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

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.

Comparación de phadiatop y pruebas cutáneas en 130 pacientes con sospecha de rinitis alérgica

AIM

To establish the degree of coincidence in the results obtained from allergic skin-tests (prick-test) and the screening determination of specific IgE (Phadiatop) on a sample of patients with suspected allergic rhinitis (AR).

MATERIAL AND METHODS

Prospective study of 130 patients with suspected AR, on whom we carried out prick-test and Phadiatop, comparing the results of both tests.

RESULTS

The results of both tests were similar in 118 patients (89%). There were false negatives and false positives with both methods.

CONCLUSIONS

The diagnosis of AR is based on a precise clinical history, complemented with prick-testing. The prick-test is considered the main test for the diagnosis of AR. In selected cases it is indicated to complete the study with the determination of serum specific IgE against the suspected allergens. The Phadiatop test is a specific IgE test for multiple allergens being its main use as a screening test in AR, mainly for outpatient cases.

The diagnosis of allergic rhinitis: how to combine the medical history with the results of radioallergosorbent tests and skin prick tests

OBJECTIVE

To identify the most useful combinations of symptoms and the results of radioallergosorbent tests (RASTs) and skin prick tests (SPTs) for the diagnosis of allergic rhinitis.

DESIGN

A prospective comparison was made of symptoms and the results of RASTs and SPTs with 7 different nasal allergies; the references used were the "consensus diagnoses" provided by 3 experts.

SETTING

Nineteen general practices in The Netherlands.

PATIENTS

365 consecutive patients aged 12 or over who visited their general practitioner because of chronic or recurrent nasal symptoms between 1 March 1990 and 1 March 1991.

MAIN OUTCOME MEASURES

The most useful combinations of items from the history, RASTs, and SPTs, for the diagnosis of 7 different nasal allergies; the predictive probabilities of these combinations.

RESULTS

Diagnostic criteria could be drawn up resulting in a near-perfect discrimination between patients diagnosed as having allergic rhinitis and patients diagnosed as not having allergic rhinitis. Most of these criteria combined only a single item from the history with either RAST or SPT. For nearly all nasal allergies, both the negative predictive probabilities and the positive predictive probabilities were 97% or more.

CONCLUSIONS

The common nasal allergies can be diagnosed with a very high certainty with the aid of simple diagnostic criteria. Data from a strictly limited case history combined with either RAST or SPT are sufficient.

Nasal smear eosinophilia for the diagnosis of allergic rhinitis and eosinophilic non-allergic rhinitis

OBJECTIVE

To evaluate nasal smear eosinophilia for the diagnosis of allergic rhinitis and eosinophilic non-allergic rhinitis in general practice.

DESIGN

Nasal smear eosinophilia was assessed and compared with 'consensus diagnoses' made by three experts in a modified Delphi method.

SETTING

Nineteen general practices in The Netherlands.

SUBJECTS

363 consecutive patients aged 12 years or over who visited their general practitioner because of chronic or recurrent nasal symptoms between 1 March 1990 and 1 March 1991.

MAIN OUTCOME MEASURES

The predictive value of nasal smear eosinophilia for allergic rhinitis; the prevalence of eosinophilic non-allergic rhinitis.

RESULTS

The positive predictive value of nasal smear eosinophilia (> or = 10% eosinophils) for allergic rhinitis was 30/37 = 81% (95% confidence interval (CI): 65-92%), the negative predictive value 172/312 = 55% (95% CI: 50-61%). Addition of the result of nasal smear eosinophilia to the information that was already obtained from the medical history resulted in a significant but very small improvement in the discrimination between patients with and without allergic rhinitis. The prevalence of eosinophilic non-allergic rhinitis was 7/349 = 2.0% (95% CI: 0.8-4.1%).

CONCLUSION

Nasal smear eosinophilia contributes significantly to the diagnosis of allergic rhinitis; however, this contribution is very small and considered clinically irrelevant. Eosinophilic non-allergic rhinitis has a low prevalence; identifying this disorder is of minor importance. In conclusion, nasal smear eosinophilia is not recommended for use in general practice.