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HelpTest Code AC1Q Anti-C1q Antibodies, IgG, Serum
Specimen Required
Supplies: Sarstedt Aliquot Tube, 5 mL (T914)
Collection Container/Tube:
Preferred: Serum gel
Acceptable: Red top
Submission Container/Tube: Plastic vial
Specimen Volume: 0.5 mL
Collection Instructions: Centrifuge and aliquot serum into a plastic vial.
Secondary ID
621511Useful For
Evaluating patients with suspected anti-C1q vasculitis
Predicting renal involvement in patients with systemic lupus erythematosus
Detection of anti-C1q antibodies in serum
Method Name
Enzyme-Linked Immunosorbent Assay (ELISA)
Reporting Name
Anti-C1q Antibodies, IgG, SSpecimen Type
SerumSpecimen Minimum Volume
0.4 mL
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Serum | Refrigerated (preferred) | 21 days | |
| Frozen | 21 days |
Reject Due To
| Gross hemolysis | Reject |
| Gross lipemia | Reject |
| Gross icterus | Reject |
Clinical Information
Anti-C1q antibodies have been found to be prevalent in hypocomplementemic urticarial vasculitis syndrome (also referred to as anti-C1Q vasculitis) as well as in some patients with systemic lupus erythematosus (SLE)1,2. These antibodies occur more frequently in lupus nephritis, particularly during active disease. The main target clinical diseases include SLE and anti-C1Q vasculitis. Anti-C1q antibodies may also be seen in infectious diseases such as HIV and hepatitis C.
Reference Values
<20 U/mL (Negative)
20-39 U/mL (Weak Positive)
40-80 U/mL (Moderate Positive)
>80 U/mL (Strong Positive)
Interpretation
A positive result for Anti-C1q antibodies may support a diagnosis of anti-C1q vasculitis or renal involvement in patients with systemic lupus erythematosus in the appropriate clinical context.
A negative result indicates no detectable IgG antibodies to C1q and does not rule out a diagnosis.
Cautions
A positive result for anti-C1q antibodies indicates they are detectable above the assay’s lower limit of quantitation and does not unequivocally establish any diagnosis.
Clinical Reference
1. Dragon-Durey MA, Blanc C, Marinozzi MC, van Schaarenburg RA, Trouw LA. Autoantibodies against complement components and functional consequences. Mol Immunol. 2013;56(3):213-221
2. Defendi F, Thielens NM, Clavarino G, Cesbron JY, Dumestre-Perard C. The immunopathology of complement proteins and innate immunity in autoimmune disease. Clin Rev Allergy Immunol. 2020;58(2):229-251
3. Marzano AV, Maronese CA, Genovese G, et al. Urticarial vasculitis: Clinical and laboratory findings with a particular emphasis on differential diagnosis. J Allergy Clin Immunol. 2022;149(4):1137-1149
4. Hristova MH, Stoyanova VS. Autoantibodies against complement components in systemic lupus erythematosus - role in the pathogenesis and clinical manifestations. Lupus. 2017;26(14):1550-1555
5. Jachiet M, Flageul B, Deroux A, et al. The clinical spectrum and therapeutic management of hypocomplementemic urticarial vasculitis: data from a French nationwide study of fifty-seven patients. Arthritis Rheumatol. 2015;67(2):527-534
6. Jennette JC, Falk RJ, Bacon PA, et al. 2012 revised International Chapel Hill Consensus Conference Nomenclature of Vasculitides. Arthritis Rheum. 2013;65(1):1-11
7. Mehregan DR, Hall MJ, Gibson LE. Urticarial vasculitis: a histopathologic and clinical review of 72 cases. J Am Acad Dermatol. 1992;26(3):441–448
8. Damman J, Mooyaart AL, Seelen MAJ, van Doorn MBA. Dermal C4d deposition and neutrophil alignment along the dermal-epidermal junction as a diagnostic adjunct for hypocomplementemic urticarial vasculitis (Anti-C1q Vasculitis) and underlying systemic disease. Am J Dermatopathol. 2020;42(6):399-406
9. Marto N, Bertolaccini ML, Calabuig E, Hughes GR, Khamashta MA. Anti-C1q antibodies in nephritis: correlation between titres and renal disease activity and positive predictive value in systemic lupus erythematosus. Ann Rheum Dis. 2005;64(3):444-448
10. Shang X, Ren L, Sun G, et al. Anti-dsDNA, anti-nucleosome, anti-C1q, and anti-histone antibodies as markers of active lupus nephritis and systemic lupus erythematosus disease activity. Immun Inflamm Dis. 2021;9(2):407-418
Method Description
Testing for antibodies to C1q is accomplished using a laboratory-developed immunoassay.(Unpublished Mayo method)
Day(s) Performed
Wednesday
Report Available
2 to 8 daysSpecimen Retention Time
2 weeksPerforming Laboratory
Mayo Clinic Laboratories in Rochester
Test Classification
This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. It has not been cleared or approved by the US Food and Drug Administration.CPT Code Information
83520
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| AC1Q | Anti-C1q Antibodies, IgG, S | 44702-9 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| AC1Q | Anti-C1q Antibodies, IgG, S | 44702-9 |