Diagnosis of allergy in different age groups of children: use of mixed allergen RAST discs, Phadiatop and Paediatric Mix

Cumulative IgE-levels specific for respiratory allergens as biomarker to predict efficacy of anti-IgE-based treatment of severe asthma

Molecular therapies, including anti-IgE, biologicals and small molecules are increasingly used for treatment of asthma. The effectiveness of these therapies may be increased with biomarkers. Aim of this study was to assess the value of measuring cumulative IgE levels specific for respiratory allergens to increase the efficacy of anti-IgE therapy for severe bronchial asthma. One hundred and thirty seven patients with severe asthma were recruited from 2016 to 2022. Standard empirical allergy diagnosis (i.e., anamnesis, skin testing, allergen-specific IgE measurement), blood eosinophil counting, measurement of total IgE and of cumulative IgE-specific for respiratory allergens by Phadiatop™ were performed. Thirty four patients with severe allergic asthma, for whom all three diagnostic methods were performed, were then used to analyze the efficacy of anti-IgE treatment in patients stratified in two groups according to cumulative IgE levels specific for respiratory allergens determined by Phadiatop™. Group #1 patients (n = 8) had cumulative specific IgE values ≥ 0.35 and < 1.53 PAU/l while in group #2 patients (n = 26) they were ≥ 1.53 PAU/l. Treatment with Omalizumab was performed for at least 12 months. The level of asthma control (ACT questionnaire), the number of asthma exacerbations, the quality of life (AQLQ questionnaire), the need for systemic corticosteroids, and the respiratory function (FEV1) was determined by “before-after” analysis for each group, followed by a comparison of the dynamics between groups. In group 2 patients with an initial allergen-specific IgE level ≥ 1.53 kUA/L, the efficacy of Omalizumab treatment was better regarding asthma control, number of exacerbations, and quality of life than in group 1 patients. Our study provides evidence that measuring cumulative levels of IgE specific for respiratory allergens could be a useful screening method for detecting an allergic phenotype of severe asthma and may serve as biomarker to enhance the success of IgE-targeted therapy.

Skin prick test and tonsil size in children: any relation?

We hypothesized, allergic reactions of the tonsillar mucosa may cause secondary lymphoid hypertrophy in children. To evaluate this, we compared tonsil sizes and skin prick test results. Children of ages 6-12 years were divided into two groups according to the results of the skin prick tests (SPT), as atopic and non-atopic groups. All tonsil sizes were evaluated by the same observer using the Brodsky L. Scala. No statistically meaningful difference was found between the tonsil sizes of the atopic and the non-atopic groups of children. No statistically meaningful correlation was found between tonsil sizes and allergen sensitivity degrees. Even though some highly allergic children were observed to have large tonsils, it was not statistically meaningful. Since no correlation is found between SPT and tonsil sizes, allergy may not be an etiologic factor of tonsillar hypertrophy in children.

A prospective study to determine the incidence of atopy in children undergoing adenotonsillectomy for obstructive sleep apnea

OBJECTIVES

To investigate the relationship between adenotonsillar hypertrophy seen in pediatric obstructive sleep apnea and upper airway allergy to airborne allergens.

METHODS

A prospective study of Radioallergosorbent (RAST) tests to common airborne allergens in children (<16 years old) undergoing adenotonsillectomy for obstructive sleep apnea in a London Teaching Hospital.

RESULTS

20.9% of patients had a positive RAST result to house dust mite, 2.8% to cat hair, 0% to mixed feather, 7.8% to mixed grass pollen and 3.8% to dog hair.

CONCLUSIONS

This study does not support the hypothesis that the adenotonsillar hypertrophy seen in pediatric patients with obstructive sleep apnea is contributed to by allergy to airborne allergens. It is possible that there is a localized allergic reaction in the upper respiratory tract mucosa which is not apparent on an assay of systemic IgE.

ImmunoCAP Phadiatop Infant--a new blood test for detecting IgE sensitisation in children at 2 years of age

BACKGROUND

Correct diagnosis of immunoglobulin E (IgE)-mediated disease is the prerequisite for secondary allergy prevention during early childhood.

OBJECTIVE

To evaluate the diagnostic efficacy of a new blood test, Phadiatop Infant, in detecting IgE sensitisation to food and inhalant allergens among children at 2 years of age.

METHODS

Children (n = 239) were followed prospectively from birth to 2 years of age for the presence of IgE sensitisation and the development of atopic manifestations. Immunoglobulin E sensitisation was evaluated by skin prick test (SPT) and analysis of allergen-specific IgE antibodies in plasma to food and inhalant allergens. The children were classified into three groups: IgE-sensitised, non-IgE sensitised and inconclusive, depending on SPT and allergen-specific IgE results.

RESULTS

Twenty-six (11%) of the children were classified as IgE-sensitised, 182 (76%) as non-IgE sensitised and 31 (13%) as inconclusive. Phadiatop Infant was positive in 50 (21%) of the children. Ten children (4%) with identified IgE antibodies against the selected food and inhalant allergens showed negative Phadiatop Infant. Three children showed positive Phadiatop Infant but were negative in the other tests performed. These results correspond to positive and negative predictive values for Phadiatop Infant of 89 and 99%, respectively. Children with clinical symptoms of atopic diseases had significantly increased levels for Phadiatop Infant (P < 0.01).

CONCLUSION

Phadiatop Infant appears to be a reliable alternative to SPT and the measurement of allergen-specific IgE antibodies in plasma for detecting clinically important IgE sensitisation among children at 2 years of age.

Development of specific immunoglobulin E in coughing toddlers: a medical records review of symptoms in general practice

The aim of this study was to study whether young children, originally immunoglobulin E (IgE) negative and who became sensitized to specific inhalation allergens, presented more frequently to their general practitioner (GP) with other allergy- and asthma-related symptoms than children who remained IgE negative. It was also investigated whether asthma was diagnosed more often in children who developed IgE to inhalant allergens. Coughing children, 1-5 years of age, visiting the participating GPs, were tested for IgE antibodies to mites, dogs, and cats by using radioallergosorbent testing (RAST). All IgE-negative (RAST < 0.2 IU/ml) children were re-tested after 2 years. The medical records of 162 children were reviewed on asthma- and allergy-related symptoms and on prescribed medication. After 30 months, 27 of the 162 children (17%) had become IgE positive for one or more allergens. Most children (93%) had visited their GP for treatment of respiratory symptoms during this period. However, the children who had become IgE positive had visited their GP more often than the children who remained IgE negative. Differences in visits were seen for: shortness of breath (52% IgE-positive vs. 19% IgE-negative children, respectively), wheeze (37% vs. 17%), allergic rhinitis (33% vs. 16%), and pneumonia (22% vs. 8%), but not for coughing (89% vs. 88%). The IgE-positive children were more frequently diagnosed by their GP as having asthma (48%) than were the IgE-negative children (23%). In a multivariate analysis, indicators of becoming IgE positive were: a visit for shortness of breath (odds ratio [OR] = 6.9; 95% confidence interval [CI] = 2.1-23.1) and two or more visits for wheeze (OR = 6.0; 95% CI = 1.9-19.2), adjusted for breast-feeding, age, and asthma or allergy in the family. The positive predictive value (PPV) of being IgE positive with a diagnosis of asthma was 90% (whereas the negative predictive value was 48.0%) for a child attending their GP for treatment of wheeze. For recurrent coughing (six or more visits) and shortness of breath, the PPVs were 73% and 71%, respectively. The development of sensitization to common inhalant allergens is associated with specific allergy and asthma-related symptoms in young children. IgE-positive children were more frequently diagnosed as having asthma by their GP. This implies that in general practice it is possible to detect children at high risk for developing allergic asthma early in life by their respiratory symptoms and by subsequent testing for specific IgE to inhalant allergens.

Efficacy of a single diagnostic test for sensitization to common inhalant allergens

BACKGROUND

UniCAP Phadiatop is a single laboratory test designed to determine the presence or absence of specific IgE to a variety of common inhalants. Its purpose is to aid in the differentiation of patients with symptoms attributable to allergic disease from other common causes.

METHODS

Consecutive children and adolescent patients (n = 145) at two centers were examined by having their history and physical examination performed by two board certified allergists. Their conclusions along with skin prick tests and specific IgE measurements regarding seven common inhalants (mite, oak, ragweed, grass, dog, cat, Alternaria) were compared with UniCAP Phadiatop test results. This was done using concordance of all test results. Attempts to resolve test discrepancies, when found, included specific RAST inhibitions, total IgE values, and physicians' judgment after testing.

RESULTS

All patients with resolved diagnoses (143 of 145, 103 positive and 40 negative) were identified correctly by the UniCAP Phadiatop test. Skin test results and specific IgE measurements correlated well, but neither correlated well with the history by itself, suggesting a minimal false-positive component of the history of 23%. UniCAP Phadiatop results demonstrated a quantitative relationship between the patient's score and the amount of IgE specific to these individual allergens.

CONCLUSIONS

The UniCAP Phadiatop test was shown to be highly sensitive and specific in differentiating individuals who are sensitized to common inhalants from those who are not. This test is recommended to all physicians as an aid in diagnostic and referral decisions for patients suspected of having an inhalant allergic diathesis.

Screening of atopic allergy in 5-year-old children--a comparison of the diagnostic properties of Phadiatop Paediatric and Phadiatop

The ability of Phadiatop Paediatric (PP), Phadiatop (P), mixed-food RAST (MF), and the combination of P and MF to identify children with atopic allergy was evaluated among 193 children who had a family history of atopic disease, and who had an average age of 5 years. If atopy is defined as the presence of at least one positive skin prick test (> or = 2+) to common food and/or inhalant allergens, P had a sensitivity of 86%, a specificity of 94%, and an efficacy of 92%. These figures were somewhat better than the results with PP. However, when P was combined with MF, the sensitivity increased to 89%, but at the expense of lowered specificity (83%) and efficacy (84%). If the tests were related only to clinical signs/symptoms of atopic disease, the sensitivity and efficacy were, at maximum, 63% and 81%, respectively. There was a discrepancy between the results of P and PP in 9% of the children. One explanation of this discrepancy may be that PP seems to be incapable of detecting children with respiratory allergies induced by pollens from birch and related trees. The results indicate that in 5-6-year-old children P should be preferred to PP and to the combination of P and MF for atopy screening, at least in places where birch pollen is a common allergen.

Role of clinical laboratory in allergy testing

The clinical laboratory has a well defined role to play in the diagnosis and management of patients with allergy. Elevated serum levels of total IgE and/or allergen-specific IgE indicate that an IgE mediated event has occurred. Methods such as basophil degranulation and basophil or leukocyte histamine release can provide similar information. Sensitive and precise methods suitable for automation are available for quantitation of histamine in whole blood or plasma. Methyl histamine can be assayed in urine. Eosinophil cationic protein levels in serum can be used as an indicator of eosinophil activation in disorders such as asthma and atopic dermatitis. Similarly, serum mast cell tryptase levels can confirm or exclude an anaphylactic reaction both in life and as a cause of death. This review documents and compares commercially available methods for these assays and discusses their application to screening, diagnosis, and management of patients with allergy.

The Phadiatop test compared with RAST, with the CAP system; proposal for a third Phadiatop outcome: "inconclusive"

In 19 general practices, blood samples were obtained from 361 patients aged 12 years or older with chronic nasal symptoms. The Phadiatop test and a panel of RASTs to common inhalant allergens were performed on all sera with the recently introduced Pharmacia CAP system. The RAST panel was accepted as the standard. The sensitivity of the Phadiatop was 94% (95% confidence interval (CI): 89-97%), the specificity 98% (95% CI: 95-99%), the positive predictive value 97% (95% CI: 94-99%), and the negative predictive value 95% (95% CI: 91-98%). It is noteworthy that these values are very similar to those found in hospital outpatient departments. It was possible to reduce further the small percentage of false outcomes by replacing the cutoff point of the Phadiatop ratio of 1.00 by the two cutoff points 0.75 and 1.15. This resulted in three possible outcomes: a highly predictive positive outcome, a highly predictive negative outcome, and an "inconclusive" outcome. Alternatively, the cutoff point of 1.00 may be maintained while attaching the annotation "borderline" to all positive or negative Phadiatop outcomes where the Phadiatop ratio is between 0.75 and 1.15. By this simple method, physicians are alerted to the possibility of a false outcome; on the basis of the case history and other clinical findings, they can then decide whether further testing should be done.

In vitro screening for inhalant allergy with multi SX 1 RAST (Phadiatop)

A new in vitro screening test for inhalant allergy (Phadiatop, Pharmacia Uppsala, Sweden) was evaluated for its effectiveness in identifying allergic patients. The test is based on the radio-allergo-sorbent-test (RAST). Specific IgE antibodies to different inhalant allergens are detected simultaneously. Serum samples from 300 patients and controls were run with Phadiatop. 96% of 150 patients with proved allergic disease were correctly identified by Phadiatop. 92% of 150 individuals without clinically relevant allergic hypersensitivity were found correctly to be negative. Allergic disease was proved or excluded by case history, skin prick test, RAST and, in some cases, additionally by provocation challenge.

IgE antibody screening in children. Evaluation of the Phadiatop Paediatric

With 200 sera from children, results of the Phadiatop Paediatric test were compared with results of the combination "Phadiatop + mixed-food-RAST". The Phadiatop Paediatric test was found to be efficient for IgE antibody screening in young children, when the results of this test were not solely given as "positive" or "negative", but also as "sample/reference-ratio". Clinical documentation could be obtained retrospectively for 171 children and revealed that 99% of the children with atopic disease were found positive in the Phadiatop Paediatric, 17% of the children who were considered non-atopic on clinical grounds, were positive both in the Phadiatop Paediatric and in the combination "Phadiatop + mixed-food-RAST". It is concluded that an atopic immune response is not always associated with current symptoms.

The Phadiatop test allows adequate screening for atopy with a marked reduction in cost

Sera from 35 patients aged 5 years or younger and sera from 95 patients 6 years and older were assayed for both total IgE level, allergen-specific IgE by RAST and either the Phadiatop Paediatric or Phadiatop procedures, depending on age. Good agreement was found allowing exclusion of specimens anticipated to be RAST negative with an expected reduction in RAST testing of up to 80% of the present workload, without significant exclusion of RAST positive specimens.