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- Lyme disease is diagnosed by a combination of features.
The most important starting point, of course,
is what the patient's experiencing,
the symptoms of Lyme disease.
Unfortunately, the symptoms such as fatigue
and fever and achiness are common symptoms
in many illnesses.
So, by themselves, the symptoms cannot be used
to diagnose Lyme disease.
A little more reliable than symptoms
are what are called signs of the disease.
These are more reliable because they're more unique
to Lyme disease.
For instance, the rash, that round, red lesion
is fairly unique.
And it's fairly specific for Lyme disease.
So, sometimes we can make a diagnosis based
on the rash if it's present.
But the rash isn't always present.
If we see the rash and discover it,
then that can actually be diagnostic by itself.
In the later stages of Lyme disease
there are also signs that you can see.
Facial palsy in the second stage,
swollen knees in the third stage.
Those signs are somewhat specific for Lyme disease
but not absolutely.
There are other causes of Bell's palsy.
There's other causes of swollen knees.
So, in those later stages that second and third stage,
the diagnosis needs to be confirmed by a blood test
which is called a serology blood test.
This blood test measures the antibodies
that are formed by your own immune system
in response to the Lyme disease bacterial infection.
So, these antibodies are measured using
what's called an ELISA test.
If the ELISA test is positive, it's confirmed
by what's called a western blot test.
So, this ELISA/western blot combination
is called the two-tier testing strategy.
It is helpful for second and third stages of Lyme disease
but not helpful for first stage Lyme disease.
The reason for that is because it's an antibody test.
Antibodies take weeks to develop.
So, at the initial presentation of Lyme disease
in the first stage, those antibody tests
may be falsely negative because the immune system
hasn't had enough time to produce the antibodies.
Because of that, if the physician is still suspicious
of Lyme disease and they can't make the diagnosis
by the rash, then the antibody test in that first stage
can be done but it should be repeated
three to four weeks later to make sure
that we haven't missed a diagnosis
with a false negative test in the first few weeks.
What we would like to see in the future
are tests that directly measure the infection.
These would be tests like a culture or a PCR test
or an antigen detection test.
Those are the kind of tests that we rely on
in infectious diseases for other infections
like HIV or hepatitis C or strep.
There, we're actually looking at a direct test
that measures the presence of the bacteria.
Those are obviously much more reliable
than a test that's looking for indirect measurement
of antibodies which don't represent the actual infection.
The antibodies represent the immune response
to the infection.
So, very important difference between direct tests
which are not generally available for Lyme disease
and a serology test which measure immunologic recognition
and immunologic memory.
At the Johns Hopkins Lyme Disease Research Center,
we're actually looking at new ways to develop
direct diagnostics tests such as PCR tests
that would directly identify
the bacteria Borrelia burgdorferi
and wouldn't rely on the older serologic tests.
Since Lyme disease is a tick-borne infection,
the seasonality of the disease is linked tightly
to the behavior of ticks.
Nymph stage or adolescent ticks
feed in the late spring and early summer.
They transit most of Lyme disease
because they're very small, about the size of a poppy seed.
Very difficult for patients to see or feel.
Because of this Nymph stage tick feeding pattern,
most of Lyme disease is actually transmitted
in the late spring and early summer.
Probably 80-plus percent of the cases are transmitted.
So, we know that there's a high seasonality
and that May, June, and July are the big risk months
for acquiring first stage Lyme disease.
Adult stage ticks feed in the fall and winter
so there is some transmission of Lyme disease
in the fall and winter and throughout the year.
But, that's a small percentage of cases.
The vast majority are transmitted in May, June,
and July and early August.
That's the reason that we have to be especially vigilant
for unusual symptoms in the early summer months.
Especially that early summer flu-like illness
that is not typical, that lacks typical viral symptoms
like runny nose or prominent cough
or prominent diarrhea.
In the absence of those typical viral symptoms,
that summer viral-like illness may actually be Lyme disease.
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