A new blood test for Lyme disease may provide a more accurate method for detecting the tick-borne illness, particularly in its early stages when current tests may not yield an accurate diagnosis. A researcher from The Children's Hospital of Philadelphia has used a method that detects telltale proteins that often remain hidden from routine blood tests for Lyme disease.
In a patient who had a "bull's-eye" skin rash often found in early Lyme
disease, but who tested negative for the disease in three standard blood
tests, the new test detected a protein called OspA. OspA is an antigen, a
substance that stimulates an immune response, and is produced specifically by
Borrelia burgdorferi, the microorganism that causes Lyme disease.
The patient had already tested positive for Lyme disease after a culture
was taken from a skin biopsy. However, this technique is performed only at a
few specialized facilities, is more invasive than a blood test, and is not
practical for large-scale testing. "Our technique is practical for detecting
the Lyme antigen in patients who test negative for the disease in the
currently available blood tests," said Michael Brunner, Ph.D., of the Division
of Rheumatology at The Children's Hospital of Philadelphia. Dr. Brunner's
paper appears in the March issue of the Journal of Immunological Methods.
Although the results reported in the current paper describe a test in only
one patient, the research builds on previous work by Dr. Brunner showing the
presence of OspA in more than 20 patients with different stages of Lyme
A recurrent worry for residents of the Northeastern U.S. and other
regions, Lyme disease may present diagnostic puzzles. Other diseases, such as
rheumatoid arthritis, may cause joint pains of the sort found in Lyme disease.
The famous "bulls-eye" rash associated with Lyme disease occurs only in 60 to
80 percent of patients, and may fade before a patient sees a physician. For
these reasons, along with inaccuracies in the current blood tests, Lyme
disease has been called one of the most overdiagnosed and underdiagnosed
Overdiagnosis occurs because current blood tests, which test for the
disease indirectly by seeking antibodies produced by a patient's immune
system, are not always specific for Lyme disease. Microorganisms not causing
Lyme disease may give rise to the same antibodies, and false positive test
results may occur. In addition, false positives may occur when a blood test
detects residual antibodies to Lyme disease lingering in the blood long after
the disease is cured.
However, false negatives may also occur because current blood tests for
Lyme disease are not sensitive enough. "Early in the disease, antibodies
against Lyme disease may not be detectable because they are sequestered in
immune complexes in the blood," says Dr. Brunner. In immune complexes, antigen
from the invading microorganism binds to the antibodies that respond to the
The technique used by Dr. Brunner isolates the immune complexes from the
patient's blood sample, captures the antibodies inside, then detaches and
identifies the antigen -- the component that originated in the disease-causing
microorganism. "We identified at least one of the antigens as OspA, which is a
smoking gun for Lyme disease," said Dr. Brunner. "The test can identify early
disease, and also can distinguish active disease from evidence in the blood of
a past disease."
Much additional work would be necessary to transform this finding into a
large-scale, commercially available test. Additionally, said Dr. Brunner, the
technique may be useful in studies of other diseases that exhibit immune
complexes, such as lupus, infectious hepatitis and multiple sclerosis.
Vidyya readers interested in additional information regarding the new test may contact Erin McDermott of Children's Hospital of Philadelphia,
+1 215 590 7429, or firstname.lastname@example.org.