Suggested approaches for research protocols involving the potential for life-threatening reactions

General paediatricians and the case of resolving peanut allergy

Children with peanut allergy are almost always advised to avoid nuts for life. There have been recent reports from academic centres that in some cases the allergy might resolve and thus these dietary restrictions can be lifted. To evaluate resolution of peanut allergy in a selected group of children in a general paediatric setting. Children 4-16 yr old with a clear history of an allergic reaction to peanuts who had not had any reaction in the previous 2 yr were eligible. Specific immunoglobulin E (IgE) or skin prick test (SPT) at the time of diagnosis was sought. A SPT and specific IgE was then done and if this was <or= 8 mm and <or= 17.5 kU[A]/l respectively, a double-blind placebo-controlled food challenge was undertaken. A negative challenge consisted of tolerance to a cumulative dose of 15.8 g peanuts followed by an open challenge. From the 82 case notes reviewed 54 children were eligible to participate. Twenty-nine agreed to participate and underwent SPT (29) and specific IgE (28). Of these children eight were eligible for food challenge. Four challenges were negative and four positive. Peanut allergy may resolve in approximately 15% of selected children attending an allergy clinic run by general paediatricians in a district general hospital. Food challenge constitutes the appropriate way of removing the burden that comes with a diagnosis of peanut allergy and enables dietary restriction to cease.

From venom to pain research: a novel use of a scorpaenidae venom

The algesic properties of nocitoxin--a single monomeric, soluble protein responsible for significant algesia--were assessed through human bioassay to gauge nocitoxin's potential for use as a clinical pain stimulus. The hypothesis guiding this study stated that subjects tested with crude bullrout venom or nocitoxin will report experience of pain consistent with chemically induced nociception. To test this hypothesis, sterile solutions of crude bullrout venom, nocitoxin, and pooled nonalgesic proteins were applied to the volar aspect of the forearm of human volunteers in a single-blind study. The resultant pain experiences were recorded using a visual analogue scale and a modified version of the McGill pain questionnaire. Data were assessed for significance using multivariate analysis. Pain responses to crude venom and nocitoxin were significantly greater than pain responses to negative controls (visual anologue scale (VAS), P = 0.001; McGill P = 0.01). Bullrout venom and nocitoxin elicit a similar quality and intensity of pain and represent sensitive, measurable, reproducible stimuli in the absence of observable tissue injury. Therefore, nocitoxin may serveas a suitable stimulus for clinical pain research.

Beef allergy: a review of 12 cases

BACKGROUND

Although beef allergy has long been considered a rare condition, the number of studies regarding the nature, epidemiology, and symptoms of beef allergy has been increasing. We aimed to describe the results of allergy work-up of 12 patients who have a convincing history of acute allergic symptoms following beef ingestion.

METHODS

Detailed histories of 10 children and two adult relatives were obtained and patients underwent skin prick tests with commercial beef extract, raw beef and cooked beef. Serum total and beef-specific IgE were measured. Labial, and in selected cases, open food challenges were undertaken.

RESULTS

Interestingly, the rate of family history of beef allergy was 67% (8/12). Three patients (two with commercial extract, and one with cooked beef) had positive skin test responses to beef. Ten (83%) patients had elevated serum IgE concentrations (median 316.5 kU/l, range 9-1321 kU/l) and the beef-specific IgE was positive in all patients (median 6.23 kUA/l, range 0.83-36.6 kUA/l). Labial food challenge was positive in four (30%) patients. Of the five patients who underwent open food challenges, three were positive and two tolerated the beef administered.

CONCLUSIONS

We conclude that skin prick tests do not accurately diagnose IgE-mediated sensitization to beef. Thus, patients with suspected beef allergy should be screened additionally for beef-specific IgE antibodies, and in selected cases oral food challenge should be carried out to verify the diagnosis.

A novel wheat gliadin as a cause of exercise-induced anaphylaxis

BACKGROUND

Food-dependent, exercise-induced anaphylaxis is a severe form of allergy; the reaction is caused by ingestion of a specific food before exercise. This disorder often escapes diagnosis because neither the ingested food nor the exercise alone induces the symptoms.

OBJECTIVE

The aim of the study was to characterize the allergens involved in wheat-dependent, exercise-induced anaphylaxis and to describe the clinical outcome in a series of 18 adult patients.

METHODS

All 18 patients had experienced recurrent episodes of generalized urticaria during exercise, 17 patients in association with collapse and 15 patients with an anaphylactic reaction. The symptoms appeared only when the patients had eaten food containing wheat before exercise. Wheat allergens were detected by immunoblotting, purified by gel filtration and reversed-phase chromatography, and subjected to N-terminal sequencing. The IgE-binding ability of the purified proteins was studied by ELISA, and their in vivo reactivity was studied by skin prick testing.

RESULTS

IgE antibodies from pooled patient sera were bound to 65-kd and 40-kd wheat proteins in immunoblotting. The 65-kd allergen was a previously undescribed wheat protein, showing 61% sequence identity to gamma-gliadin, whereas the 40-kd allergen had 100% identity to alpha-gliadin. In ELISA, all 18 patients showed elevated IgE levels to the novel gamma-like gliadin, and 13 of the patients showed elevated IgE levels to the alpha-gliadin. None of the 54 control subjects with wheat allergy, urticaria, or coeliac disease had IgE antibodies to the gamma-like gliadin. The in vivo reactivity of the gamma-like gliadin was verified by positive skin prick test responses in all of the 15 patients who were tested. During the follow-up on a gluten-free or wheat-free diet, 3 patients experienced reactions after having unknowingly eaten wheat before exercise, but all the other patients who were adhering to the diet remained symptom-free.

CONCLUSION

This study shows that wheat is a frequent cause of food-dependent, exercise-induced anaphylaxis and suggests that the major allergen is a previously undescribed gamma-like gliadin. For screening of this life-threatening allergy, we recommend skin prick testing with crude gliadin and we recommend a gluten-free diet for treatment.

Resolution of peanut allergy: case-control study

OBJECTIVES

To determine whether there are any differences between children who remain mildly or moderately allergic to peanut and children with similar histories but a negative reaction on challenge with peanut.

DESIGN

Case-controls matched for age and sex.

SETTING

Children's day wards in two teaching hospitals.

INTERVENTION

Open food challenge with peanut.

SUBJECTS

15 children with resolved peanut allergy (resolvers) and 15 with persistent allergy (persisters).

MAIN OUTCOME MEASURE

Reaction on challenge with peanut, serum total and peanut specific IgE concentrations.

RESULTS

The groups had a similar median age at first reaction to peanut (11 months, range 5-38) and similar symptoms. Allergy to other foods was less common in resolvers (2/15) than persisters (9/15) (P=0.02). On skin prick testing with peanut all 13 resolvers tested but only 3/14 persisters had a weal of <6 mm (P<0.0001). Total and peanut specific IgE concentrations did not differ much between the groups.

CONCLUSION

Appropriately trained clinicians must be prepared to challenge preschool children with peanut as some will be tolerant despite a history of reactions to peanut and a positive skin prick test with peanut. Preschool children whose apparent peanut allergy is refuted by food challenge show allergy to other foods less often than those in whom peanut allergy persists. The size of weal on skin prick testing to peanut predicts reactivity but not severity on peanut challenge.

An evaluation of the sensitivity of subjects with peanut allergy to very low doses of peanut protein: a randomized, double-blind, placebo-controlled food challenge study

BACKGROUND

The minimum dose of food protein to which subjects with food allergy have reacted in double-blind, placebo-controlled food challenges is between 50 and 100 mg. However, subjects with peanut allergy often report severe reactions after minimal contact with peanuts, even through intact skin.

OBJECTIVE

We sought to determine whether adults previously proven by challenge to be allergic to peanut react to very low doses of peanut protein.

METHODS

We used a randomized, double-blind, placebo-controlled food challenge of 14 subjects allergic to peanuts with doses of peanut ranging from 10 microg to 50 mg, administered in the form of a commercially available peanut flour.

RESULTS

One subject had a systemic reaction to 5 mg of peanut protein, and two subjects had mild objective reactions to 2 mg and 50 mg of peanut protein, respectively. Five subjects had mild subjective reactions (1 to 5 mg and 4 to 50 mg). All subjects with convincing objective reactions had short-lived subjective reactions to preceding doses, as low as 100 microg in two cases. Five subjects did not react to any dose up to 50 mg.

CONCLUSION

Even in a group of well-characterized, highly sensitive subjects with peanut allergy, the threshold dose of peanut protein varies. As little as 100 microg of peanut protein provokes symptoms in some subjects with peanut allergy.