Background: PhadiatopTM is a commercially available qualitative serological test employed for screening of allergic sensitization in patients with suspected allergic diseases. Aim: The study evaluated the diagnostic accuracy of PhadiatopTM for the diagnosis of allergic sensitization in a general adult population.

Methods: A total of 469 subjects from the population of A-Estrada (Spain) were selected by age-stratified random sampling (age range, 18-92 years). PhadiatopTM test (Uni-CAP method) was performed in serum samples from 465 of these subjects. Skin prick tests to a panel of 13 relevant aeroallergens in the studied area (including mites, pollens,
moulds, and animal dander) were employed as the reference diagnostic procedure. Subjects with at least a positive skin prick test (≥4 mm, n= 120) were considered to have allergic sensitization.

Results: PhadiatopTM sensitivity was 70.8% (95% CI 61.7-78.6%), specificity 90.7% (95% CI 87.0-93.5%), positive predictive value 72.6% (95% CI 63.5-80.3%), negative predictive value 89.9% (95% CI 86.2-92.8%), global accuracy 85.6% (95% CI 82.0-
88.6%), negative likelihood ratio 0.3 (95% CI 0.2-0.4), and positive likelihood ratio 7.6(95% CI 5.4-10.8). A high proportion of false-positive PhadiatopTM cases showed (a) increased total serum IgE levels, (b) significant alcohol consumption, and (c) small-sized (below the diagnostic cut-off) wheal reactions on SPT. A high proportion of false-negative PhadiatopTM cases showed exclusive storage mite sensitization. Sensitivity and positive predictive value of PhadiatopTM were somewhat higher among individuals with a history of nasal or bronchial symptoms.

Conclusions: PhadiatopTM is a valuable tool for the diagnosis of allergic sensitization in a general adult population. However, limitations of the test should be taken into account in similar surveys.

Key Words: Atopy, allergic sensitization, prick-tests, specific IgE, Phadiatop, sensitivity, specificity.