Arthritis & Rheumatism, Volume 63,
November 2011 Abstract Supplement

Abstracts of the American College of
Rheumatology/Association of Rheumatology Health Professionals
Annual Scientific Meeting
Chicago, Illinois November 4-9, 2011.

Anti-C1q Antibody in Systemic Lupus Erythematosus.

Orbai1,  Ana-Maria, Sturfelt2,  Gunnar K., Nived3,  Ola, Fang1,  Hong, Alarcon4,  Graciela S., Gordon5,  Caroline, Merrill6,  Joan T.

Johns Hopkins University School of Medicine, Baltimore, MD
Cedars-Sinai/UCLA, Los Angeles, CA
Northwestern University Feinberg School of Medicine, Chicago, IL
Hanyang University Hospital for Rheumatic Diseases, Clinical Research Center for Rheumatoid Arthritis (CRCRA), Seoul, South Korea
Dalhousie University, Halifax, NS
University Health Network/Mount Sinai Hospital, Toronto, ON
Research Institute of the McGill Univ. Health, Montreal, QC
Feinstein Institute for Medical Research, Manhasset, NY
Allegheny Singer Research Institute, Pittsburgh, PA
Toronto Western Hospital and University of Toronto, Toronto, ON
Toronto Western Research Institute, University of Toronto, University Health Network, Toronto, ON
University Hospital Lund, Lund, Sweden
UCSD School of Medicine, La Jolla, CA
North Dallas Dermatology Assoc, Dallas, TX
University of Maryland, Baltimore, MD
University Hospital, Lund, Sweden
University of Alabama at Birmingham, Birmingham, AL
University of Birmingham, Birmingham, United Kingdom
Oklahoma Medical Research Foundation, Oklahoma City, OK
Toronto Western Hospital, Toronto, ON
A, Manchester, United Kingdom
University College London, London WC1E 6JF, United Kingdom


Anti-C1q antibody has been associated with SLE and SLE nephritis in single-center studies. We studied anti-C1q antibody specificity for SLE (vs. rheumatic disease controls) and its association with SLE manifestations in an international multi-center study.


Information and blood samples were obtained from 308 patients with SLE and 389 patients with other rheumatologic diseases from 25 clinical sites (84% female, 68% Caucasian, 17% African descent, 8% Asian, 7% other). Anti-C1q antibody was measured by an ELISA using IgG antibodies against the collagen-like region of C1q (anti-C1qCLR). P-values were calculated based on the chi-square test (SAS Institute, Cary, NC, USA).


The prevalence of anti-C1q antibody was 28% (86/308) in SLE patients and 13% (49/389) in controls (P-value <.0001), odds ratio 2.7 (95% CI: 1.8, 4.0). By the submitting diagnosis, the frequency of anti-C1q antibody in controls was: 26% in scleroderma, 19% in rheumatoid arthritis, 15% in undifferentiated connective tissue disease, 15% in chronic cutaneous lupus, 14% in Sjögren syndrome, 8% in fibromyalgia, 7% in antiphospholipid antibody syndrome, 6% in dermatomyositis, and 5% in vasculitis.

Table 1. Association between Demographic Characteristics and Anti-C1q Antibody in SLE: Percentage of Patients with Anti-C1q Antibody, by Demographic Variables

  Percentage for Anti-C1qP-value
EthnicityAfrican Descent21.70.15

Table 2. Association between ACR Criteria and Anti-C1q Antibody in SLE: Percentage of Patients with Various Clinical Conditions, by Anti-C1q Status

 Positive Anti-C1q (%)Negative Anti-C1q (%)P-valueOdds Ratio (95% CI)Adjusted P-value for Age
Malar Rash47.746.90.900.9 (0.5, 1.5)0.69
Discoid Rash19.819.40.941.1 (0.6, 2.1)0.71
Photosensitivity53.553.20.961.0 (0.6, 1.7)1.00
Oral Ulcers38.446.40.200.7 (0.4, 1.1)0.14
Arthritis64.065.80.760.9 (0.5, 1.5)0.70
Serositis37.234.70.681.1 (0.6, 1.8)0.84
Pleurisy31.428.40.601.1 (0.6, 1.9)0.74
Pericarditis14.012.20.671.2 (0.6, 2.5)0.66
Proteinuria50.022.5<.00013.0 (1.7, 5.1)<.0001
Urinary casts18.67.20.00332.6 (1.2, 5.4)0.015
Seizure5.84.10.511.2 (0.4, 3.8)0.72
Psychosis3.50.50.0359.5 (0.9, 98.5)0.059
Hematologic64.058.10.351.2 (0.7, 2.0)0.49
Leukopenia40.735.10.361.2 (0.7, 2.0)0.48
Lymphopenia38.436.50.761.1 (0.7, 1.8)0.73
Thrombocytopenia15.112.20.491.1 (0.5, 2.2)0.86
Anti-dsDNA77.947.8<.00013.4 (1.9, 6.1)<.0001
Anti-Smith33.714.40.00012.8 (1.5, 5.0)0.0007
Antiphospholipid57.054.50.701.1 (0.7, 1.8)0.70

Table 3. Association with Renal Lupus: Percentage of Patients with SLE Serologies among those with and without Lupus Nephritis

VariableRenal Lupus (%)No Renal Lupus (%)P-ValueOdds Ratio (95% CI)Adjusted P-value for Age and Race
Anti-C1q45.519.3<.00013.2 (1.8, 5.6)<.0001
Anti-dsDNA80.244.4<.00014.7 (2.5, 8.6)<.0001
Anti-Smith29.715.00.00231.9 (1.1, 3.6)0.03
Low complement78.250.2<.00012.8 (1.5, 4.9)0.0006


Anti-C1q antibody was found in 28% of SLE patients, although it was also found in other rheumatologic diseases. It was more common in Asians than in Caucasians or patients of African descent. In terms of SLE manifestations, it was associated with renal lupus, anti-dsDNA antibody, low complement and anti-Smith antibody. Anti-C1q antibody was more highly associated with renal lupus than anti-Smith antibody was. Although complexities of the assay have limited its introduction as a routine test, these data clearly point to its utility in SLE, especially in lupus nephritis.

To cite this abstract, please use the following information:
Orbai, Ana-Maria, Sturfelt, Gunnar K., Nived, Ola, Fang, Hong, Alarcon, Graciela S., Gordon, Caroline, et al; Anti-C1q Antibody in Systemic Lupus Erythematosus. [abstract]. Arthritis Rheum 2011;63 Suppl 10 :1375

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