Denver hospital develops a blood
test to protect against allergic reactions to hip and knee implants
BY NSIKAN AKPAN | MAY 15,
2013 12:35 AM EDT FiDA highlight
A new allergy exam from physicians at National
Jewish Health in Denver could prevent thousands of hip and knee implants from
being rejected by their recipients. The procedure is presented in a study released today
in the Journal of Allergy and Clinical Immunology.
Of the 1 million hip and knee replacements that
occur each year, about 100,000 -- or 10% -- will fail because of an allergic reaction. Most reactions
are caused by the metallic
materials used in the implants or bone cement used in surgery.
The symptoms start shortly after the procedure.
"I had horrible itching and intense pain
throughout my body," said Paula Spurlock, a patient at National Jewish
Health who discovered she was allergic to her implant in 2011.
"I couldn't take it. Every single
thing in me itched."
Joint replacements are typically made from metal,
plastic, or ceramic. Patients need to know if they have an allergy before they
have surgery, so they can decide which type of implant to put into their
bodies.
The current procedure for assessing metal
allergies is to administer a skin patch test. A liquid mixture of the potential
offending agent is wiped on a pad that is taped to the skin for approximately
72 hours. If a reaction occurs, then the person is allergic.
The main problem with the skin patch test is its
duration. A person who has broken their hip, especially if they are elderly, is
dealing with a serious medical emergency and may not have the 3 to 5 days that
it takes to conduct a skin test. Plus some hospitals aren't equipped or staffed
to perform the procedure.
The researchers decided to develop a simple blood test that
could detect allergies to nickel, a common material used in joint implants.
There are many advantages to using a blood test.
"First of all it's much easier," said
lead author Dr. Karin Pacheco, an allergist at National Jewish Health.
"You can send the blood in and it will get developed quickly, and you
won't need to have somebody available who knows how to do the patch
testing."
To validate its accuracy, they compared it in a
side-by-side analysis to the skin patch test.
This
innovative allergy exam could identify people with nickel allergies about 70%
of the time relative to the skin patch test and had an accuracy of 98% at
distinguishing people without allergies.
While more analysis is needed, this new blood test could help
thousands of patients in the coming years. More than 11,000 people a day are expected to have
implant surgeries by 2030, so the demand, from a public health
perspective, would be enormous.
The authors hope the blood test will be approved
and widely used in the next couple of years.
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