Comparison between modified skin prick test with standardized allergen extracts and Phazet

Abstract

Skin prick tests (SPTs) represent one of the most common techniques of skin testing and are of great value, especially when standardized extracts are used. Phazet is a puncture test involving needles coated with standardized allergens. Phazet and SPTs have been compared in 130 subjects tested with six standardized allergen extracts: orchard-grass, olive, and mugwort pollens, cat dander, Dermatophagoides pteronyssinus, and Alternaria. Patients have been carefully selected on the basis of a suggestive clinical history, SPTs, and RAST. For all allergenic species, at least 20 nonsensitive individuals have been tested. The sensitivity (true positive in percent of patients with disease) of Phazet was 99.4%, and its specificity (true negative in percent of patients without disease) was 99.2%. It is concluded that Phazet and SPTs with standardized extracts are equally effective in the diagnosis of immediate-type allergy and that standardized extracts have improved the diagnosis of allergy, especially for previously poorly characterized extracts, such as Alternaria.