Complement Component C3c and C4c

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 panel can be helpful in the diagnosis and management of systemic lupus erythematosus (SLE). The panel simultaneously tests for antinuclear antibodies (ANAs) with an immunofluorescence assay (IFA), performed on human epithelial type 2 (HEp-2) cells, as well as 6 specific autoantibodies associated with SLE and 3 biomarkers associated with disease activity. For specimens with positive ANA IFA results, reflex testing for ANA titer and pattern is performed. The ANA testing has high sensitivity (97%) for SLE but limited specificity (34%) [1]. Anti-dsDNA and anti-Sm antibodies are less sensitive but more specific; tests for both antibodies are included in classification criteria for SLE [2]. Anti-chromatin antibodies have relatively high sensitivity and specificity. Although antibodies to SSA and SSB may also be seen in Sjogren Syndrome and anti-RNP is a marker of mixed connective tissue disease, these antibodies are also frequently present in SLE and may be helpful. The results of this test should be interpreted in the context of pertinent clinical and family history and physical examination findings. References 1. Petri M, et al. Arthritis Rheum. 2012;64(8):2677-2686. 2. Aringer M, et al. Ann Rheum Dis. 2019;78(9):1151-1159.

Laboratory assay overview

This panel can be helpful in the diagnosis of systemic lupus erythematosus (SLE) and several other autoimmune diseases, including mixed connective tissue disease, Sjogren syndrome, systemic sclerosis, and autoimmune thyroid disease. The panel simultaneously tests for antinuclear antibodies (ANAs) with an immunofluorescence assay (IFA), performed on human epithelial type 2 (HEp-2) cells, and 11 biomarkers associated with these conditions. For specimens with positive ANA IFA results, reflex testing for ANA titer and pattern is performed. The ANA testing has high sensitivity (97%) for SLE but limited specificity (34%) [1]. Thus, a positive ANA test does not exclude other autoimmune diseases with similar clinical features [2]. Testing for specific antibodies in a panel may expedite the evaluation of SLE but is generally not recommended [3]. The results of this test should be interpreted in the context of pertinent clinical and family history and physical examination findings. References 1. Petri M, et al. Arthritis Rheum. 2012;64(8):2677-2686. 2. Kavanaugh A, et al. Arch Pathol Lab Med. 2000;124(1):71-81. 3. Yazdany J, et al. Arthritis Care Res (Hoboken). 2013;65(3):329-339.