C1q Antibody (IgG)

Test Code

34303

CPT Codes
83516

Preferred Specimen

0.5 mL serum collected in a red-top tube (no gel)

Minimum Volume

0.3 mL

Other Acceptable Specimens

Plasma collected in an EDTA (lavender-top) tube, or sodium heparin (green-top) tube

Transport Temperature

Room temperature

Specimen Stability

Room temperature: 7 days
Refrigerated: 14 days
Frozen: 42 days

Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)

Serum separator tube

Methodology
Enzyme Linked Immunosorbent Assay (ELISA)

FDA Status
This test was developed and its analytical performance characteristics have been determined by Quest Diagnostics. It has not been cleared or approved by the U.S. Food and Drug Administration. This assay has been validated pursuant to the CLIA regulations and is used for clinical purposes.

Setup Schedule

Set up: Sun, Thurs; Report available: 1-5 days

Reference Range

<26 RU/mL

Clinical Significance

This assay serves as a non-invasive aid for the diagnosis of active proliferative lupus nephritis (LN) and for monitoring disease activity. Autoantibodies to C1q (C1q Ab; IgG isotype) are detected in a number of autoimmune and infectious diseases but are best described in patients with systemic lupus erythematosus (SLE). Several studies suggest that C1q Ab plays a pathogenic role in the development of LN and that serum levels correlate with disease activity [1]. Moreover, C1q Ab results demonstrate fair sensitivity and specificity for active proliferative LN [2]. In addition, C1q Ab levels may begin to rise in advance of a renal flare and absence of C1q Ab suggests that a flare is unlikely [3].

References
1. Bock M, Heijnen I, Trendelenburg M. Anti-C1q antibodies as a follow-up marker in SLE patients. PLoS One. 2015;10(4):e0123572. doi:10.1371/journal.pone.0123572
2. Yin Y, Wu X, Shan G, et al. Diagnostic value of serum anti-C1q antibodies in patients with lupus nephritis: a meta-analysis. Lupus. 2012;21(10):1088-1097. doi:10.1177/0961203312451202
3. Fatemi A, Samadi G, Sayedbonakdar Z, et al. Anti-C1q antibody in patients with lupus nephritic flare: 18-month follow-up and a nested case-control study. Mod Rheumatol. 2016;26(2):233-239. doi:10.3109/14397595.2015.1074649

The CPT Codes provided in this document are based on AMA guidelines and are for informational purposes only. CPT coding is the sole responsibility of the billing party. Please direct any questions regarding coding to the payor being billed. Any Profile/panel component may be ordered separately. Reflex tests are performed at an additional charge.