Laboratory Methods in Allergology - Identification and Quantification of Specific IgG Antibodies

Allergic diseases represent increasing health problems worldwide, and symptoms may not be easily distinguished from other disorders. The term hypersensitivity is defined as a reaction that induces reproducible symptoms and signs, initiated by exposure to a defined stimulus at a dose tolerated by normal subjects. Hypersensitivity can be differentiated into IgE and non-IgE allergic hypersensitivity as well as non-allergic hypersensitivity, which does not involve the immune system. Most patients are sensitised to more than one allergen which might trigger clinical symptoms, and often it is difficult to identify the major allergen. In addition, the presenting symptoms are dependent on current inflammation, presence of infection, physical and psychological stress and hormonal influences. Different tests may be used to distinguish between these conditions. An allergic hypersensitivity is usually IgE-mediated but may involve IgG antibodies. In this article we explore currently available tests and highlight their applications and limitations.