Rheumatoid Factor Test Flashcards
Rheumatoid factor
Antibody of IgM class which is directed against the Fc portion of IgG.
anti-CCP
Antibody against cyclic citrullinated proteins produced by the death of granulocytes and macrophages.
Give brief description of RA (definition, population, bone cell activity.)
Chronic, symmetric, erosive arthritis of peripheral joints.
Women 3x more likely
Excess adsorption of bone by osteoclasts
Describe the principle of the RF test.
Patient serum is mixed with latex reagent coated with human IgG. If RF is present, it will bind to IgG, causing visible agglutination of latex particles.
Explain the reason for titering a positive RF.
Allows us to estimate RF concentration and monitor treatment effectiveness.
5 reasons for a biological false positive RF.
- Elderly
- disseminated sarcoidosis
- syphilis
- essential hypertension
- hepatitis
Explain how RF can interfere with other IgM type antibody tests.
Can “mask” IgG, making it look like IgM. RF can be removed from serum before test is run.
Contrast clinical utility of RF and anti-CCP tests.
RF: only present in 70% adult patients, < 25% children.
anti-CCP: precedes onset of RA by several years; more specific than RF.
Combined, both tests have 98-100% specificity for RA.
List 2 treatments for RA.
Methotrexate - inhibits adenosine metabolism and t-cell activation
mAbs - target and neutralize TNF-a
List main tests used in monitoring treatment of RA. (4)
- RF
- CRP
- ESR
- Complement
IgM anti-IgG complexes with IgG cause…
complement activation
inflammation and tissue injury in synovial joints
sx in patients with RF > 1:320
- rheumatoid nodules
- destructive joint disease
- systemic complications (pleuritis, pericarditis, episcleritis, leg ulcers, vasculitis)
3rd Ab test for RA
- anti-nuclear antibodies are present in low titers in 40% of RA patients
