Interpretation of subjective symptoms in double-blind placebo-controlled food challenges - interobserver reliability

Physician's appraisal vs documented signs and symptoms in the interpretation of food challenge tests: The EuroPrevall birth cohort

BACKGROUND

Blinded food challenges are considered the current gold standard for the diagnosis of food allergies. We used data from a pan-European multicenter project to assess differences between study centers, aiming to identify the impact of subjective aspects for the interpretation of oral food challenges.

METHODS

Nine study centers of the EuroPrevall birth cohort study about food allergy recruited 12 049 newborns and followed them for up to 30 months in regular intervals. Intensive training was conducted and every center visited to ensure similar handling of the protocols. Suspected food allergy was clinically evaluated by double-blind, placebo-controlled food challenges using a nine dose escalation protocol. The primary challenge outcomes based on physician's appraisal were compared to documented signs and symptoms.

RESULTS

Of 839 challenges conducted, study centers confirmed food allergy in 15.6% to 53.6% of locally conducted challenges. Centers reported 0 to 16 positive placebo challenges. Worsening of eczema was the most common sign when challenged with placebo. Agreement between documented objective signs and the challenge outcome assigned by the physician was heterogeneous, with Cohen's kappa spanning from 0.42 to 0.84.

CONCLUSIONS

These differences suggest that the comparison of food challenge outcomes between centers is difficult despite common protocols and training. We recommend detailed symptom assessment and documentation as well as objective sign-based challenge outcome algorithms to assure accuracy and comparability of blinded food challenges. Training and supervision of staff conducting food challenges is a mandatory component of reliable outcome data.

A new framework for the documentation and interpretation of oral food challenges in population-based and clinical research

BACKGROUND

The conduct of oral food challenges as the preferred diagnostic standard for food allergy (FA) was harmonized over the last years. However, documentation and interpretation of challenge results, particularly in research settings, are not sufficiently standardized to allow valid comparisons between studies. Our aim was to develop a diagnostic toolbox to capture and report clinical observations in double-blind placebo-controlled food challenges (DBPCFC).

METHODS

A group of experienced allergists, paediatricians, dieticians, epidemiologists and data managers developed generic case report forms and standard operating procedures for DBPCFCs and piloted them in three clinical centres. The follow-up of the EuroPrevall/iFAAM birth cohort and other iFAAM work packages applied these methods.

RECOMMENDATIONS

A set of newly developed questionnaire or interview items capture the history of FA. Together with sensitization status, this forms the basis for the decision to perform a DBPCFC, following a standardized decision algorithm. A generic form including details about severity and timing captures signs and symptoms observed during or after the procedures. In contrast to the commonly used dichotomous outcome FA vs no FA, the allergy status is interpreted in multiple categories to reflect the complexity of clinical decision-making.

CONCLUSION

The proposed toolbox sets a standard for improved documentation and harmonized interpretation of DBPCFCs. By a detailed documentation and common terminology for communicating outcomes, these tools hope to reduce the influence of subjective judgment of supervising physicians. All forms are publicly available for further evolution and free use in clinical and research settings.

Standardization of double blind placebo controlled food challenge with soy within a multicentre trial

Background

Multicentre trials investigating food allergies by double blind placebo controlled food challenges (DBPCFC) need standardized procedures, challenge meals and evaluation criteria. We aimed at developing a standardized approach for identifying patients with birch related soy allergy by means of DBPCFC to soy, including determination of threshold levels, in a multicentre setting.

Methods

Microbiologically stable soy challenge meals were composed of protein isolate with consistent Gly m 4 levels. Patients sensitized to main birch allergen Bet v 1 and concomitant sensitization to its soy homologue Gly m 4 underwent DBPCFC. Outcome was defined according to presence and/or absence of ten objective signs and intensity of eight subjective symptoms as measured by visual analogue scale (VAS).

Results

138 adult subjects (63.8% female, mean age 38 years) underwent DBPCFC. Challenge meals and defined evaluation criteria showed good applicability in all centres involved. 45.7% presented with objective signs and 65.2% with subjective symptoms at soy challenge. Placebo challenge meals elicited non-cardiovascular objective signs in 11.6%. In 82 (59.4%) subjects DBPCFC was judged as positive. 70.7% of DPBCFC+ showed objective signs and 85.4% subjective symptoms at soy challenge. Subjective symptoms to soy challenge meal in DBPCFC+ subjects started at significantly lower dose levels than objective signs (p < 0.001). Median cumulative eliciting doses for first objective signs in DBPCFC+ subjects were 4.7 g [0.7–24.7] and 0.7 g [0.2–4.7] total soy protein for first subjective symptoms (p = 0.01).

Conclusions

We present the hitherto largest group of adults with Bet v 1 and Gly m 4 sensitization being investigated by DBPCFC. In this type of food allergy evaluation of DBPCFC outcome should not only include monitoring of objective signs but also scoring of subjective symptoms. Our data may contribute to standardize DBPCFC in pollen-related food allergy in multicentre settings.

Trial registration

EudraCT: 2009-011737-27.

Differences between observers in interpreting double-blind placebo-controlled food challenges: a randomized trial

BACKGROUND

Interpretation of double-blind placebo-controlled food challenges (DBPCFC) can be difficult, particularly with ambiguous subjective symptoms. Early opening of the challenge key (which day is verum and which placebo) may influence the clinician's interpretation of the DBPCFC result.

METHODS

Fifty-one clinicians reviewing results of 19 DBPCFCs with ambiguous clinical symptoms were randomized into a key first strategy (opening the DBPCFC key before reviewing the symptoms on both challenge days and deciding on the DBPCFC result) or a symptoms first strategy (reviewing symptoms and interpreting both test days as positive or negative before opening the key and deciding on the DBPCFC result).

RESULTS

The proportion of DBPCFCs considered inconclusive was comparable between the two strategy groups (p = 0.791). Participants in the symptoms first group were more likely to consider a DBPCFC as positive (in 14 tests, 73.7%) than subjects in the key first group (four tests, 21.1%). The number of positive tests was higher in the symptoms first group (median 50.0%, interquartile range [IQR] 23.1-76.9%) than in the key first groups (44.0%, IQR 12.0-68.0%, p = 0.031). This was independent of the participant's profession (pediatrician or other), age, gender, or years of experience (p > 0.3).

CONCLUSIONS

Clinicians differ in their interpretation of DBPCFC results when symptoms are ambiguous. Opening the key of a DBPCFC before reviewing and interpreting symptoms significantly reduces the likelihood of the challenge being interpreted as positive. Guidelines for performing DBPCFCs should standardize the moment of opening the challenge key.

Cow's milk-associated gastrointestinal symptoms evaluated using the double-blind, placebo-controlled food challenge

OBJECTIVE

The aim of this study was to evaluate the suspicion of cow's-milk allergy in infants with unspecific gastrointestinal (GI) symptoms using the double-blind, placebo-controlled food challenge.

METHODS

A prospective cohort study, which recruited 57 consecutive children with gastrointestinally manifested symptoms suspected of cow's-milk allergy. All patients underwent a 5-day double-blind, placebo-controlled food challenge for cow's milk.

RESULTS

The median age of the patients was 8.7 months. None had measurable cow's-milk-specific IgE. The food challenge was positive in 18 (32%) cases, with symptoms manifesting within 48 hours in 17 of 18 cases. The only symptom that correlated with the positive challenge was loose stools, reported as a presenting symptom in 78% of challenge-positive and in 46% of challenge-negative children (P = 0.043). During active challenge, the respective proportions were 82% and 2% (P < 0.0001). No serious adverse effects were manifested during the challenges. In the challenge-negative group, significant placebo reactions occurred in 18 (46%) patients. In the challenge-negative children, adult-type hypolactasia genotype CC frequency was higher (31%, P = 0.033) than national prevalence of 18%.

CONCLUSIONS

In an infant with unspecific GI symptoms suspected of cow's-milk allergy, this diagnosis is seldom confirmed. Other reasons for the troublesome GI symptoms should also be identified.

Outcome of oral food challenges in children in relation to symptom-eliciting allergen dose and allergen-specific IgE

BACKGROUND

Oral food challenge (FC) protocols are discussed with reference to starting doses, dose increments, safety, and predictability of results. The aim of this study was to evaluate the relation of eliciting allergen doses, specific IgE levels and predictive factors to the outcome of FCs in children.

METHODS

In 869 children (median age 1.2 years), FCs were performed with cow's milk (n = 633), hen's egg (n = 456), wheat (n = 265) and/or soy (n = 317) starting at 3-5 mg of protein. Each of the seven doses was administered every 30 min using semi-log increases. Severity of symptoms was graded from I to V. IgE was determined prior to challenges.

RESULTS

Of the children allergic to egg or milk, 9% and 10%, respectively, experienced reactions already at the first dose. Of these, 14% (egg) and 4% (milk) experienced grade IV reactions. In contrast, few children reacted to the first doses of wheat or soy, and most reactions occurred after the maximum dose. For all allergens, grade V reactions did not occur. However, grade IV reactions were seen at all eliciting doses. Elevated specific IgE level, young age and a history of atopic dermatitis were associated with a positive challenge outcome for milk or egg, and also IgE levels were associated with lower eliciting allergen doses and more severe symptoms.

CONCLUSION

Oral FCs bear a risk of severe reactions at all dose levels. Doses of 3-5 mg protein induced symptoms in up to 10% of children allergic to milk or egg. However, food-specific IgE levels are of limited clinical value for the estimation of FC reactions.

Teste de provocação oral aberto na confirmação de alergia ao leite de vaca mediada por IgE: qual seu valor na prática clínica?

OBJETIVO: Revisar os principais protocolos de padronização para o teste de provocação oral aberto aplicado a crianças com suspeita de alergia ao leite de vaca mediada por imunoglobulina E. FONTES DE DADOS: Foram selecionados artigos publicados, nos últimos dez anos, nas bases de dados Medline, Lilacs e SciELO, utilizando-se os descritores de assunto: "hipersensibilidade alimentar", "leite de vaca", "alergia ao leite de vaca", "teste de provocação oral", "crianças" e "diagnóstico". SÍNTESE DOS DADOS: O teste de provocação oral é o método mais fidedigno para estabelecer ou excluir o diagnóstico de alergia alimentar e sua forma aberta pode ser a primeira opção, quando apenas reações objetivas são esperadas. O local para realizar o teste deve possuir todos os recursos para tratamento de emergência. Como preparo, o paciente deve seguir dieta de exclusão do alimento suspeito e descontinuar o uso de medicamentos que possam interferir no resultado do teste. Habitualmente, utilizam-se 8 a 10g de leite em pó ou 100mL de leite fluido, oferecidos em volumes progressivos, a intervalos de dez a 60 minutos. Apesar da rigidez do método, ainda existem situações em que há dificuldade de interpretação dos resultados; por isso, médicos bem treinados devem aplicar o teste, sendo cautelosos ao julgarem as reações. CONCLUSÕES: Mesmo considerando as limitações que dificultam a aplicação do teste de provocação oral na prática clínica, a implementação do teste nos serviços de saúde poderia reduzir diagnósticos falsos-positivos de alergias.

Oral food challenges in children

Many patients assume that allergic reactions against foods are responsible for triggering or worsening their allergic symptoms. Therefore, it is important to identify patients who would benefit from an elimination diet, while avoiding unnecessary dietary restrictions. The diagnosis of food allergy depends on the thorough review of the patients's medical history, results of supplemented trials of dietary elimination, and in vivo and in vitro tests for measuring specific IgE levels. However, in some cases the reliability of such procedures is suboptimal. Oral food challenges are procedures employed for making an accurate diagnosis of immediate and occasionally delayed adverse reactions to foods. The timing and type of the challenge, preparation of patients, foods to be tested, and dosing schedule should be determined on the basis of the patient's history, age, and experience. Although double-blind, placebo-controlled food challenges(DBPCFC) are used to establish definitively if a food is the cause of adverse reactions, they are time-consuming, expensive and troublesome for physician and patients. In practice, An open challenge controlled by trained personnel is sufficient especially in infants and young children. The interpretation of the results and follow-up after a challenge are also important. Since theses challenges are relatively safe and informative, controlled oral food challenges could become the measure of choice in children.

When doctors disagree: a qualitative study of doctors' and parents' views on the risks of childhood food allergy

OBJECTIVE

To examine the views of doctors which underpin clinical practice variation concerning an uncertain health risk, and the views of parents who had sought advice from these doctors, using the example of childhood food allergy.

STUDY DESIGN

Qualitative study involving in-depth interviews and participant observation over 16 months. Focus groups and consultation audio-recordings provided corroborative data.

SETTING

Three specialist allergy clinics located in one metropolitan area.

PARTICIPANTS

Eighteen medical specialists and trainees in allergy, and 85 parents (from 69 families) with food allergic children.

RESULTS

Doctors expressed a spectrum of views. The most divergent views were characterized by: scientific scepticism rather than precaution in response to uncertainty; emphasis on quantifiable physical evidence rather than parental histories; professional roles as providers of physical diagnosis and treatment rather than of information and advocacy; libertarian rather than communitarian perspectives on responsibility for risk; and values about allergy as a disease and normal childhood. Parents held a similar, but less divergent range of views. The majority of parents preferred more moderate doctors' views, with 43% (30 of 69) of families expressing their dissatisfaction by seeking another specialist opinion. Many were confused by variation in doctors' opinions, preferring relationships with doctors that recognized their concerns, addressed their information needs, and confirmed that they were managing their child's allergy appropriately.

CONCLUSIONS

In uncertain clinical situations, parents do not expect absolute certainty from doctors; inflexible certainty may not allow parental preferences to be acknowledged or accommodated, and is associated with the seeking of second opinions.

Diagnosis of food allergy in children: toward a standardization of food challenge

Adverse reactions to food represent a common complaint in childhood; however, only a small proportion of children have proven clinically relevant food allergy. The foods most commonly involved in food allergy are cow's milk, hen's eggs, peanuts, tree nuts, seeds, soy, wheat, fish, and crustaceans. The diagnostic workup of suspected food allergy includes the patient's history, skin prick testing, the measurement of food-specific immunoglobulin E antibodies, and, more recently, the atopy patch test. Because none of these parameters can accurately predict tolerance, the gold standard for diagnosing food allergy is still the double-blind, placebo-controlled food challenge. Although numerous efforts have been made to standardize the procedure, there is a need for improvement. This review presents the current status of the indication and performance of controlled oral food challenges in children with suspected food-related symptoms. It covers aspects of indications and contraindications, blinding, diet before the challenge, the practical performance, the handling of medication, the interpretation of test results, suitable locations for testing, safety considerations, and the procedure after a period of avoidance. Efforts to standardize oral food challenges to achieve the best possible decision on a diet are important to avoid an unnecessary diet that may be harmful to the child.

Utility of the ratio of food-specific IgE/total IgE in predicting symptomatic food allergy in children

BACKGROUND

Double-blind, placebo-controlled food challenges are time-consuming, expensive and not without risk to patients. Therefore, an in vitro test that could accurately diagnose food allergy would be of great value.

OBJECTIVE

To evaluate the utility of the ratio of specific immunoglobulin E (IgE)/total IgE compared with specific IgE (sIgE) alone in predicting symptomatic food allergy.

METHODS

We retrospectively analysed 992 controlled oral food challenges performed in 501 children (median age 13 months). The ratio of sIgE/total IgE was calculated and tested for correlation with the outcome of food challenges. Receiver operator characteristics (ROC)-curves were performed; predicted probabilities and predictive decision points were calculated.

RESULTS

A significant correlation was found between the ratio and the outcome of food challenges for cow's milk (CM), hen's egg (HE), and wheat, but not for soy. The ROC and predicted probability curves as well as sensitivity and specificity of the decision points of the ratio were similar to those of sIgE levels for CM, HE and wheat.

CONCLUSION

In view of the greater effort needed to determine the ratio, without benefit compared with the sIgE alone, the calculation of the ratio of sIgE/total IgE for diagnosing symptomatic food allergy offers no advantage for CM, HE, wheat or soy. For the majority of cases controlled oral food challenges still remain the method of choice.

Controlled oral food challenges in children--when indicated, when superfluous?

The diagnostic work-up of suspected food allergy includes the skin prick test (SPT), the measurement of food specific immunoglobulin E (IgE) antibodies using serologic assays, and more recently the atopy patch test (APT). For specific serum IgE and the SPT, decision points have been established for some foods allowing prediction of clinical relevance in selected cases. The APT may be helpful, especially when considered in combination with defined levels of specific IgE. Controlled oral food challenges still remain the gold standard in the diagnostic work-up of children with suspected food allergy. Most food allergic children will lose their allergy over time. As there is no laboratory parameter, which can accurately predict when clinical tolerance has been developed, controlled oral food challenges are the measure of choice. In this article, the current knowledge of predictors for the outcome of oral food challenges is reviewed and proposals for the daily practical work-up in the case of suspected food related clinical symptoms are presented.

The SAFE project: 'plant food allergies: field to table strategies for reducing their incidence in Europe' an EC-funded study

The true prevalence of food allergy as an IgE mediated reaction is still under discussion. Using apple as a model allergen source a multidisciplinary consortium worked together at developing various strategies for reducing the incidence of fruit allergies in an EC-funded project. Patient allergen profiles were established using in vitro and in vivo tests with respect to geographic area and mild or severe symptoms. Apple allergens (Mal d 1-Mal d 4) were characterised, variants identified, cloned and sequenced. These individual allergens were used to increase the sensitivity and specificity of diagnosis. Furthermore, they provided better prognosis of disease severity. RT-PCR and ELISA were developed for determining the allergen specific mRNA and expressed allergenic protein in a large number of apple cultivars. Similarly, changes in allergen characteristics from harvest through storage to processing and the impact of agronomic practices were investigated. Allergen genes were mapped on a molecular linkage map of apple. The biological function of Mal d 1 was studied using the RNA interference strategy. Finally, consumer attitudes in Northern, Central and Southern Europe were gauged on the acceptability of low allergen cultivars or a GMO and its impact on product quality.