title: Autoantibodies against C1q as a Diagnostic Measure of Lupus Nephritis: Systematic Review and Meta-analysis.
abstract: OBJECTIVE
  To evaluate the diagnostic accuracy of C1q autoantibodies in identifying lupus nephritis (LN) in patients with systemic lupus erythematosus (SLE).
  
  
  METHODS
  Citation indexes were searched and 370 articles published from 1977 to 2013 were evaluated. The 31 selected studies included in the meta-analysis were cross-sectional in design. Among the 31 studies, 28 compared anti-C1q antibodies in 2769 SLE patients with (n=1442) and without a history of LN (n=1327). Nine studies examined anti-C1q in 517 SLE patients with active (n=249) and inactive LN (n=268). Hierarchical summary receiver operating characteristic (HSROC) random effects models were fitted to pool estimates of accuracy across the studies.
  
  
  RESULTS
  Anti-C1q antibodies discriminated between patients with and without a history of LN, with a median specificity of 73.5%. The HSROC model estimated the corresponding sensitivity to be 70.4%. A hypothetical patient with a 55% prior probability of having a history of LN as opposed to no history (the median prevalence across 28 eligible studies) would have a post-test probability of 76.4% following a positive test result (positive predictive value) or 33.0% following a negative test result (negative predictive value). For discriminating active from inactive LN the median specificity of anti-C1q antibodies was 80%, with a corresponding estimated sensitivity value 75.7% based on the HSROC model. A hypothetical patient with a 56% prior probability of active as opposed to inactive LN (the median prevalence across the 9 eligible studies) would have a post-test probability of 82.8% following a positive test result or 27.9% following a negative test result.
  
  
  CONCLUSIONS
  Although C1q antibodies are associated with lupus nephritis the post-test probabilities are not sufficiently convincing to provide reasonable certainty of the presence or absence of history of disease/active disease.
authors: Institute of Biomedical and Clinical Sciences, University of Exeter Medical School, University of Exeter, Exeter, UK.
authors: Paul
authors: P
authors: Eggleton
authors: NIHR CLAHRC South West Peninsula (PenCLAHRC),University of Exeter Medical School, University of Exeter, Exeter, UK.
authors: Obioha C
authors: OC
authors: Ukoumunne
authors: Institute of Biomedical and Clinical Sciences, University of Exeter Medical School, University of Exeter, Exeter, UK.
authors: Isabel
authors: I
authors: Cottrell
authors: Institute of Biomedical and Clinical Sciences, University of Exeter Medical School, University of Exeter, Exeter, UK.
authors: Asma
authors: A
authors: Khan
authors: Institute of Biomedical and Clinical Sciences, University of Exeter Medical School, University of Exeter, Exeter, UK.
authors: Sidra
authors: S
authors: Maqsood
authors: Institute of Biomedical and Clinical Sciences, University of Exeter Medical School, University of Exeter, Exeter, UK.
authors: Jemma
authors: J
authors: Thornes
authors: Institute of Biomedical and Clinical Sciences, University of Exeter Medical School, University of Exeter, Exeter, UK.
authors: Elizabeth
authors: E
authors: Perry
authors: Centre for Rheumatology, Department of Medicine University College London, UK.
authors: David
authors: D
authors: Isenberg
keywords: Autoantibody; Biopsy; Diagnosis; Enzyme-linked immunosorbent assay (ELISA); First component of complement (C1q); Hierarchical summary receiver operating characteristic (HSROC); Systemic lupus erythematosus (SLE)