Anti-C1q autoantibodies as markers of renal involvement in childhood-onset systemic lupus erythematosus.
Childhood-onset systemic lupus erythematosus (cSLE) is rare, and considered more severe than its adult-onset counterpart. Lupus nephritis (LN) occurs more frequently in children, accounting for higher long-term morbidity and mortality compared with adults. Thus, reliable biological markers are needed to predict disease course. This study aimed to investigate the capacity of anti-C1q autoantibodies (Abs) to predict renal flare and global disease activity in cSLE patients, and association with disease activity and kidney involvement.



Twenty-eight patients with cSLE including 19 patients (68%) with a history of LN were included retrospectively. Anti-C1q Abs were analysed by ELISA at renal flare-up or in the quiescent phase of disease and compared with Farr dsDNA assay.



Thirty-one flares occurred during follow-up: anti-C1q Abs were positive in 26 (84%), strongly associated with active disease status (p < 0.0001), and correlated with global disease activity score (p < 0.0001) and anti-dsDNA Abs presence (p < 0.0001). The specificity of anti-C1q Abs was higher than anti-dsDNA (73% vs 19%) in discriminating LN patients, whereas the receiver operating characteristic curves were not statistically different (0.83 ± 0.06 vs 0.78 ± 0.08 respectively), similar to C3 dosage. The presence of anti-C1q Abs at diagnosis was not predictive for global or renal flare. Introduction of a modified SLEDAI score excluding dsDNA Abs, demonstrated a stronger correlation of anti-C1q Abs titres with SLEDAI score in comparison with the Farr test.



Anti-C1q Abs seem very specific to flares, including LN in children, and their role in daily practice compared with the Farr dsDNA assay needs to be defined.
Department of Pathology, Hôpital Femme-Mère-Enfant, Hospices Civils de Lyon, 59 boulevard Pinel, 69500, Bron, France. cecile.picard@chu-lyon.fr.|Université Claude Bernard Lyon 1, Lyon, France. cecile.picard@chu-lyon.fr.
Cécile
0000-0001-9284-4531
C
Picard
Université Claude Bernard Lyon 1, Lyon, France.|UMR 5558, Laboratoire de Biométrie et Biologie Evolutive, CNRS, Claude Bernard University Lyon 1, University of Lyon, Lyon, France.|Department of Internal and Vascular Medicine, Centre Hospitalier Lyon-Sud, Pierre-Benite, CHU de Lyon, Lyon, France.
Jean-Christophe
JC
Lega
Université Claude Bernard Lyon 1, Lyon, France.|Department of Pediatric Nephrology, Rheumatology and Dermatology, Hospices civils de Lyon, Lyon, France.
Bruno
B
Ranchin
Université Claude Bernard Lyon 1, Lyon, France.|Department of Pediatric Nephrology, Rheumatology and Dermatology, Hospices civils de Lyon, Lyon, France.
Pierre
P
Cochat
Université Claude Bernard Lyon 1, Lyon, France.|Department of Pediatric Nephrology, Rheumatology and Dermatology, Hospices civils de Lyon, Lyon, France.
Natalia
N
Cabrera
Université Claude Bernard Lyon 1, Lyon, France.|Department of Immunology, Centre Hospitalier Lyon-Sud, Pierre-Benite, CHU de Lyon, Lyon, France.
Nicole
N
Fabien
Université Claude Bernard Lyon 1, Lyon, France.|Department of Pediatric Nephrology, Rheumatology and Dermatology, Hospices civils de Lyon, Lyon, France.
Alexandre
A
Belot
D000293:Adolescent; D017668:Age of Onset; D001323:Autoantibodies / Q000097:blood* / Q000276:immunology; D015415:Biomarkers / Q000097:blood; D002648:Child; D002675:Child, Preschool; D015922:Complement C1q / Q000276:immunology*; D004247:DNA / Q000276:immunology; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D007668:Kidney / Q000276:immunology; D008181:Lupus Nephritis / Q000097:blood / Q000175:diagnosis* / Q000276:immunology; D008297:Male; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D000067251:Symptom Flare Up
D001323:Autoantibodies; D015415:Biomarkers; D015922:Complement C1q; D004247:DNA
Anti-C1q antibody; Biomarker; Childhood-onset systemic lupus erythematosus; Lupus nephritis; Pediatrics; SLEDAI