The utility of specific immunoglobulin E measurements in primary care

Abstract

Background: The identification of atopic patients may not be considered a necessary step in the diagnosis process in primary care. This study investigated the impact of the addition of a specific immunoglobulin E (IgE) antibody test on the current management by primary-care physicians of patients with respiratory and skin symptoms.

Methods: The study had a prospective before-after design. It was conducted in two geographic areas of Italy and Spain and consisted of two parts, Part I and Part II. In each part patients were recruited according to inclusion and exclusion criteria. After the clinical examination, the patients were classified into one of the following categories using a physician's classification: allergic, nonallergic or uncertain. A blood sample was taken from each included patient for specific IgE antibody determination using a Pharmacia CAP System, including either Phadiatop Infant (0-5 years of age) or Phadiatop and food mix (fx5e) (>5 years of age). If a positive result was found, an additional 6-26 specific IgE tests were performed. In Part I the result of the specific IgE antibody determinations was not available before the physician's classification was made. In contrast, in Part II, the result of the IgE test was available at the time when the physician's classification was made. Between Part I and Part II an educational intervention for physicians to improve their knowledge of blood testing for IgE-mediated allergy was carried out.

Results: A total of 721 patients were included in the study. The agreement between classifications based on clinical data and IgE antibody results changed from a kappa coefficient of 0.13 in Part I to 0.86 in Part II. With regard to the allergic status the proportion of uncertain cases was reduced from 26.3% in Part I to 4.1% in Part II. The proportion of patients that were advised to avoid allergens increased from 18% in Part I to 62% in Part II in the group of patients classified both by the clinician and the IgE test.

Conclusions: The use of specific IgE antibody determinations improves the clinical management of patients with allergy related symptoms in primary care, allowing advice to be given on specific allergen avoidance. However, the applicability of this diagnostic tool in different areas and countries should be further assessed in cost-effectiveness studies.