C1qScreen™ Assay

Not all antibodies are the same.

Identify patients who may benefit from more aggressive immunosuppressive therapies by monitoring for C1q-binding donor-specific antibodies (DSAs).

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C1q Biomarker Utility in Post-Transplant Monitoring

C1q is a protein component of the complement system, which is part of the immune system. In kidney transplantation, C1q is used as a biomarker to help identify patients who are at greater risk of developing antibody-mediated rejection (AMR).

AMR is a type of rejection that can occur after kidney transplantation when the recipient's immune system produces antibodies against the transplanted kidney. These antibodies can cause damage to the transplanted kidney and lead to graft loss [1].

Studies have shown that the presence of C1q-binding DSAs is associated with an increased risk of developing AMR and graft loss. Therefore, monitoring for C1q-binding DSAs can help identify patients who may benefit from more aggressive immunosuppressive therapies or alternative treatment options [1,2,3].

In addition, some centers also use C1q as a part of their pre-transplant screening process to identify which potential kidney donors may be of higher risk for a particular individual [4]. Donors against whom the recipient has C1q-binding DSAs may be excluded from donating to that patient to reduce the risk of developing AMR post-transplant.

Use the C1qScreen assay to identify and screen complement-binding antibodies
in human sera.

Similar to the the One Lambda™ LABScreen™ Single Antigen Bead assay, our C1qScreen™ assay uses a bead-based assay where beads are coated with purified HLA molecules. Human serum and purified C1q molecules are then added. A specific antibody will bind to the HLA molecules, and C1q will bind to any complement-binding antibodies. The beads are then washed, and a secondary anti-C1q antibody labeled with a fluorescent tag is added. This secondary antibody will bind to any C1q-bound onto HLA antibodies present on the beads, and the level of fluorescence is measured. The amount of fluorescence is directly proportional to the level of complement-binding antibodies present in human serum.

The C1qScreen assay is a highly sensitive and specific test for detecting complement-binding antibodies.

C1qScreen Key Benefits

  • Identifies presence of complement binding antibodies
  • Based on Luminex® xMAP® technology
  • Now includes a positive control bead
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Disclaimer & References


C1qScreen (#C1Q) assay is CE-IVD: For In Vitro Diagnostic Use. (European Union Only). Product is CE-IVD marked but not 510(k)-cleared and not available for sale in the U.S. Availability of product in each country depends on local regulatory marketing authorization status.


  1. Loupy A, Lefaucheur C, Vernerey D, et al. Complement-binding anti-HLA antibodies and kidney-allograft survival. N Engl J Med 2013;369:1215-26.
  2. Wiebe C, Rush DN, Nevins TE, et al. Class II Eplet Mismatch Modulates Tacrolimus Trough Levels Required to Prevent Donor-Specific Antibody Development. Journal of the American Society of Nephrology. 28(11):3353-3362, November 2017.
  3. Einecke, G., Sis, B., Reeve, J., Mengel, M., Campbell, P.M., Hidalgo, L.G., Kaplan, B. and Halloran, P.F. (2009), Antibody-Mediated Microcirculation Injury Is the Major Cause of Late Kidney Transplant Failure. American Journal of Transplantation, 9: 2520-2531. https://doi.org/10.1111/j.1600-6143.2009.02799.x
  4. Tyan DB. Application, technical issues, and interpretation of C1q for graft outcome. Curr Opin Organ Transplant. 2017 Oct;22(5):505-510. doi: 10.1097/MOT.0000000000000454. PMID: 28723698; PMCID: PMC5662152.