What laboratory test is often used to support a diagnosis of rheumatoid arthritis?

The anti-cyclic citrullinated peptide antibody (anti-CCP antibody) is a specific laboratory test that is particularly important in supporting the diagnosis of rheumatoid arthritis (RA). This antibody is highly associated with the disease and can often be detected in patients before clinical symptoms arise, making it a valuable tool in early diagnosis. The presence of anti-CCP antibodies is not only specific for rheumatoid arthritis but also correlates with the severity of the disease, providing additional insights into the prognosis.

In contrast, the complete blood count primarily assesses general health and can identify anemia or inflammation but is not specific for rheumatoid arthritis. Liver function tests evaluate liver health and are unrelated to the diagnosis of RA. Similarly, thyroid function tests are used to assess thyroid health and do not provide information concerning rheumatoid arthritis. Thus, among the options, anti-CCP antibodies play a critical role in the diagnostic process for rheumatoid arthritis.