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IgE antibodies in human onchocerciasis. Application of a newly developed radioallergosorbent test (RAST).

A radioallergosorbent test (RAST) was developed to detect IgE antibodies against adult Onchocerca volvulus antigens coupled to CnBr-activated Sepharose. Twenty-four out of 25 (96%) onchocerciasis sera were reactive. The lower limit of sensitivity was estimated to be at approx. 3 ng/ml IgE antibodies. Tests of sera from patients with non-filarial helminth infections showed much less cross-reactivity with RAST than with an enzyme-linked immunosorbent assay (ELISA) detecting IgG and IgM antibodies against the same antigen preparation. At a specificity comparable to that of RAST, the sensitivity of ELISA was only 61%. A heterologous antigen, prepared from female Dipetalonema viteae worms, was comparatively evaluated with O. volvulus. In RAST and ELISA, onchocerciasis sera were less reactive than against the O. volvulus antigen. Since sera from patients with non-filarial helminth infections were more reactive in RAST and almost equally reactive in ELISA using the D. viteae antigen, sensitivity was 83% for RAST and only 22% for ELISA (compared at the specificity identical to that of the O. volvulus RAST).

Animals↗

Comparison of a new type of skin test (Phazet) with existing skin test methods and the radioallergosorbent test (RAST).

A new skin test method (Phazet) for diagnosis of immediate-type allergic disease was tested in 232 patients attending the Guy's Hospital Allergy Clinic, and compared with conventional skin test methods, using Bencard and Pharmalgen allergen solutions, and with serum IgE antibody tests (RAST). Six allergens (cat, dust mite, Cladosporium, grass pollen birch pollen and plantain pollen) were used, as well as histamine and a negative control. Phazet proved easy to use and was popular with inexperienced operators (medical and dental students). For the majority of allergens there was reasonably good agreement with the different tests, but overall Phazet and RAST produced fewer positive results than the other skin tests methods. In particular, the frequency of positive histamine tests was lower with Phazet (82%) than with Bencard or Pharmalgen (99%), but this discrepancy was lower in the second part of the study when the minimum time for the insertion of the needle (1 sec) was more scrupulously observed. Phazet offers a convenient and practical alternative to conventional 'wet' skin test methods.

Allergens↗

Correlation of modified radioallergosorbent test scores and skin test results.

In addition to a significantly increased sensitivity as compared with the initial Phadebas radioallergosorbent test, a major advantage of the Fadal-Nalebuff modified RAST is its correlation with skin testing using skin end point titration. This correlation allows physicians to use both these modalities in the diagnosis and treatment of allergic disorders. However, it has been anecdotally believed that the correlation of radioallergosorbent test classes and skin test end points varied somewhat with different antigens. Fifty-three patients were tested by radioallergosorbent test for 12 inhalant antigens common to the North Texas region. These patients subsequently underwent confirmation of their radioallergosorbent test results by application of intradermal tests at a concentration of one fivefold step weaker than the corresponding radioallergosorbent test level (a "RAST minus one" dilution). The relationship between radioallergosorbent test and skin test results will be critically analyzed.

Administration, Inhalation↗

Anaphylactic anaesthetic reactions. The value of paper radioallergosorbent tests for IgE antibodies to muscle relaxants and thiopentone.

The three currently available paper radioallergosorbent tests ('suxamethonium', alcuronium and thiopentone) were evaluated. 'Suxamethonium' radioallergosorbent test (which employs choline conjugated to paper discs) proved to be reliable in the detection of allergy to neuromuscular blockers, which were confirmed as the most common cause of anaphylactic reaction during general anaesthesia. Thiopentone radioallergosorbent test may also be useful, and is recommended in conjunction with 'suxamethonium' radioallergosorbent test in the preliminary investigation of reactions. Patients with positive 'suxamethonium' radioallergosorbent test usually require further testing, including alcuronium radioallergosorbent test, skin testing with a wide range of drug concentrations or leucocyte histamine release test.

Adolescent↗

Comparison of immediate intradermal test reactivity with serum IgE quantitation by use of a radioallergosorbent test and two ELISA in horses with and without atopy.

OBJECTIVE: To compare a radioallergosorbent test and 2 ELISA with intradermal testing for the determination of environmental allergen hypersensitivity in horses with and without atopic diseases. DESIGN: Prospective clinical study. ANIMALS: 10 horses with recurrent urticaria, 7 with atopic dermatitis, 16 with chronic obstructive pulmonary disease, and 22 without atopy. PROCEDURE: History, physical examination, hemogram, serum biochemical analyses, bronchoalveolar lavage, and an intradermal test (used as the criterion standard) with a regional panel of 73 allergens were performed in all horses. Serum was analyzed by use of the 3 in vitro assays of allergen-specific IgE. RESULTS: An ELISA based on the alpha chain of the high-affinity IgE receptor, the Fcepsilon receptor immunoglobin epsilon chain (FcepsilonRIalpha) for IgE, had the overall highest kappa statistic (0.238), positive predictive value (49%), and negative predictive value (78%). Overall agreement between the FcepsilonRIalpha-based ELISA and the intradermal test was fair. The highest kappa statistic was obtained by the FcepsilonRIalpha-based ELISA in horses with atopic dermatitis (0.330). Kappa statistics for the radioallergosorbent test and a polyclonal antibody-based ELISA agreed slightly with that of the intradermal test at best. CONCLUSIONS AND CLINICAL RELEVANCE: None of the 3 serum allergy tests reliably detected allergen hypersensitivity, compared with the intradermal test. The FcepsilonRIalpha-based ELISA performed significantly better overall than the other 2 tests. Low sensitivity of all 3 assays indicates the need for continued study to elucidate a more sensitive test for the determination of potentially pathogenic allergens in horses.

Animals↗

Value of a multiantigen radioallergosorbent test in diagnosing atopic disease in young children.

The purpose of this study was to investigate the value of a new multiantigen radioallergosorbent test, Phadiatop Paediatric, in the diagnosis of atopy in children less than 7 years of age. The diagnosis of atopic disease was established by history, physical examination, total serum IgE concentration, and the results of prick skin tests or radioallergosorbent tests or both, and then compared with the result of the Phadiatop Paediatric test for each patient. One hundred two patients (62 boys) between the ages of 4 months and 7.3 years were enrolled (median age 3.2 years). After the history and physical examination, 42% of the patients were believed to be atopic and 32% to be nonatopic; the diagnosis was uncertain in 26%. Skin prick test reactions to a variety of foods and inhalants were positive in 41 of 63 children tested; results of radioallergosorbent tests were positive in 35 of 61 children. Overall, atopy was diagnosed in 53 children and 49 were found to be nonatopic. When the clinical diagnosis was used as the gold standard, the Phadiatop test resulted in a correct diagnosis of atopy in 49 of 53 cases and of no atopy in 43 of 49 cases: sensitivity = 92%, specificity = 88%, and efficiency = 90%. Although the Phadiatop Paediatric test does not indicate specific sensitivities, it provides the clinician with a useful screening test for atopic disease in children 7 years of age or less, and the researcher with a means of validating atopic populations.

Child↗

The diagnosis of immediate type allergy to Cladosporium herbarum. Differences between extracts and the efficacy of radioallergosorbent test (RAST) assays.

The radioallergosorbent test (RAST) was used to demonstrate IgE antibodies to Cladosporium herbarum in 35 children. Freeze-dried samples of Cladosporium herbarum were obtained from two commercial products, extracted and used for the preparation of two rast disc series which were compared with the commercially available Phadebas Cladosporium herbarum discs. Marked qualitative differences were found.

Child↗

Comparison of methods of performing the radioallergosorbent test: Phadebas, Fadal-Nalebuff and Hoffman protocols.

A series of control, IgE myeloma containing and atopic sera were tested by the radioallergosorbent test using identical lots of commercially available reagents following three different RAST protocols: Phadebas, Fadal-Nalebuff and that used in our own laboratories. In addition, a new RAST tracer was evaluated in the Phadebas and Fadal-Nalebuff methods. The Phadebas technique, using the standard 0.35 PRU cut-off, was the least sensitive at 68% but its sensitivity was raised to 84% using an 0.14 PRU cut-off. The specificity was 100% at 0.35 and 95% at 0.14 PRU. Our laboratory's technique gave a sensitivity of 84% and a specificity of 100%. The Fadal-Nalebuff method had the highest sensitivity at 92% but the lowest specificity at 92%. The Fadal-Nalebuff technique leads to a significant number of false positive scores, particularly in sera with IgE > 500 U/ml or with RAST discs that have significant non-specific binding. The Fadal-Nalebuff method can be used reliably if modified to include suitable negative controls for each antigen tested.

Allergens↗

The radioallergosorbent test (RAST) for the serological diagnosis of human anisakiasis.

The serum of patients with parasitologically confirmed and one patient with a clinically presumptive case of anisakiasis were tested by the radioallergosorbent test (RAST) and counter-electrophoresis (CEP) for IgE and IgG antibodies, respectively, using antigens prepared from larval (L3) stage Anisakis simplex and larval (L2) stage Toxocara canis. All sera were RAST-positive to the A. simplex antigen and RAST-negative to the T. canis antigen. All sera were CEP-negative to both antigens. The presence of a specific IgE antibody suggests that the RAST could serve as a useful technique for the serodiagnosis of anisakiasis in man.

Adult↗

Lymphocyte transformation and radioallergosorbent tests in drug hypersensitivity.

An in-vitro lymphocyte transformation test was performed on 252 patients, some of whom were suspected to have hypersensitivities to antibiotics, aspirin, methyldopa, allopurinol, or halothane. Overall, the proportion of patients with clinically documented drug reactions who had positive tests was higher than the corresponding proportion of patients without such reactions. When results from individual drugs were compared, however, significant differences were found only with respect to antibiotics and aspirin. Extent of lymphocytic transformation did not correlate with severity or form of hypersensitivity. A radioallergosorbent test for penicillin-binding IgG and IgE was done on plasmas of 63 patients whose lymphocytes were tested against penicillin in the lymphocytic transformation test. The radioallergosorbent test and the lymphocyte transformation test results did not correlate, but levels of penicillin-binding IgG and IgE showed significant correlation. A greater number of patients with clinical hypersensitivity to penicillin had positive results by both the lymphocyte transformation test and the radioallergosorbent test than by either test alone. The clinical relevances of these tests are discussed.

Allopurinol↗

Skin and radioallergosorbent tests in patients with sensitivity to bee and wasp venom.

Intradermal (ID) and prick tests with bee or wasp venom (Pharmalgen) have been performed on 102 subjects with a history of adverse reactions to stings and forty-six control subjects giving no such history. Venom was diluted 100, 10 and 1 microgram/ml for prick testing and 10(-2), 10(-2), 10(-3) and 10(-4) micrograms/ml for ID injections. In forty-six control subjects all were tested with the highest concentration of prick testing solution (100 micrograms/ml), eight (17%) had positive reactions, a similar reaction rate to that reported in control subjects using 10(-1) micrograms/ml ID. In our 102 test subjects skin tests were therefore regarded as positive only if the reaction was elicited by 10 micrograms/ml or less by prick test of 10(-2) micrograms/ml or less ID. In general the results with skin prick tests and ID tests were comparable when the prick solution was 1000 times the concentration of that used for ID testing. ID tests were positive in thirteen with negative skin prick, seven of whom had detectable antibodies when tested by RAST. Conversely four with a positive skin prick test (two of whom were RAST positive) were considered negative on ID testing. As judged either by RAST or skin tests it appeared that sensitivity diminished with the time interval from the last sting (P less than 0.001).

Bee Venoms↗

Comparison of the radioallergosorbent test to intradermal skin testing in the diagnosis of stinging insect venom allergy.

RAST and skin tests were compared for five venoms in a group of 60 patients with histories of stinging insect allergy. Twelve patients were skin test negative to all venoms and also RAST negative. The 48 skin test positive patients gave an 88% correlation of RAST and skin test with 92% of the skin test positive patients RAST positive and 82% of the RAST positive patients skin test positive. If patients strongly positive to honey bee showing positive RAST to vespids with negative skin test were not counted, then 91% of the RAST positive patients were skin positive. The term "false" should not be used in relating RAST to skin test results without supporting challenge evidence.

Bee Venoms↗

Increased speed and sensitivity, and reduced sample size of a micro-radioallergosorbent test (MRAST).

Performance of the radioallergosorbent test (RAST) in small volumes (MRAST) increases the efficiency with which both IgE antibody and 125I-anti-IgE bind. The rate at which antibody binds is increased up to 290-fold so that the assay can be completed in 60 min with comparable sensitivity to RAST. The increased speed of binding is achieved by the use of small incubation volumes which does not affect the rate at which bound antibody is dissociated. The resulting change in the equilibrium in favour of antibody binding yields a 10-fold increase in sensitivity which makes it possible to use as little as 5 microliter of sample compared with 50 microliter which is normal for RAST. MRAST can be used to measure IgE antibody in heel prick blood samples taken from babies, in rat sera and in other situations where the sample is in short supply.

Allergens↗

A comparative study of skin tests and determination of the serum level of specific IgE immunoglobulins by means of the radioallergosorbent test in subjects with atopy.

On 73 patients suspected for atopic diseases, 258 skin tests and radioallergosorbent tests (RAST) for specific IgE in serum were carried out. The results of both tests were compared in connection with the clinical picture. A good qualitative positive correlation was found, especially for grass pollen and house dust. False positive results with RAST cannot be excluded. The RAST seems to be a valuable adjunct to extensive allergologic diagnostic investigation, particularly in cases where difficulties can be expected in the performance or the interpretation of skin tests.

Allergens↗

A modified technique for the radioallergosorbent test.

A modification of the radioallergosorbent test (RAST) is described utilizing a multiple automated sample harvester. The technique increases the efficiency of the procedure by shortening the time required for its performance. A study is reported in which this method is compared to that recommended by the manufacturer.

Absorption↗