antibody test, blood
ANTI-CYCLIC CITRULLINATED PEPTIDE ANTIBODIES:
Another MARKER FOR RHEUMATOID ARTHRITIS
"Citrullinated peptide" is a synthetic peptide antigen used by manufacturors as the target antigen for the detection
of patient autoantibodies to citrullinated antigens2 (the RF serological test is generally considered to be more
sensitive at 75-85% but less specific at 60-65%3). Anti-CCP
was shown to be highly specific for seropositive rheumatoid
arthritis (98%) utilizing a simple ELISA
assay1. Many rheumatologists are now (2006) testing for both anti-CCP & RF
in an attempt to make an earlier specific diagnosis in cases of undifferentiated arthritis3. Furthermore, 35% of seronegative rheumatoid arthritis patients
were anti-CCP positive. In addition, a recent study demonstrated
anti-CCP antibodies in 70% of patients in the early stages of rheumatoid
Older general tests are ESR and CRP. Anti-perinuclear antibody, anti-keratin antibody and
anti-filaggrin antibody have also been shown to be highly specific
for rheumatoid arthritis, but there are no commercial assays available
for these tests for a variety of reasons. Recently, the above antibodies
have been shown to be directed against citrullinated substrates.
Because of its high
specificity, the anti-CCP test should be extremely useful in differentiating
rheumatoid arthritis (RA) from other diseases that can be difficult
to distinguish from RA because these diseases may have both (1) arthritis
and (2) rheumatoid factor positivity as features of their diseases
(SLE, Sjogren's syndrome, hepatitis C, parvoviral arthropathy,
sarcoidosis, seronegative spondyloarthropathy and others).
"RDL, Inc. has recently conducted an in-house analysis on patients'
sera stored at 70 degrees C in our facility utilizing a commercial
assay for anti-CCP. Our results demonstrate 98% specificity for anti-CCP
in RA and a sensitivity of 62% in agreement with the results reported
in the literature. We detected anti-CCP in only 2.5% of SLE and 5%
of parvoviral arthritis. We failed to detect anti-CCP in all other
disease categories...recognizing that small numbers of patients'
sera were available for testing, i.e., sarcoid arthropathy and hepatitis
C arthropathy. It therefore appears likely that the anti-CCP assay
will prove to be extremely valuable in the diagnosis of rheumatoid
arthritis, in the differential diagnosis of rheumatoid factor-positive
disorders potentially confused with RA, in confirming a diagnosis
of RA in seronegative polyarthritis and in the diagnosis of RA in
early synovitis patients1."
Potential false positives in some
- Parvoviral Arthropathy, 5%of cases
- SLE, 2.5% of cases
- Early Synovitis
- Hepatitis C
- Seronegative Inflammatory Arthropathy
- Polymyalgia Rheumatica
- Spondyloarthropathy 0/19
- Ankylosing Spondylitis
- Psoriatic Arthritis
- Reiter's Syndrome
- Inflammatory Bowel Disease with Arthritis
- Undifferentiated Spondyloarthropathy
- Remitting Seronegative Symmetrical Synovitis with Pitting Edema
- Schellekens GA, Visser H Ben, de Jong DAW: "The
Diagnostic Properties of RA Antibodies Recognizing a Cyclic..." Rheumatism, 2000;43:144-163. (see RDL, Inc. website, educational area).
- Carolyn Beck, EdD., 2006 CME flyer for UTHSC @ SA audio-conference CMEs.
- Ellen Sullivan, "Rheumatoid Arthritis: Test for Anti-CCP Antibodies Joining RF Test as Key Diagnostic Tools", LABMEDICINE (ASCP) 37(1):17-19, Jan. 2006.
|(posted 24 August 2002; latest addition 5 August 2006)
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