Lovers running joyously through fields of ragweed, grown
men rolling around in the grass like children — characterize
just a few of the allergy medication ads you may be familiar
with. These days, there seem to be more and more allergy
drugs available — the numerous ads alone are a good
indication of the increase in their numbers. But does
this trend reflect an increase in allergy sufferers too?
A study on a newly developed, and considerably more accurate,
allergy test indicates that the prevalence of allergies
may truly be on the rise.
The ImmunoCAP test detects and
measures the level of allergen-specific IgE in blood
samples. Unlike skin-based tests, these new screens
are not affected by the presence of histamines. As well,
the company claims that ImmunoCAP is more accurate than
the more established blood-based radioallerosorbant
test, which is less sensitive than skin tests.
ART
vs SCIENCE
"Diagnosing allergies has been somewhat of an art form
and susceptible to bias until now," remarked Dr P Brock
Williams, PhD, a clinical professor of allergy immunology
at Children's Mercy Hospital in Kansas, in a Medscape
interview following his presentation at the 61st Annual
Meeting of the American Academy of Allergy, Asthma &
Immunology in Texas.
Until now, the significance of
the reported increase in allergies in the industrialized
world has been unclear. The rise may be artifactual
- due to better reporting, better testing, or increased
awareness on the part of patients — or real, due
to a changing environment and/or lifestyle.
To test ImmunoCAP's diagnostic
chops and to probe the nature of allergy prevalence,
Dr Williams recruited families that had at least one
parent with reversible airway disease. The study population
of 1,471 included 667 parents and 804 kids. They were
tested for the presence of IgE that's specifically produced
in immune reactions to several common allergens.
"IgE is the factor in the blood
that is responsible for producing symptoms of allergies,"
explained Dr Williams in his presentation. "An increase
in allergy and asthma should be reflected in IgE levels."
The results given below look specifically at dust mite
allergies.
Of the subjects tested, 45.3% of
the parents tested positive (defined as more than 0.35kU/L)
for mite-specific IgE, while 60.1% of their kids proved
positive. When the actual antibody levels in parents
and their kids were determined, Dr Williams found that,
in sensitized parents,
the average mite-specific IgE level
was 14.8kU/L. But, in sensitized children, the level
was far higher, averaging 51.7 kU/L. Moreover, while
only 10% of parents had mite-specific IgE levels above
100 kU/L, a whopping 42% of the kids did.
The ImmunoCAP test "provides ...
physicians with an objective tool to accurately diagnose
allergies and determine treatment strategies," remarks
Dr Sheryl Szeinbach, of Ohio State University, who has
also researched the technique.
Presented Mar 21, 2005 at the American
Academy of Allergy, Asthma & Immunology Meeting
|
