RF, IgA by EIA

Laboratory assay overview

This panel can be helpful in the diagnosis of systemic rheumatic disorders and other autoimmune diseases. Although the test for antinuclear antibodies (ANA) is strongly associated with systemic lupus erythematosus (SLE), the laboratory evaluation for individuals with clinical suspicion of a variety of autoimmune diseases often begins with an ANA screen. This panel simultaneously tests for ANA (using immunofluorescence) as well as the important specific autoantibodies associated with a positive ANA. It also includes testing for complement proteins, rheumatoid arthritis, Sjogren's syndrome, systemic sclerosis, polymyositis, anti-phospholipid antibody syndrome, and autoimmune thyroid disease.

Laboratory assay overview

This assay may be useful in supporting or ruling out a diagnosis of rheumatoid arthritis.

Quest Diagnostics population reference ranges

Quest Diagnostics calculates these statistical intervals for this specific assay and demographic group, not as universal optimal targets.

Laboratory assay overview

The concentration of RF tends to be highest when the disease peaks and tends to decrease during prolonged remission. RF IgM is found in 1 to 4% of the general population. RF is present in 75% of adult RA patients with the highest incidence of RF occurring in persons over 65 years of age. Increased RF levels may also accompany a variety of acute immune responses, particularly viral infections and a number of liver diseases (infectious mononucleosis, tuberculosis, leprosy, various parasitic diseases, liver disease, sarcoidosis, and systemic lupus erythematosus). In addition to RF IgM, raised levels of RF IgA and IgG have been reported in patients with RA. Studies from as early as 1984 suggest that the detection of RF IgA in early disease indicates poor prognosis and justifies a more aggressive course of treatment. Recently, it has become apparent that the specificity and predictive value of the RF test is substantially increased by the detection of all three RF isotypes.

Quest Diagnostics population reference ranges

Quest Diagnostics calculates these statistical intervals for this specific assay and demographic group, not as universal optimal targets.

Laboratory assay overview

In conjunction with clinical findings and other laboratory tests, the presence of rheumatoid factor (RF) can be used to aid in the diagnosis of rheumatoid arthritis.

Quest Diagnostics population reference ranges

Quest Diagnostics calculates these statistical intervals for this specific assay and demographic group, not as universal optimal targets.

Laboratory assay overview

EIA methods have the added advantage of being able to simultaneously detect RF of IgG and IgA subclasses in addition to RF IgM and are not susceptible to prozone. It has become apparent that the specificity and predictive value of the RF test is substantially increased by the detection of all three RF isotypes.

Laboratory assay overview

EIA methods have the added advantage of being able to simultaneously detect RF of IgG and IgA subclasses in addition to RF IgM and are not susceptible to prozone. It has become apparent that the specificity and predictive value of the RF test is substantially increased by the detection of all three RF isotypes.