EXAMPLE PAGE - GUIDE - ALLERGY TESTING - Flipbook - Sida 2
Overview of IgE Testing for Allergens
Clinical Pathology Laboratories (CPL) offers blood tests that measure levels of Immunoglobulin
E (IgE) against specific allergens such as foods, inhalants, medications, latex, and venoms. These
tests can confirm the diagnosis of an allergic disorder, supplementing a clinical history consistent
with an immediate allergic reaction.
Health care providers often need to evaluate allergic disorders such as allergic
rhinoconjunctivitis, asthma, and allergies to foods, drugs, latex, and venom, both in the
hospital and in the clinic. Unfortunately, some symptoms, such as chronic nasal symptoms,
can occur in both allergic and nonallergic disorders, and this overlap can confound the
diagnosis and therapy. Studies suggest that when clinicians use the history and physical
examination alone in evaluating possible allergic disease, the accuracy of their diagnoses
rarely exceeds 50%.1
Blood tests are available through CPL that measure immunoglobulin E
(IgE) directed against specific antigens. These in vitro tests can be
important tools in assessing a patient whose history suggests
an allergic disease.2 However, neither allergy skin
testing nor these blood tests are intended to be used
for screening: they may be most useful as confirmatory
diagnostic tests in cases in which the pretest clinical impression
of allergic disease is high.
ALLERGY IS MEDIATED BY IgE
In susceptible people, IgE is produced by B cells in response to specific antigens such as foods, pollens, latex,
and drugs. This antigen-specific (or allergen-specific) IgE circulates in the serum and binds to high-affinity
IgE receptors on immune effector cells such as mast cells located throughout the body. Upon subsequent
exposure to the same allergen, IgE receptors cross-link and initiate downstream signaling events that trigger
mast cell degranulation and an immediate allergic response—hence the term immediate (or Gell-Coombs type I)
hypersensitivity.3
COMMON MANIFESTATIONS OF TYPE I HYPER-SENSITIVITY
REACTIONS INCLUDE SIGNS AND SYMPTOMS THAT CAN BE:
• Cutaneous (eg, acute urticaria, angioedema)
• Respiratory (eg, acute bronchospasm, rhinoconjunctivitis)
• Cardiovascular (eg, tachycardia, hypotension)
• Gastrointestinal (eg, vomiting, diarrhea)
• Generalized (eg, anaphylactic shock).
By definition, anaphylaxis is a life-threatening reaction that occurs
on exposure to an allergen and involves acute respiratory distress,
cardiovascular failure, or involvement of two or more organ systems.4
