Update on the evaluation of hypersensitivity reactions to betalactams

Educational case series: β-lactam allergy and cross-reactivity

Penicillins and cephalosporins are the most widely used antibiotics for the treatment of common infections, and they are the two main classes of β-lactams. On the basis of the time of appearance of the reaction after drug intake and for diagnostic purposes, hypersensitivity reactions to β-lactams have been classified as immediate or non-immediate. The diagnostic evaluation of allergic reactions to β-lactams has changed over the last decade, for several reasons. In many countries, major and minor determinants for skin testing are not available. In immediate allergic reactions, the sensitivity of skin testing is decreasing. For non-immediate reactions, skin testing appears to be less sensitive than previously reported. The drug provocation test is still necessary for diagnosis. In this education review series, we described three cases of β-lactam allergy: first, a child with an IgE-mediated allergy to benzyl-penicillin; second, a child with a non-allergic hypersensitivity to amoxicillin; and in the third patient, we will discuss about cross-reactivity between penicillins and cephalosporins. These cases are correlated with the practical management of evaluating β-lactam allergy.

Short protocol for the study of paediatric patients with suspected betalactam antibiotic hypersensitivity and low risk criteria

BACKGROUND

Suspected hypersensitivity to betalactam antibiotics in children is a frequent cause of consultation that proves costly in terms of resource utilization--particularly time. Such hypersensitivity is, however, rarely confirmed.

METHODS

A short protocol was introduced in which patients at low risk (single episode with mild, non-immediate skin symptoms after the administration of a betalactam antibiotic via the oral route) were subjected to oral provocation (following the obtaining of informed consent) without any other prior evaluations. Patients failing to meet these requirements were studied according to the protocol of the EAACI (specific IgE and skin testing prior to oral provocation).

RESULTS

A total of 78 patients (56 at low risk) were studied. Five patients had tolerated the medication after the episode, while another six patients failed to complete the study. The study with oral provocation was completed in the remaining 67 patients: according to the protocol of the EAACI in 17 patients, and using the short protocol in 50 patients. Only one patient showed a positive provocation test, of a delayed and mild nature.

CONCLUSIONS

Direct oral provocation in low risk patients has been shown to be effective and safe in discarding hypersensitivity to betalactam antibiotics in the majority of the patients studied.

Drug provocation tests in hypersensitivity drug reactions

PURPOSE OF REVIEW

Drug provocation test (DPT) is necessary to diagnose most drug hypersensitivity reactions (HSRs) due to decreased sensitivity of skin testing even when combined with in-vitro tests in immunonologic drug HSR and limited availability of these tests in nonimmunologic reaction. We review the principles and controversial issues of DPT, and recent studies using DPT as a diagnostic tool.

RECENT FINDINGS

DPT is recommended in the diagnosis of HSR to β-lactams, as well as other drug classes [such as acetylsalicylic acid-NSAIDs (ASA-NSAIDs), non-β-lactams antibiotics, heparin, glucocorticoids, and local anesthetic agents]. In view of the decreased sensitivity of skin testing, limited accessibility to new benzylpenicillin polylysine (PPL)/mixture of minor determinant (MDM) test reagents and limited availability of validated sensitive in-vitro tests, individuals who require DPT to β-lactams are increasing. The negative predictive value of allergologic work-up is very high, ranging from 94 to 98% for β-lactams and those reactions after negative tests are mostly nonimmediate and mild. Finally, DPT is recommended to ascertain tolerability of alternative compound when evaluating cross-reactivity among different classes of β-lactams, NSAIDs and glucocorticoids, and possibly iodinated contrast media.

SUMMARY

DPT is often needed when evaluating patients with suspected drug HSR. More studies regarding standardization of the various protocols are needed in order to increase its acceptance and adoption as a standard practice in the diagnostic algorithm for drug HSR.

The in vitro diagnosis of drug allergy: status and perspectives

Adverse drug reactions (ADR) can result from immune-mediated (drug allergy) and nonimmune-mediated mechanisms. In both types of reaction, conclusive diagnosis and appropriate management remain major problems in daily clinical practice. This review summarizes the potentials and shortcomings of the currently available in vitro tests in the diagnosis of immediate (mostly IgE mediated) and nonimmediate (mostly T-cell mediated) drug allergy, particularly quantification of specific IgE, flow-assisted analysis of in vitro activated lymphocytes and basophils and the enzyme-linked immunosorbent spot.

A statement on cefazolin immediate hypersensitivity: data from a large database, and focus on the cross-reactivities

BACKGROUND

More perioperative cefazolin use has resulted in an increased risk of cefazolin-associated reactions.

OBJECTIVE

The aim of this article is to study immediate reactions to cefazolin and attempt to determine possible allergic cross-reactivity with other ß-lactams using data from the Drug Allergy and Hypersensitivity Database (DAHD).

METHODS

All 25 cefazolin-associated reactions in the DAHD were reviewed. The cases identified were then investigated according to the European Network for Drug Allergy (ENDA) recommendations by skin testing and challenges.

RESULTS

A total of 10 individuals with proven IgE-mediated cefazolin hypersensitivity were identified between January 1999 and July 2009. All the index reactions were compatible with an acute IgE-mediated process, six with anaphylaxis, two with systemic allergic reactions without hypotension, and two with urticaria/angioedema. Cefazolin skin tests were positive in seven individuals and cefazolin challenges were positive in three more individuals. In the eight cefazolin allergic patients who had challenges with other ß-lactams, there was no positive reaction noted.

CONCLUSION AND CLINICAL RELEVANCE

In this cohort of patients with IgE-mediated reactions to cefazolin, a majority tolerated amoxicillin and several patients tolerated other cephalosporins. This implies that the R1 side-chain may play an essential role in IgE-mediated reactions to cefazolin. No clear rule to predict cross-reactivity with other ß-lactams could be determined. More research on IgE-mediated hypersensitivity to cefazolin and other cephalosporins is needed.

Educational case series: Mechanisms of drug allergy

Once administered, a drug can activate the immune system by various mechanisms and lead to a large range of clinical manifestations closely related to the type of immune reaction elicited. Administration of the drug can classically result in an immunoglobulin E (IgE)-type sensitization, but can also result in more complex activation of the immune system potentially resulting in severe syndromes, such as the drug-induced hypersensitivity syndrome (DIHS). Although there has been a major increase in our knowledge over the last years, the exact mechanisms of drug allergy are not well understood for most clinical manifestations. A complex interaction between individual characteristics, environmental factors, and the drug itself is usually responsible for adverse reactions to drugs. In this educational review series, we described three cases of drug allergy: first, a child with a typical IgE-mediated drug allergy, second, a child with a non-immediate reaction to penicillin, and in the third patient, we will discuss the drug-induced hypersensitivity syndrome, which is rare but potentially fatal. These cases are correlated to the immune mechanism potentially involved.

Methodologies to anchor dendrimeric nanoconjugates to solid phase: toward an efficient in vitro detection of allergy to β-lactam antibiotics

β-lactam antibiotics are the most common cause of adverse drug reactions, and in vitro immunoassays are often employed to diagnose this allergy. Cellulose solid supports displaying hapten-carrier conjugates are traditionally used for quantifying specific IgE antibodies to determine whether a patient is allergic to the hapten. Our approach makes use of polyamidoamine dendrimers as carriers, and differs from traditional solid-phase activation methods by using two different haloalkanoyl halides as reagents instead of cyanogen bromide. Evaluation of the functionalization in the three different surfaces with benzylpenicilloyl-dendrimer conjugates showed a higher density of conjugates when using haloalkanoyl halides. The resulting surfaces were evaluated in vitro by radioimmunoassay using sera from patients allergic to penicillins. Selective and specific IgE recognition was observed in the different activated disks, though those activated with haloalkanoyl halides presented better sensitivity.

FROM THE CLINICAL EDITOR

A novel and sensitive method of dendrimeric nanoconjugate-based in vitro detection of allergy to β-lactam antibiotics is presented in this basic science paper.

Antibiotic Allergy

Antibiotics are commonly injected during the perioperative period and are responsible of 15% of the anaphylactic reactions. Anaphylaxis triggered by antibiotics primarily involves penicillin and cephalosporin. The management of patients with histories of allergic reactions to antibiotics is a common situation in clinical practice. The confirmation or invalidation of the allergic nature of the reported reaction is not based on in vitro tests, but on a rigorous allergological work-up based on detailed analysis of clinical history, skin tests and drug provocation test. Considering a possible cross-reactivity between penicillins, once an immediate penicillin allergy has been diagnosed, skin testing with the alternative molecule (cephalosporin, carbapenem, aztreonam) is mandatory and, if negative, the relevant drug should be given in an appropriate setting at increasing doses.

Peri-operative anaphylaxis

Peri-operative anaphylaxis is an important cause for mortality and morbidity associated with anaesthesia. The true incidence is unknown and is most likely under reported. Diagnosis can be difficult, particularly as a number of drugs are given simultaneously and any of these agents can potentially cause anaphylaxis. This review covers the clinical features, differential diagnosis and management of anaphylaxis associated with anaesthesia. The investigations to confirm the clinical suspicion of anaphylaxis and further tests to identify the likely drug(s) are examined. Finally the salient features of common and rare causes including non-drug substances are described.

Diagnosis and management of drug hypersensitivity reactions

The present article addresses the advances in the diagnosis and management of drug hypersensitivity reactions that were discussed in the 4th Drug Hypersensitivity Meeting held in Rome in April 2010. Such reactions can be classified as immediate or nonimmediate according to the time interval between the last drug administration and onset. Immediate reactions occur within 1 hour, and nonimmediate reactions occur after more than 1 hour. Clinical and immunologic studies suggest that type-I (IgE-mediated) and type-IV (T cell-mediated) pathogenic mechanisms are involved in most immediate and nonimmediate reactions, respectively. In diagnosis prick, patch, and intradermal tests are the most readily available tools. Determination of specific IgE levels is still the most common in vitro method for diagnosing immediate reactions. New diagnostic tools, such as the basophil activation test, the lymphocyte activation test, and enzyme-linked immunospot assays for analysis of the frequency of antigen-specific, cytokine-producing cells, have been developed for evaluating either immediate or nonimmediate reactions. The sensitivity of allergologic tests is not 100%; therefore in selected cases provocation tests are necessary. In the diagnosis of nonallergic hypersensitivity reactions to nonsteroidal anti-inflammatory drugs, the provocation test with the suspected drug still represents the "gold standard." However, there was no consensus regarding the use of this test in subjects with histories of hypersensitivity reactions to 1 (single reactors) or more (multiple reactors) nonsteroidal anti-inflammatory drugs. With regard to management, desensitization allows patients to be treated with irreplaceable chemotherapy agents, such as taxanes, platinum salts, and mAbs, to which they have presented hypersensitivity reactions. Desensitization also permits the use of aspirin in aspirin-sensitive patients undergoing revascularization and in subjects with aspirin-exacerbated respiratory disease.

Challenge Test Results in Patients With Suspected Penicillin Allergy, but No Specific IgE

Purpose

Patients with a history of allergic reaction to penicillin, but with no detectable specific IgE, are common and pose a dilemma. Challenge tests are considered to be the diagnostic gold standard. The aim of this study was to identify subgroups of patients with very low risk for reactions who could be safely tested using a more rapid and simple procedure.

Methods

A total of 580 consecutively referred adult patients with a history of non-serious cutaneous allergic reactions to penicillin, but with no IgE, were challenged with therapeutic doses of penicillin V (phenoxymethylpenicillin), penicillin G (benzylpenicillin), or both.

Results

Only 14 of 580 patients had a positive challenge test. In 11 of the 14, a reaction to challenge occurred within 2 hours, and none were anaphylactic. The year of the original reaction was known for 555 patients; a positive challenge was seen in only 0.4% of those with an original reaction >15 years before challenge, but in 4.6% of those with a more recent original reaction (P=0.001). Onset of a reaction within the first day of the original exposure was a predictive factor for a positive challenge (P=0.001) in patients challenged within 15 years of the original reaction.

Conclusions

Among suspected penicillin-allergic patients with non-severe skin reactions and no detectable specific IgE, the subgroup of patients who originally reacted more than 15 years previously had very low risk for reacting to a challenge. The risk was higher in patients with a more recent original reaction, especially if the symptoms had occurred within the first day of exposure.

Full-course drug challenge test in the diagnosis of delayed allergic reactions to penicillin

BACKGROUND

Drug challenge test (DCT) has long been the most sensitive test in the allergological work-up when investigating for penicillin allergy.

OBJECTIVE

To improve sensitivity of the diagnostic work-up in diagnosing penicillin allergics with histories of allergic reactions on day 2 or later in the course of penicillin treatment.

METHODS

A full-course DCT was added to the current protocol if specific IgE, skin tests and DCT were all negative in patients who had a nonimmediate reaction to penicillin treatment. Sixteen patients with a history of an immediate reaction to penicillin treatment underwent testing with negative outcomes.

RESULTS

Fifty percent of patients undergoing full-course DCT experienced a cutaneous adverse drug reaction. None of the controls reacted (p = 0.001). The mean time of reaction was 6 days. Penicillin V accounted for most reactions. Urticaria was the most frequent clinical reaction observed.

CONCLUSIONS

Full-course DCT offers an improvement of sensitivity and predictive values of the diagnostic work-up of allergic reactions to penicillin occurring on day 2 of penicillin treatment or later.

Childhood acute urticaria in northern and southern Europe shows a similar epidemiological pattern and significant meteorological influences

Acute urticaria (AU) is a common condition that often presents in childhood. Although there is a general perception of cyclic annual trends in AU, no one has tried to identify any seasonal variation on its prevalence and incidence, associate environmental influences and impute geographic, ethnic, or even genetic features that may contribute to its onset. We aimed to analyze the influence of climate and geographic parameters on annual fluctuation of AU cases referred to the Emergency Departments (EDs) of Norwich (UK) and Heraklion (Crete, Greece), compare all identifiable potential triggers and severity, and calculate the prevalence and incidence of AU. Record-based data of all children up to 14 yr of age referred to both EDs between June 2005 and May 2007 were examined retrospectively. Demographic characteristics and any potential identifiable triggers of AU were recorded and compared. Poisson's regression was utilized to examine any influence of meteorological parameters on AU incidence. Edwards' test for seasonality was applied to identify any significant seasonal trend of the AU incidence within each city. Seven hundred and twenty-nine AU cases were identified (324 in Norwich and 405 in Heraklion), among 56,624 total referrals (28,931 and 27,693 cases, respectively). Respiratory infections were found to be the most commonly associated potential triggers of AU and food allergens the least. AU cases and incidence rates in both cities were equally distributed during the study period. A non-significant seasonal trend in AU incidence (October, April-May) was observed in Norwich, in contrast to a significant seasonal pattern (December, February-May) of AU in Heraklion. Temperature was inversely associated with AU incidence, while the statistically significant effect of relative humidity varied. Acute childhood urticaria shows a similar epidemiological pattern in northern and southern Europe regardless of the expected differences in genetic, geographic, and environmental background. Temperature and humidity are correlated with AU incidence. Seasonality of several acute respiratory viral infections, the most prominent associated trigger of AU, coincides with the observed AU seasonality, suggesting a potential linkage. However, this needs to be elucidated from larger epidemiological studies.

Practical management of antibiotic allergy in adults

This review looks at the main issues around immediate hypersensitivity and the role and limitations of testing. The majority of literature on antibiotic hypersensitivity relates to β-lactam antibiotics, mainly because of the heavy usage of this class of drugs. Concerns around cross-reactivity always worry clinicians, particularly in the emergency situation. Reasonable data now exist in relation to β-lactam antibiotics and derivatives, which enable appropriate risk management to be undertaken. The available literature for other classes of antibiotics is also discussed.

IgE-mediated hypersensitivity to cephalosporins: cross-reactivity and tolerability of penicillins, monobactams, and carbapenems

BACKGROUND

There have been few studies regarding the cross-reactivity and tolerability of penicillins, aztreonam, and carbapenems in large samples of subjects with cephalosporin allergy.

OBJECTIVE

We sought to evaluate the possibility of using penicillins, monobactams, and carbapenems in subjects with cephalosporin allergy who especially require them.

METHODS

We conducted a prospective study of 98 consecutive subjects who had 106 immediate reactions (mostly anaphylactic shock) to cephalosporins and had positive skin test results for these drugs. To assess the cross-reactivity with penicillins, monobactams, and carbapenems and the tolerability of such alternative β-lactams, all subjects underwent skin tests and serum-specific IgE assays with penicillin reagents, as well as skin tests with aztreonam, imipenem/cilastatin, and meropenem. Subjects with negative test results were challenged with meropenem, imipenem/cilastatin, aztreonam, and amoxicillin.

RESULTS

Positive allergologic test results to penicillins were displayed by 25 (25.5%) subjects, including 1 with positive results to all reagents tested and another with a positive result to aztreonam. Another subject had positive results to both ceftazidime and aztreonam. A reaction to cephalosporins with side-chain structures similar or identical to those of penicillins was a significant predictor of cross-reactivity because of an increased 3-fold risk of positive results on allergologic tests with penicillin determinants. Challenges with alternative β-lactams were tolerated, with the exception of 1 urticarial reaction to imipenem/cilastatin.

CONCLUSIONS

About 25% of subjects with cephalosporin allergy had positive results to penicillins, 3.1% to aztreonam, 2% to imipenem/cilastatin, and 1% to meropenem. In those who especially require alternative β-lactams, pretreatment skin tests are advisable because negative results indicate tolerability of the β-lactam concerned.

Drug provocation tests to betalactam antibiotics: experience in a paediatric setting

BACKGROUND

Few studies have been performed in children with suspected betalactam allergy. We aimed to assess the role of the drug provocation test (DPT) with betalactams in a paediatric setting and to study the association between allergy to betalactam antibiotics and other allergic diseases.

METHODS

We included all the patients under 15 years old who were consecutively referred to the Immunoallergy Department, Dona Estefânia Hospital, Portugal (January 2002 to April 2008) for a compatible history of allergic reaction to betalactam. All were submitted to a DPT. Children were proposed to perform skin tests (ST) to betalactam antibiotics followed by DPT. If they decline ST, a DPT with the culprit drug was performed.

RESULTS

We studied 161 children, 60% were boys, with a median age of 5 years old at the time of the DPT. Thirty-three patients (20.5%) had an immediate reaction and 33 (20.5%) a non-immediate reaction. The severity of the reported reactions was low in most cases. Skin tests to betalactams were performed in 47 children and were positive in 8. DPT was positive in only one (3.4%) of the patients skin tested and in 11 (13.4%) of those not skin tested. The severity of the DPT reaction was low. Asthma and food allergy were associated with a positive DPT in the later group.

CONCLUSIONS

DPT seems a safe procedure even in the absence of ST in non-severe cases. This could be a practical option in infants and pre-school children, where ST are painful and difficult to perform. Additional caution should be taken in children with asthma and food allergy.

The very limited usefulness of skin testing with penicilloyl-polylysine and the minor determinant mixture in evaluating nonimmediate reactions to penicillins

BACKGROUND

The contribution of skin testing with penicilloyl-polylysine (PPL) and the minor determinant mixture (MDM) to the diagnosis of hypersensitivity reactions to penicillins differs greatly according to the type of reaction: immediate (occurring within 1 h after the last drug administration) or nonimmediate (occurring more than 1 h after the last drug administration).

OBJECTIVE

To assess the contribution of skin testing with PPL and MDM to the diagnosis of nonimmediate reactions to penicillins.

METHODS

We evaluated 162 adults who had had 232 nonimmediate reactions to penicillins, mostly aminopenicillins, and presented positive skin and/or patch tests to one or more penicillin reagents: PPL, MDM, benzylpenicillin, ampicillin, and amoxicillin, as well as any responsible penicillins.

RESULTS

A total of 157 subjects (96.9%) displayed patch-test and/or delayed-reading intradermal-test positivity to penicillin reagents, which indicates a cell-mediated hypersensitivity; six of them also presented immediate-reading skin-test positivities. All 157 patients with a cell-mediated hypersensitivity were positive to the responsible penicillins (parent drugs); 16 of them also displayed delayed-reading intradermal-test positivity to MDM. Five (3.1%) of the 162 patients displayed only immediate-reading skin-test positivity (four to PPL and one to amoxicillin). Overall, 158 subjects (97.5%) presented positive responses to the responsible penicillins, while only 9 (5.5%) and 17 (10.5%) were positive to PPL and MDM, respectively.

CONCLUSIONS

The contribution of skin testing with PPL and MDM in diagnosing nonimmediate hypersensitivity reactions to penicillins, especially cell-mediated ones, is very limited. This finding could be useful at a time when PPL and MDM are not available in all countries.

Autism spectrum disorders and allergy: observation from a pediatric allergy/immunology clinic

IgE-mediated allergic diseases (e.g., allergic rhinoconjunctivitis, atopic asthma and food allergy) are prevalent (up to 30%) in the general population and are increasing in developed countries. In infants and young children, non-IgE-mediated food allergy is also prevalent. In addition to easily recognized organ-specific symptoms, allergic diseases can cause neuropsychiatric symptoms, such as irritability and hyperactivity, in otherwise healthy individuals. This is also likely to occur in children with autism spectrum disorder (ASD). Moreover, the discomfort and pain associated with allergic diseases could aggravate behavioral symptoms in ASD children. Allergic conditions are easily treatable; however, ASD children may be underdiagnosed and/or undertreated for allergic and other common childhood diseases, in part due to their impaired communication skills. Practicing physicians should be aware of the potential impact of allergic diseases on behavioral symptoms and cognitive activity in ASD children. However, they also need to be aware that certain symptoms often attributed to 'allergy' by caregivers may not be immune mediated and should understand that behavioral symptoms can also be affected by many non-IgE-mediated causes.

Penicillin skin testing in the evaluation and management of penicillin allergy

OBJECTIVE

to review the role of penicillin skin testing in the evaluation and management of penicillin allergy mediated by IgE.

DATA SOURCES

PubMed and OVID search of English-language articles regarding penicillin allergy, penicillin allergy testing, and management of penicillin allergy.

STUDY SELECTION

articles pertinent to the subject matter were selected and reviewed.

RESULTS

the major determinant (benzylpenicillin polylysine) detects the greatest number of penicillin allergic patients during skin testing, and the minor determinants of penicillin increase the sensitivity of penicillin skin testing. Penicillin skin testing to the major and minor determinants was found to have a negative predictive value of 97% to 99%. The incidence of systemic adverse reaction to penicillin skin testing is less than 1%.

CONCLUSION

a detailed history of the prior reaction to penicillin is an integral part of the evaluation, but it is not accurate in predicting a positive penicillin skin test result. A patient with a negative penicillin skin test result to the major and minor determinants is at a low risk of an immediate-type hypersensitivity reaction to penicillin. Patients with a positive skin test result should undergo desensitization to penicillin or an alternative antibiotic should be considered.

Perioperative anaphylaxis

The incidence of immune-mediated anaphylaxis during anesthesia ranges from 1 in 10,000 to 1 in 20,000. Neuromuscular blocking agents are most frequently incriminated, followed by latex and antibiotics, although any drug or substance used may be a culprit. Diagnosis relies on tryptase measurements at the time of the reaction and skin tests, specific immunoglobulin E, or basophil activation assays. Treatment consists of rapid volume expansion and epinephrine administration titrated to symptom severity.

The complex clinical picture of beta-lactam hypersensitivity: penicillins, cephalosporins, monobactams, carbapenems, and clavams

Beta-lactam antibiotics are the drugs most frequently involved in drug hypersensitivity reactions that are mediated by specific immunologic mechanisms. In addition to benzylpenicillin, several chemical structures belonging to 5 major subgroups can induce reactions. The most relevant structure is that of the amoxicillin molecule. Reactions belong to the 4 major mechanisms described by Coombs and Gell, whereby type IV reactions have recently been further subclassified. The most frequent reactions are type I, which are IgE mediated, and type IV, which are nonimmediate and T-cell dependent. IgE-specific antibodies may recognize the benzylpenicilloyl structure or another part of the molecule, such as the side chain, as antigenic determinants. Depending on specific recognition, subjects can be either cross-reactors or selective responders. A variety of entities exist in T-cell reactions, ranging from mild exanthema to life-threatening, severe reactions, such as Stevens-Johnson syndrome or toxic epidermal necrolysis. Diagnostic tests for IgE-mediated reactions can be done in vivo by testing skin with different penicillin determinants or in vitro by quantitating specific IgE antibodies. For nonimmediate reactions, there are also in vitro and in vivo tests, with variable degrees of sensitivity and specificity. The natural history of IgE-mediated reactions indicates that the count of specific IgE antibodies decreases over time and that results of diagnostic tests can become negative.

Role of minor determinants of amoxicillin in the diagnosis of immediate allergic reactions to amoxicillin

BACKGROUND

Skin testing of subjects with immediate hypersensitivity to amoxicillin is performed using major and minor determinants of benzylpenicillin plus amoxicillin. However, sensitivity is not optimal, and other determinants need to be considered. We assessed the sensitivity of stable, well-characterized minor determinants of amoxicillin in subjects with immediate allergic reactions to amoxicillin to improve skin test sensitivity.

METHODS

Amoxicillin, amoxicilloic acid, and diketopiperazine were prepared and characterized by reverse-phase HPLC, tested in vivo by skin testing and in vitro by basophil activation test and RAST inhibition assay.

RESULTS

Patients with immediate hypersensitivity to amoxicillin were selected: Group A (n = 32), skin test positive just to amoxicillin; Group B (n = 19), skin test positive to benzylpenicillin determinants; Group C (n = 10), skin test negative and amoxicillin drug provocation test positive. In Group A, 27 subjects (81.8%) were skin test positive to amoxicillin, ten (30.3%) to amoxicilloic acid, two (6.1%) to diketopiperacine, and six (18.2%) negative. In Group B, nine (50%) were positive to amoxicillin, eight (42.1%) to amoxicilloic acid, none to diketopiperacine, and nine (50%) negative. In Group C, skin tests were negative. BAT was positive to amoxicillin in 26 patients (50.9%), to amoxicilloic acid in 15 (29.1%), and diketopiperazine in four (7.8%). RAST inhibition studies showed > 50% inhibition in all sera, with the highest concentration of amoxicillin and amoxicilloic acid.

CONCLUSIONS

The combination of minor determinants of amoxicillin, amoxicilloic acid, and diketopiperazine seems to be of no greater value than the use of amoxicillin alone. Further efforts are needed to find new structures to improve sensitivity in the diagnosis of immediate hypersensitivity to betalactams.

Determining the negative predictive value of provocation tests with beta-lactams

BACKGROUND

The beta-lactam allergic work-up is mostly standardized. However, the negative predictive value of drug provocation tests is not yet well established.

METHOD

A historical-prospective multicentre cohort study was conducted in four centres (one in France, one in Portugal, two in Italy) to assess the negative predictive value of provocation tests with beta-lactams in patients initially tested for a suspicion of drug allergy/hypersensitivity. Patients were contacted at least 6 months after the work-up, between 2003 and 2007. A new allergic work-up was proposed to reacting patients.

RESULTS

Among the 457 patients included, 365 (79.9%) were followed up (159 [79.1%] from France, 153 [82.7%] from Italy and 53 [74.6%] from Portugal). Only 118 (25.8%) were re-exposed to the negatively tested beta-lactam. Nine (7.6%) reported a non-immediate (occurring more than 1 h after drug administration) reaction: five urticaria, three exanthema and one undefined cutaneous reaction. None were severe. Only four accepted a re-challenge, negative in two cases and positive in the two others. The negative predictive value was 94.1% (89.8-98.3) (111 out of 118 patients).

CONCLUSION

Although the negative predictive value of drug provocation tests may not be 100%, none of the false negative patients experienced a life-threatening reaction. This should reassure doctors who might hesitate to prescribe beta-lactams, even in patients with negative allergic work-ups.

In vitro detection and characterization of drug hypersensitivity using flow cytometry

BACKGROUND

The lymphocyte transformation test (LTT) is the only in vitro test for detecting drug sensitization at the cellular level irrespective of the reaction's phenotype. However, the LTT includes working with radioactive substances and is considered impracticable for routine laboratory investigation.

OBJECTIVE

The aim of this study was to assess drug-specific cytokine production by means of flow cytometry as an alternative nonradioactive approach which may be more appropriate for routine testing and may provide in addition more information about the pathophysiology of the reaction than proliferation-based assays, like the LTT.

METHOD

Peripheral blood mononuclear cells of 19 patients were incubated with culprit drugs (n = 28) or irrelevant antigens (n = 10). Ten healthy persons served as controls for all different drugs (n = 15). Intracellular interleukin (IL)-5, interferon (IFN)-gamma and IL-10 production was investigated using flow cytometry. Accuracy of the flow cytometry test system was confirmed using different statistical tests, i.e. receiver operating characteristic curve and Mann-Whitney rank test. In addition, drug-specific secretion of IL-5, IL-2 and IFN-gamma were analysed using enzyme-linked immunosorbent assay (ELISA).

RESULTS

Drug-specific cytokine production could be demonstrated in 75% of the patients using flow cytometry and in 79% using ELISA respectively. Combining ELISA and flow cytometry increased the sensitivity to 100%. Analysis of involved T-cell subsets [e.g. CD4(+) or CD8(+); T helper (TH) 1 or TH 2] allowed characterization of the in vitro lymphocyte reactivity pattern.

CONCLUSIONS

Analysis of drug-specific cytokine production by means of flow cytometry proved a useful and reliable approach for the in vitro detection and characterization of drug hypersensitivities.