Potentially useful laboratory studies in suspected RA fall into three categories — markers of inflammation, hematologic variables, and immunologic variables — and include the following:
C-reactive protein level
Antinuclear antibody assay
Anti−cyclic citrullinated peptide and anti−mutated citrullinated vimentin assays
The CBC commonly demonstrates anemia of chronic disease and correlates with disease activity (present in 33%-60% of patients); it improves with successful therapy. Hypochromic anemia suggests blood loss, commonly from the gastrointestinal tract (associated with the use of nonsteroidal anti-inflammatory drugs). Anemia may also be related to disease-modifying antirheumatic drug (DMARD) therapy.
Routine viral screening by serologic testing does not significantly facilitate the diagnosis of RA in patients with early RA, nor is it helpful as a potential identifier of disease progression.
Assays for ACPA are now being clinically used for diagnosing RA. ACPA-positive and ACPA-negative RA may be two distinct disease subsets, with different underlying pathogeneses and risks of developing RA. Patients with ACPA-positive disease may have a more erosive condition than those who are ACPA-negative. Reassessment during the first year after onset does not appear to provide significant additional information.
RA often goes into remission during pregnancy. The presence of RF neither helps predict nor correlates with the outcome of arthritis during pregnancy. The ESR cannot be used to assess RA disease activity during pregnancy because pregnancy alters the normal values. The volume expansion that occurs during pregnancy can result in lower hematocrit values.
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Cite this: Herbert S. Diamond. Fast Five Quiz: Rheumatoid Arthritis Myths vs Facts - Medscape - Oct 25, 2021.