Is there a role for immunoblots in the diagnosis of latex allergy? Intermethod comparison of in vitro and in vivo IgE assays in spina bifida patients

Challenge tests in the diagnosis of latex allergy

The aim of this study is to evaluate the sensitivity, specificity and safety of challenge tests and their usefulness in the diagnosis of latex allergy. Forty adult subjects (F/M = 34/6, aged 18-66 yrs) with a history of adverse reactions after latex exposure and positive prick test and/or specific IgE to latex were enrolled. They were compared with 20 control subjects. They underwent provocative (cutaneous, mucous-oral, sublingual, conjunctival, nasal, bronchial, vaginal) tests. Symptoms and drug scores were recorded for each patient during challenges. All patients reacted to at least one of the following: cutaneous, nasal and conjunctival tests. No systemic reactions requiring epinephrine occurred. Of the challenges, the vaginal test resulted as the safest, but it had low sensitivity and many limits related to the procedure. According to our data, bronchial and nasal tests had the highest sensitivity (76% and 82% respectively), and were more precise than other tests in determining latex exposure and symptoms, but the bronchial test also presented the highest rate of risk. Mucous and cutaneous tests resulted as the most reliable. For all the tests, specificity and positive predictive value were 100%. All control subjects resulted negative to all challenges. There were no statistically significant changes in skin and serologic tests between the first and second visits. Correlations between MIS and skin tests and between MIS and serum tests were not found. Challenges can be considered safe diagnostic procedures. Tests that most faithfully reproduce natural exposure, on the basis of a patient's history, are preferable.

Mediator release assay for assessment of biological potency of German cockroach allergen extracts

BACKGROUND

Cockroach is an important allergen in inner-city asthma. The diagnosis and treatment of cockroach allergy has been impeded by the lack of standardized cockroach extracts.

OBJECTIVE

We investigated the utility of a mediator release assay based on rat basophil leukemia (RBL) cells for comparing the potency of German cockroach extracts.

METHODS

RBL cells (line 2H3) transfected with human FcepsilonRI were passively sensitized with sera from subjects with cockroach allergy and stimulated with serial dilutions of 3 commercial cockroach extracts (1:10 weight/volume). In addition, the in-house prepared extract was tested in separate experiments with pooled sera that produced optimal performance in the RBL assay. N-hexosaminidase release (NHR) was used as a marker of RBL cell degranulation and was examined in relation to the intradermal skin test (ID(50)EAL) and serum cockroach-specific and total IgE levels.

RESULTS

The median cockroach-specific IgE concentration in 60 subjects was 0.72 kU(A)/L (interquartile range, 0.35-2.97 kU(A)/L); 19 sera (responders) produced a minimum 10% NHR to more than 1 extract. Responders had higher median cockroach-specific IgE (7.4 vs 1.0 kU(A)/L) and total IgE (429 vs 300 kU/L) levels than nonresponders. Ranking of extract potency was consistent between the mediator release assay and the ID(50)EAL. For the in-house prepared cockroach extract, the dose-response curves were shifted according to the concentration of the extract. NHR was reproducible between different experiments by using pooled sera.

CONCLUSION

The mediator release assay measures biologic potency and correlates with the ID(50)EAL. It should be further evaluated to determine whether it could be used to replace intradermal skin test titration for assessing the potency of cockroach extract.

Mediator release assays based on human or murine immunoglobulin E in allergen standardization

BACKGROUND

The biological potency of allergens can be measured by provoking mediator release from effector cells. As established immunochemical methods in allergen standardization only determine inhibition potency or major allergen content, routine tests for biological potency may enhance standardization and batch control of allergen products.

OBJECTIVE

The general performance and application potential of biological in vitro assays in batch control and standardization of allergens and as a tool for verifying activity and stability of allergen standards were analysed.

METHODS

Allergen extracts of five clinically relevant allergens from three to five different manufacturers were investigated. A CAP-IgE-inhibition assay was compared with mediator release assay (MRA)s based on murine or human basophils. Rat basophilic leukaemia (RBL) cells were passively sensitized with pooled murine allergen-specific IgE-containing sera. Humanized RBL cells and human-stripped basophils were sensitized with pooled patient's sera, which were also used for the CAP-IgE-inhibition assay. Allergen specificity of the sera was determined by immunoblotting.

RESULTS

A good batch-to-batch consistency was found with each assay among all manufacturers and allergens tested. Between different manufacturers, the products showed differences in activity and the various assays indicated an almost identical ranking. However, the biological assays revealed qualitative differences of biological activity or composition of allergen preparations undetectable by IgE-inhibition assay.

CONCLUSIONS

MRAs provide refined information on allergen activity, either confirming the results of IgE-inhibition assay, or indicating differences requiring further investigation, and represent a highly sensitive novel tool in allergen standardization. By using permanently cultivated cell lines, repeated venepuncture to obtain human basophils is avoided. As in the RBL assay, the coefficient of variation for the release values were below 15% and for the ED50 below 25%, the assay is suitable to determine differences that are relevant for batch control purposes.

Anaphylaxis during anesthesia: results of a 12-year survey at a French pediatric center

BACKGROUND

Following adverse reactions to anesthesia, tests are carried out to determine the mechanism of the reaction and to identify the agent responsible. No specific data are available in France concerning such skin tests in children.

METHODS

Between 1989 and 2001, we assessed hypersensitivity reactions to general anesthesia in 68 children. Thirty underwent more than one operation, for congenital malformations. Immunoglobulin (Ig)E-mediated anaphylaxis was diagnosed on skin tests combined with the clinical history.

RESULTS

Grade I, II and III reactions were observed in 20, 27 and 21 children, respectively. IgE-mediated anaphylaxis was diagnosed in 51 children: 31 (60.8%) for neuromuscular blocking agents (NMBA), 14 (27%) for latex, seven (14%) for colloids, five (9%) for opioids and six (12%) for hypnotics. Vecuronium was the NMBA causing the largest number of reactions. Cross reactivity to NMBA available in France was observed in 23 of 30 children (76%), particularly for vecuronium and atracurium or pancuronium. The estimated frequency of IgE mediated anaphylactic reactions was one in 2100 operations. Based on our results, 25 children subsequently received a different anesthetic with no adverse reaction.

CONCLUSIONS

As in adults, NMBA, then latex were responsible for most anaphylactic reactions during anesthesia. Our results confirm that skin tests with anesthetic agents are feasible and safe in children and improve the safety of subsequent anesthetic procedures.

Antigen characterization of major cork moulds in Suberosis (cork worker's pneumonitis) by immunoblotting

BACKGROUND

We characterized by immunoblotting the antigenicity of the most frequent fungi colonizing cork during its industrial processing, Penicillium glabrum and Chrysonilia sitophila. Penicillium glabrum is the main causative agent of Suberosis, a hypersensitivity pneumonitis of cork workers. Chrysonilia sitophila induces both IgE sensitization and occupational asthma in the wood processing industry.

METHODS

Serum-specific IgG, IgG4 and IgE to P. glabrum and C. sitophila from nine cork workers with hypersensitivity pneumonitis (HP) and seven with asthma (four with occupational asthma) were analysed by immunoblotting.

RESULTS

Both HP and asthmatic patients' sera showed immunoreactivity to several proteins resolved in the specific immunoblot strips. The frequency of specific IgG recognition to 12-13.5 and 33 kDa proteins of P. glabrum was significantly higher in HP patients. The sera of HP patients had significantly higher specific IgG recognition to 16 and 51-55 kDa proteins of C. sitophila. There was no specific IgE recognition in the sera of HP or asthmatic patients to both fungi.

CONCLUSIONS

Different patterns of antibody reactivity to P. glabrum and C. sitophila are seen in cork workers with hypersensitivity pneumonitis or asthma. The 12-13.5 and 33 kDa proteins of P. glabrum and the 16 and 51-55 kDa proteins of C. sitophila may be major antigens in Suberosis.

Role of cross-allergies to latex in clinical routine of anesthesia

STUDY OBJECTIVE

To determine the applicability and reliability of a screening questionnaire to detect patients at high-risk of latex allergy; to assess the importance of other allergies such as profilin allergies (pollinosis) for presence of latex sensitization; and to determine the clinical effectiveness of preemptive avoidance of latex exposure in high-risk patients.

DESIGN

Prospective, clinical trial.

SETTING

Operative theater of a university hospital.

PATIENTS

95 adult patients.

INTERVENTIONS

Patients were preoperatively screened and classified for present latex allergy (high-risk and low-risk group) according to a specially designed screening questionnaire. Anesthesia and surgery in the high-risk group were performed strictly avoiding latex-containing materials. The low-risk group (other allergies including pollinosis) received routine treatment, without latex-avoidance. Effects of latex avoidance or exposure were evaluated by measuring specific IgE titers perioperatively.

MEASUREMENTS AND MAIN RESULTS

According to the questionnaire, 45 patients at high risk were defined. Validity of classification of high-risk patients is supported by significantly higher total IgE and latex and grass profilin specific IgE compared to the low-risk group. There were no significant differences in other profilin-specific IgEs. In one case of severe anaphylactic reaction a drop of latex-specific IgE during surgery could be observed.

CONCLUSION

The questionnaire allowed the identification of most patients at high risk for latex allergy. In isolated pollinosis no changes in any specific IgE levels were detectable. Strict avoidance of perioperative latex exposure in high-risk patients increases safety during anesthesia and surgery.

Comparison of ammoniated and nonammoniated extracts in children with latex allergy

BACKGROUND

The use of ammoniated or nonammoniated latex extracts for the diagnosis of latex allergy is still a matter of debate. The aim of our study was to compare the characteristics of the two types of extracts by immunoblotting and RAST techniques in children with ascertained latex allergy.

METHODS

Ammoniated (AL) and nonammoniated latex (NAL) extracts were prepared and blotted on SDS-PAGE to resolve their components. Also a solid phase for RAST assays was prepared with the two extracts. The sera from 18 children (mean age 11.4 years, range 6-15 years), with ascertained latex allergy (clinical history, skin test, CAP-RAST and provocation) were used for the experiments.

RESULTS

The NAL extract is resolved in many bands (5-100 kDa), whereas AL showed only few components, likely Hev b 4, 6 and 7. IgE reactivity against AL was observed only in 5/18 patients, whereas 12/18 were positive with NAL. The blotting profile against NAL was complex and the IgE recognition pattern involved different bands.

CONCLUSION

The extract obtained from NAL is able to detect specific IgE against a greater number of allergenic determinants, and therefore a greater diagnostic accuracy can be expected.

[Latex allergy in children]

The aim of our study was to determine the prevalence of latex allergy and the clinical features of children with latex allergy.

PATIENTS AND METHODS

We prospectively investigated 243 children consulting in our allergy out-patients unit during 1 year. Parents answered a questionnaire, and children underwent skin prick tests with common allergens and latex. Latex-specific serum immunoglobulin E was determined by CAP test in children with latex sensitization. The results were compared in children with and without latex allergy.

RESULTS

The prevalence of latex allergy was 1.3%. A family history of atopy (75%) and a personal history of previous surgery was associated with latex allergy (P < 0.0001). In children with latex allergy, the frequency of sensitization to inhaled and food allergens, atopic dermatitis, rhinitis and conjunctivitis was higher than in children without latex allergy (P < 0.05). Avocado allergy was the food allergy most commonly associated with clinical symptoms. Balloon was the most common latex product causing symptoms (60%).

CONCLUSIONS

Due to its potential severe consequences, latex allergy should be investigated in children who had undergone multiple surgical procedures and in the children with pollen-food allergy syndrome. Avoidance of latex is an important preventive measure.

Strategies for distinguishing asymptomatic latex sensitization from true occupational allergy or asthma

OBJECTIVE

To evaluate strategies for distinguishing those individuals with true occupational asthma caused by exposure to natural rubber latex from those individuals with allergic disease related to other allergens.

DATA SOURCES

Article published between January 1, 1981, and December 31, 2001, were identified via a MEDLINE search with the following keywords: latex, allergy, asthma, occupation asthma, and adverse reactions.

STUDY SELECTION

English-language reports concerning diagnostic methods in latex and other forms of occupational asthma.

RESULTS

Many methods have been evaluated for the diagnosis of latex allergy, including medical history, skin prick tests, in vitro tests, and various challenge tests. Skin prick tests with well characterized latex extracts are highly sensitive and specific predictors of latex-specific IgE antibodies; however, direct pulmonary challenge with latex allergen appears to be the only highly reliable method for diagnosis of latex-related occupational asthma.

CONCLUSIONS

It is difficult to optimally distinguish between occupational latex asthma and asymptomatic latex sensitization in a person with preexisting asthma using currently available techniques.

IgE-mediated natural rubber latex allergy: practical considerations for health care workers

OBJECTIVE

To focus on some specific topics of major significance for health care workers confronted with natural rubber latex (NRL) allergy: 1) sensitization and routes of exposure; 2) threshold allergen exposure levels; 3) evaluation of occupational NRL allergy; 4) prevention of sensitization and allergic reactions to NRL-containing devices; 5) selecting the right alternative; and 6) regulatory responses to NRL allergy issues.

DATA SOURCES

English and French language papers identified through a MEDLINE search and bibliographies of the identified papers and the National Institute for Occupational Safety and Health and Food and Drug Administration web sites.

RESULTS

1) The threshold levels of NRL exposure needed for sensitization and the precise way in which it comes about remain to be elucidated, but cutaneous, percutaneous, mucosal, and parenteral exposure can all give rise to symptoms. 2) Strengths and weaknesses of the questionnaire and currently available diagnostic techniques for NRL allergy are emphasized. 3) Prevention strategies should focus on dipped materials and stress upon the possibility of passive and active transmission of NRL aeroallergen. 4) Generally, vinyl gloves are an appropriate alternative for NRL gloves; however, when barrier integrity is a concern, nitrile gloves provide protection that is comparable with NRL. 5) Several government bodies, standards organizations, and regulatory agencies have issued regulations concerning the control and labeling of protein and allergen levels in NRL products.

CONCLUSION

Accurate diagnosis and management of NRL allergy is essential because of the potential for severe hypersensitivity reactions. Major developments have been made in characterizing and cloning NRL allergens, and future development in this area may lead to better diagnostic tools and possible therapeutic agents for immunotherapy. However, at present, avoidance remains the only effective approach. We hope that additional well performed prospective incidence studies will bring more accurate data concerning sensitization doses and provide the valuable information to improve prevention strategies.

Latex hypersensitivity: personal data and review of the literature

Latex allergy is an increasingly common condition, because use of latex products is widespread. The reactions to latex manufactures can be classified as allergic and non-allergic, these are the most common. Latex proteins are responsible for immediate IgE-mediated hypersensitivity allergic reactions. Symptoms range from rhinitis, conjunctivitis and urticaria to anaphylactic shock. Chemical additives can cause allergic contact dermatitis. The clinical symptoms of latex allergy could arise from direct contact with latex products, but may also result from inhalation of airborne allergens. Subpopulations at particular risk include: atopics, children with spina bifida or individuals who required frequent surgical instrumentations, health care workers, and all persons who have regular contact with latex products. Diagnosis of allergy is based initially on history: search for specific serum IgE, skin prick test and provocation test may confirm the suspicion. The most effective strategy in the treatment of latex allergy is avoidance, however this is virtually impossible, given large number of latex products we encounter since childhood. In this paper we review the current state of knowledge concerning latex allergy, including the clinical spectrum, identified allergens, the cross-reactions regarding the latex-fruit syndrome, diagnostic procedures and preventive measures. Several personal data increase awareness on this issue.