens for an automated serological diagnosis of allergic diseases. However, every recombinant allergen needs to be evaluated individually for its performance if applied to a new diagnostic technology.     

An IgE inhibition assay for the detection of allergen specific IgE

A method for the detection of specific IgE in human serum is described, using a modified radioimmune assay termed the Inhibition Assay Technique (IAT) The technique is based on the ability of specific IgE to bind with allergen. The difference in total IgE before incubation with the allergen and after incubation with the allergen gives a relative concentration of specific IgE to that particular allergenic substance. The assay has been shown to correlate with both the intradermal skin test as well as the standard RAST now used to determine specific IgE.     

Study on specific IgE antibodies in pediatric allergic patients by CAP system

The CAP system is a new method to detect specific IgE antibodies and is an advanced method of the traditional paper disc RAST. Our result suggests a significant correlation between scores obtained with the CAP system and those with the traditional RAST. Since specific IgE antibodies against multiple allergens can be measured with the CAP system, we studied 5 food allergen specific IgE antibodies (Fx5) in cases of infantile atopic dermatitis. This study indicates a good correlation between the Fx5 scores and clinical symptoms of these patients. Thus, it is concluded that the CAP system is useful for screening IgE antibodies against multiple food allergens in cases of infantile atopic dermatitis.     

Evaluation of new system for the detection of IgE antibodies (CAP) in atopic diseases

An evaluation of a newly developed IgE antibody assay system (CAP) was carried out. There was a clear correlation between IgE antibody titers measured by CAP single and RAST (= 0.642 to 0.979). It turned out that CAP single is more sensitive than RAST and non-specific adsorption of IgE immunoglobulin to the solid phase was assumed to be less in CAP than in RAST. Pathogenic allergens diagnosed either clinically or by in vitro assay systems were compared. The sensitivity and specificity of the CAP system were 94.2% and 87.3%, respectively. CAP multi which binds groups of multiple allergens on the solid phase, was examined for the screening of hypersensitivity to categories of allergens. Statistical sensitivities of CAP multi resided between 63.9% to 86.2%, while the specificities were 98% to 100%, indicating that CAP multi is useful for the exploration of causative allergens. Phadiatop, which fixes multiple inhalant allergens, showed a sensitivity of 89.6%. The specificity of phadiatop was 93.9%, when examined for intrinsic bronchial asthma patients, and 91.2% for normal subjects indicating that phadiatop is more useful than total IgE measurement for the screening of atopic trait.     

Evaluation of Oriton IgE, a new kit for measurement of allergen specific IgE antibodies]

To determine whether Oriton IgE kit, a new kit for the measurement of allergen-specific IgE antibodies, is useful in screening allergen-specific antibody, we measured the titers of IgE antibodies against 11 different allergens (house dust 2, Dermatophagoides farinae, Japanese cedar, ragweed pollen, egg white, milk, cat epithelium, dog epithelium, Candida, Alternaria and Aspergillus) with the Oriton IgE kit, and the results were compared to those of intradermal tests and RAST in 103 allergic patients and 10 normal subjects. There was a clear correlation between IgE antibody titers measured by the Oriton IgE kit and the RAST. The correlation coefficient was 0.76 (p less than 0.01) and the total correspondence rate was 85.9%. We also found strong correlation between the Oriton IgE kit and RAST in IgE antibody titer against 5 different allergens, Dermatophagoides farinae, Japanese cedar, ragweed pollen, egg white and Candida. The correlation coefficient was over 0.70. The correspondence rate, sensitivity and specificity of the Oriton IgE kit to intradermal tests was 71.8%, 45.3% and 87.8% respectively. The sensitivity of the Oriton IgE kit was slightly higher, while the specificity was slightly higher in RAST, although the differences were not statistically significant between these methods. Correspondence rate of the Oriton IgE kit was similar to that of RAST. These results suggested that the Oriton IgE kit is useful in screening allergen specific IgE antibodies.     

Comparison of a new specific IgE assay Quidel allergy screen to skin prick test, intradermal test, and RAST

Quidel Allergy Screen (QAS), an enzyme-linked immunosorbent assay, has been developed for measuring IgE antibodies against 9 allergens (HD 1, HD 2, Mite 1, Mite 2, Japanese cedar, ragweed, cat dander, sweet vernal grass, and egg white) at the same time. To determine whether this assay is useful in screening allergen-specific IgE antibody, we compared the titers of IgE antibodies against the 9 allergens measured by QAS to the obtained in skin prick tests, in intradermal tests and by RAST in 93 atopic asthmatics and 25 normal subjects. We found a good agreement between the reactivity of skin prick tests and the reactivity of QAS. There was a significant correlation between the threshold doses of intradermal tests and the titers of QAS. We also found a good agreement between the reactivity of RAST and the reactivity of QAS, and a strong correlation between the titers of RAST and the titers of QAS. Thus, it is concluded that QAS is useful in screening IgE antibodies against multiple allergens simultaneously.     

A rast assay for monitoring specific IgE antibodies in the mouse

Mouse monoclonal anti-ovalbumin IgE was isolated from serum of BALB/c mice implanted with the IgE secreting hybridoma (14–205).Purified IgE was used to immunize rabbits and for the preparation of an antiserum specific for mouse IgE. The latter was used to develop a RAST assay to replace the PCA technique in monitoring antigen-specific IgE responses in the mouse.     

Development of the Abbott MATRIX Aero assay for the measurement of specific IgE.

An enzyme immunoassay has been developed for the quantitation of specific immunoglobulin E (IgE) in human serum to a panel of allergens. The assay system, called the Abbott MATRIX Aero, includes an instrument, reagents and test cell disposables. Each test cell contains fourteen airborne allergens individually localized on a nitrocellulose solid phase. Individual calibration curves for each allergen are established by the manufacturer and included in barcode form with each test kit. Stable factory calibration eliminates the need to establish a calibration curve with each assay run. The instrument automatically incubates, washes, and reads the test cell and prints each result, which ensures assay reproducibility and provides ease-of-use. Analysis of test results shows good agreement with another in vitro assay for specific IgE. The Abbott MATRIX Aero is a sensitive, reproducible and easy-to-use system for the measurement of specific IgE to a panel of fourteen allergens simultaneously using a single, small volume of serum.     

Clinical evaluation of a type III secretion system real-time PCR assay for diagnosing melioidosis

A Burkholderia pseudomallei type III secretion system real-time PCR assay was evaluated on clinical specimens in a region where melioidosis is endemic. The PCR was positive in 30/33 (91%) patients with culture-confirmed melioidosis. All six patients with melioidosis septic shock were blood PCR positive, suggesting potential for rapid diagnosis and commencement of appropriate therapy.     

Comparison of VIDAS Stallertest and Pharmacia CAP assays for detection of specific IgE antibodies in allergic children

In vitro determination of specific IgE antibodies in serum is the most frequently used method, besides the skin test, for diagnosing allergies. Standardized and reproducible assays of specific IgE antibodies contribute to the quality of diagnosis and treatment of allergic disease. This study compared the results and performance characteristics of the Pharmacia CAP system and a new specific IgE method using the VIDAS Stallertest (manufactured by bioMériux). To evaluate their clinical efficiency, the results of the CAP and VIDAS Stallertest assays were compared with skin prick test (SPT) results. After allergic patients completed SPTs, serum samples were collected and CAP and VIDAS Stallertest assays were performed to determine specific IgEs for Dermatophagoides farinae, D. pteronyssinus, cockroach, and alternaria. For egg and milk, we measured only the correlation between the 2 in vitro assays. When SPT was used as a reference standard, the sensitivity and specificity of the CAP assay was a little higher in respect to all inhalant allergens. There were significant correlations between the results of VIDAS Stallertest and CAP assays for IgE antibodies to inhalant and food allergens. This study indicates that the VIDAS Stallertest and Pharmacia CAP assays are feasible and replicable for measuring allergen-specific IgE.     

Clinical significance of specific IgE to common allergens

Serological measurements of specific IgE to Dermatophagoides farinae, D. pteronyssinus and grass pollen showed statistically highly significant correlations with prick test reactions, the sizes of weals elicited, nasal tests and the clinical history. In subjects with negative prick tests, intracutaneous tests gave reactions which were not associated with specific IgE or reactions to nasal tests. Highly significant correlations were also found between total IgE values and prick test reactions to the allergens tested and to 48/80 but not to histamine; there was a negative correlation with reactions to anti-IgE serum. The reactions to prick tests identified almost all subjects with specific IgE.     

Evaluation of specific IgE to the recombinant group 2 mite allergens Lep d 2 and Tyr p 2 in the Pharmacia CAP system.

BACKGROUND: Several recombinant allergens have been shown to be potentially useful for diagnosis of IgE-mediated allergy, but only a few recombinant allergens are at present commercially available in serological assays for detection of specific IgE. The aim of this study was to evaluate the IgE binding to the recombinant major dust mite allergens rLep d 2 and rTyr p 2 and compare it with the IgE binding to the commercial mite extracts Lepidoglyphus destructor and Tyrophagus putrescentiae in the Pharmacia RAST CAP System. METHODS: The recombinant allergens rLep d 2 and rTyr p 2 were immobilised on ImmunoCAPs, and sera from 461 Swedish farmers who are frequently exposed to mites were analysed for specific IgE antibodies. Immunoblotting was performed to evaluate discrepancies between the results obtained with the recombinant and the commercial CAP assays. RESULTS: The IgE values of each recombinant assay significantly correlated with the IgE values of the corresponding commercial CAP assay. The sensitivity of the rLep d 2 assay was 73.3% and that of the rTyr p 2 assay, 60.5% of that provided by the commercial L. destructor and T. putrescentiae assays. Two subjects out of 416, who tested negative in the commercial L. destructor assay, were positive to rLep d 2. The corresponding figures for rTyr p 2 and the T. putrescentiae extract were 5/418. The possibility that these subjects were sensitised to L. destructor and T. putrescentiae could not be excluded. CONCLUSIONS: The data suggest that it may be possible to use rLep d 2 and rTyr p 2 on ImmunoCAPs to detect and quantify IgE antibodies to these, the major allergens of L. destructor and T. putrescentiae. It appears likely that the addition of just a few more recombinant L. destructor and T. putrescentiae allergens in the CAP assay will be sufficient for in vitro diagnosis of IgE mediated allergy to L. destructor and T. putrescentiae.     

A new method to bind allergens for the measurement of specific IgE antibodies

BACKGROUND: Detection of allergen-specific IgE antibodies in patients' sera plays a key role for the diagnosis of IgE-mediated allergy. If no validated test system is available, diagnostic tools must be developed, usually by coupling or binding the allergens to a solid phase. Streptavidin ImmunoCAP is a new solid phase for binding of allergens which can be used in the Pharmacia CAP system. OBJECTIVE: It was the aim of this study to assess the diagnostic validity of Streptavidin ImmunoCAP. METHODS: Biotinylation and allergen concentration for binding to Streptavidin ImmunoCAP were optimized and IgE obtained with natural rubber latex, obeche wood, wheat and rye flour Streptavidin ImmunoCAP were compared with the results of ImmunoCAP and Enzyme Allergo-Sorbent Test (EAST) using sera from patients complaining of workplace-related respiratory symptoms. RESULTS: While the relation of biotin-label and protein was critical (best results were obtained with a 5- fold molar excess), labelled protein for coupling to streptavidin ImmunoCAP was applicable in a wide concentration range. On average, IgE values with streptavidin ImmunoCAP were as high as with ImmunoCAP but considerably higher than values obtained by EAST. CONCLUSION: Streptavidin ImmunoCAP is a valuable tool for sensitive and specific measurement of IgE binding to new allergens superior to cellulose disk-based methods.