Lyme Disease: The Pitfalls of Laboratory Testing
by
John Drulle M.D.
in:
Lyme Disease 1991:
Patient/Physician Perspective from the U.S. and
Canada
Lora Mermin, editor
pg. 34-35
..........
Currently available commercial tests for Lyme disease provide
indirect evidence of exposure to the Lyme bacteria. When someone is infected
with the Lyme bacteria, the immune system responds by making specific
proteins, called antibodies, whose role is to seek out the Lyme bacteria,
attach to them and initiate the process of destruction. In most patients,
these antibodies are unable to destroy the Lyme bacteria (population, addition by J. Gruber), which by methods
which are not completely understood, may remain alive in the human body for
many years, in spite of high "titers" or concentrations of antibodies.
- Detectable levels of these antibodies may not be found until 3 to 8 weeks
after exposure. Significant illness may be present before the test is
positive.
- Most people who present with the characteristic EM (erythema
migrans ) rash of Lyme disease test negative at that time.
- A number of patients clearly do not develop measurable antibodies.
This is usually due to
antibiotics given early in the infection for Lyme or non-Lyme infections.
- There is a significant strain variability in Lyme bacteria isolated in
different geographic areas, and since commercial tests have been developed
from certain isolates, they may be incapable of detecting antibodies to a
different strain of Lyme bacteria.
- It is also possible that some people's
immune systems do not recognize the Lyme bacteria as an invader and do not
produce specific antibody .*
- When there is an excess of Lyme bacteria and
their fragments, they may combine with all the circulating Lyme specific
antibodies. Current commercial antibody tests for Lyme can only detect free circulating
antibodies, and are incapable of detecting those bound up in immune complexes.
Investigational tests have been developed to free these sequestered antibodies
and render them measurable by the standard tests (Schutzer et al 1994).
- There is wide variability
between tests of commercial laboratories, and it is not unusual to have a
serum sample test positive in one lab and negative in another.
....
- Some people who appear to be in good health and have no Lyme related
symptoms may test positive.
- This may indicate past exposure to the Lyme
bacteria, with spontaneous recovery, or
- it may represent a dormant infection
which may activate at some future date and cause clinical disease.
This has
been well documented in the European literature.
The Western Blot is now commercially available for Lyme disease. Here
various sized Lyme antibodies are allowed to migrate on a strip of filter
paper. They separate into distinct bands, and serve as a 'fingerprint' for
Lyme disease. This technique is wrongly thought to be a 'confirmatory test'
for Lyme disease, which it is in AIDS. It may be useful to sort out false
positive tests and in cases where the antibody titer is 'borderline'. Since
its results depend on the presence of Lyme specific antibodies, the same
factors which can cause a negative test may cause a negative 'Western Blot'.
The Cell Mediated Immunity Test (CMI) or T-Lymphocyte Stimulation Test,
has also been used to make a laboratory diagnosis of Lyme disease. It
attempts to determine if one's immune system has 'memory' of exposure to Lyme
bacteria. It is currently done by Stony Brook University and several other
research laboratoies. It costs more that $300 to do and is very labor
intensive. It also has a high rate of false positive and false negative
results.
The most common errors made by physicians in interpreting these
previously mentioned tests are:
- A negative test excludes the diagnosis of
Lyme.
- A NEGATIVE TEST IN SOMEONE WHO PREVIOUSLY TESTED POSITIVE AND RECEIVED ANTIBIOTIC TREATMENT IMPLIES 'CURE'.
It must be stressed that these tests do not correlate with symptoms and activity of the Lyme bacteria once antibiotics are initiated.
- THERE IS NO
CURRENTLY AVAILABLE TEST FOR CURE.
- Physicians who monitor Lyme titers
(concentration of antibodies) during and after antibiotic therapy , and
pronounce their patients 'cured' when their test becomes negative, do not
understand what they are measuring and are wasting the patient's money and
doing them a disservice.
.....
The laboratory tests may be a useful adjunct in making the diagnosis, but negative results do not rule out the possibbility of the disease.
Ticked off Tract--June 1991
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