New blood test could predict arthritis risk early

Marker can indicate likelihood of suffering from
rheumatoid arthritis even 16 years before condition takes effect

University of
OxfordSummary:Testing for antibodies that target citrullinated tenascin-C
(cTNC) could diagnose rheumatoid arthritis in around 50 percent of cases,
including some cases not identified by current best tests. It also has a very
low rate of false positives — 98 percent accurate at ruling out rheumatoid
arthritis.

Scientists have found a marker that can indicate your
likelihood of suffering from rheumatoid arthritis (RA) even sixteen years
before the condition takes effect. A team from the Kennedy Institute of
Rheumatology at Oxford University found that a blood test that looks for
antibodies that recognize the protein tenascin-C could reliably show those who
will contract the condition.

When inflammation occurs in the body, some proteins are
altered in a process called citrullination. These altered forms can prompt an
immune response from the body, which can see it turning antibodies on itself —
causing rheumatoid arthritis. For that reason, tests that spot antibodies to
citrullinated proteins are already used to diagnose the disease. While tests
for individual proteins usually have a relatively low diagnostic sensitivity, a
more general test called CCP, that detects synthetic citrullinated peptides,
identifies a lot more RA cases.

Lead researcher Dr Anja Schwenzer said: ‘We knew that
tenascin-C is found at high levels in the joints of people with RA. We decided
to see if it could be citrullinated and, if so, whether it was a target for the
autoantibodies that attack the body in RA. That might also indicate whether it
could be used in tests to indicate the disease.

‘When we looked at results from more than 2000 patients
we found that testing for antibodies that target citrullinated tenascin-C
(cTNC) could diagnose RA in around 50% of cases, including some cases not
identified by CCP. It also has a very low rate of false positives — it is 98%
accurate at ruling out RA.’

The Kennedy Institute’s Professor Kim Midwood said: ‘What
is particularly exciting is that when we looked at samples taken from people
before their arthritis began, we could see these antibodies to cTNC up to 16
years before the disease occurred — on average the antibodies could be found
seven years before the disease appeared.

‘This discovery therefore gives us an additional test
that can be used to increase the accuracy of the CCP assay and that can predict
RA, enabling us to monitor people and spot the disease early. This early
detection is key because early treatment is more effective.’

Stephen Simpson, Research Director, for Arthritis
Research UK said: ‘When it comes to rheumatoid arthritis, early diagnosis is
key with research showing that there is often a narrow ‘window of opportunity’
following the onset of symptoms for effective diagnosis and control of disease
through treatment. Furthermore, current tests for rheumatoid arthritis are
limited in their ability to diagnose disease in different patients. This latest
research provides the basis of tests that could improve diagnosis and,
importantly, detect disease at a very early stage, with the promise even that
people at risk of developing rheumatoid arthritis can be followed before the
disease begins. This could have great potential to help patients with
rheumatoid arthritis get the right treatment early to keep this painful and
debilitating condition under control.’

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