Recently one of my close
friends from my undergrad years was tested for Lyme Disease. As most of you
know, the causative agent for Lyme disease is Borrelia burgdorferi (more specifically Borrelia burgdorferi sensu strict). Luckily her test was negative,
but I came across an article that discussed the evolution of Borrelia serology testing which I found
interesting. This post will give a brief background on B. burgdorferi, and how testing as improved since it was discovered.
Borrelia burgdorferi is a spirochete, which is a spiral shaped bacterium. As stated earlier, it
responsible for Lyme disease. A distinctive feature of Lyme disease is a bull’s
eye rash. It is transmitted by ticks, which means you should listen to your
parents about being cautious when spending time in the woods. The organism is
difficult to grow in culture, and often it is diagnosed through serology tests.
Serology tests detect the antibodies made in response to the bacterium, not the
actual bacterium itself.
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Past Protocols
The first standard protocol
for testing this came about in 1994. The first cases of Lyme disease were in
mid-to-late 1970s. This is quite a large time gap where there was not a set
standard on testing. The first protocol was referred to as the “Two-Tier Test
Protocol” and followed the normal progression of the majority of tests today:
screening test followed by a confirmatory test. The screening test had high
sensitivity and detected IgG and IgM antibodies to B. burgodrferi. The portion of testing was usually an Enzyme-linked
immunosorbent assay (ELISA) or indirect fluorescent assay (IFA).
ELISA
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IFA
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If a patient tested positive
on the screening test, then a confirmatory test was performed. This test
consisted of separate IgG and IgM antibody immunoblots. This type of testing
runs the purified sample through a gel and adds B. burgdorferi antigen by blotting. If a precipitate or band forms,
the antibody is present to that antigen. This test has a high specificity. If
the patient receives a positive result, an official positive is reported. If
the patient receives a negative for either the screening or confirmatory test,
an official negative is reported.
Current Protocols
Fast forward in time to
2001, and the testing progression has not changed. The antigens used however
have improved from whole cell antigens to utilizing single, synthetic antigen:
26 mer synthetic peptide on invariable region 6 of Vmp-like sequence
lipoprotein. In 2003 scientists researched other antigens for testing:
recombinant V1sE1, synthetic C6, and synthetic pepC10. The names may sound like
jibberish to most, but these purified antigens allowed for a higher specificity
of 98% and higher sensitivity than the “Two-Tier Test Protocol” in patients
with acute Lyme disease. This resulted in more accurate diagnosis for patients.
The article concluded that testing with the combination of the rV1sE1 IgG (or
C6 IgG) in conjunction with pepC10 IgM is superior to testing the each antigen
alone. Using this information, they developed a multiplex immunoassay in
addition to an ELISA test that utilized both antigens in a solid phase. Now
testing is much easier to decipher and provides more accurate results.
Article reference:
Kopnitsky MJ. The evolution
of Borrelia serology tests. Medical Laboratory Observer. June 2013; 46.6: 24-25
