Serum anti-lipocalin 2 IgG is a novel biomarker in the diagnosis of systemic lupus erythematosus.
BACKGROUND
Previous work suggests that lipocalin 2 is involved in the pathogenesis of systemic lupus erythematosus (SLE) and that this novel antigen could serve as a high-quality renal biomarker of acute kidney injury in SLE. However, serum lipocalin 2 antibody levels remain unclear. We have therefore undertaken this study to assess the level of serum IgG antibody against lipocalin 2 in different disease states and to evaluate the diagnostic value of this potential biomarker in SLE.


METHODS
Serum levels of anti-lipocalin IgG antibodies were measured by ELISA in 103 SLE patients, 93 rheumatoid arthritis (RA) patients, 29 primary Sjögren's syndrome (pSS) patients, 13 systemic sclerosis (SSc) patients, and 91 healthy controls. Diagnostic properties of anti-lipocalin IgG were determined by receiver-operating characteristic (ROC) curve analysis.


RESULTS
The level of serum anti-lipocalin IgG in patients with SLE was significantly higher than in patients with RA, pSS, SSc, or healthy controls (p < 0.05), effectively distinguishing SLE from other conditions with high sensitivity and specificity (49.5% and 90.7%, respectively). In ROC curve analysis, the area under the curve (AUC) is 0.783, with a 95% confidence interval (CI) extending from 0.729 to 0.839. Anti-lipocalin antibodies were present in 48.1% of anti-Sm-negative SLE patients, and also occurred in SLE patients lacking anti-dsDNA (52%) or anti-nucleosome antibodies (46.3%) antibodies. Finally, SLE patients with positive anti-lipocalin IgG possessed higher levels of IgA and CRP than the negative group (p < 0.05), clearly demonstrating a positive correlation between anti-lipocalin IgG and these laboratory parameters.


CONCLUSIONS
Anti-lipocalin 2 IgG is a promising biomarker for the diagnosis of SLE, particularly when obtained in conjunction with anti-Sm, anti-dsDNA, and anti-nucleosome antibody levels.
Department of Rheumatology & Immunology, Peking University People's Hospital, Beijing, China.
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YN
Li
Department of Rheumatology & Immunology, Peking University People's Hospital, Beijing, China.
F L
FL
Hu
Department of Rheumatology & Immunology, Peking University People's Hospital, Beijing, China.
Y J
YJ
Dai
Department of Rheumatology & Immunology, Peking University People's Hospital, Beijing, China.
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R
Li
Department of Rheumatology & Immunology, Peking University People's Hospital, Beijing, China.
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Ma
Department of Rheumatology & Immunology, Peking University People's Hospital, Beijing, China.
Y
Y
Du
Department of Rheumatology & Immunology, Peking University People's Hospital, Beijing, China.
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M
Feng
Department of Rheumatology & Immunology, Peking University People's Hospital, Beijing, China.
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Y
Jia
Clinical Epidemiology & Biostatistics, Peking University People's Hospital, Beijing, China.
C F
CF
Zhang
Department of Rheumatology & Immunology, Peking University People's Hospital, Beijing, China.
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L
Zhu
Department of Medicine, Division of Rheumatology, University of Miami Miller School of Medicine, USA DAscherman@med.miami.edu.
D P
DP
Ascherman
Department of Rheumatology & Immunology, Peking University People's Hospital, Beijing, China DAscherman@med.miami.edu.
Z G
ZG
Li
D000209:Acute-Phase Proteins / Q000276:immunology*; D000293:Adolescent; D000328:Adult; D000368:Aged; D001323:Autoantibodies / Q000097:blood*; D015415:Biomarkers / Q000097:blood; D005260:Female; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood*; D000071068:Lipocalin-2; D054834:Lipocalins / Q000276:immunology*; D008180:Lupus Erythematosus, Systemic / Q000097:blood* / Q000175:diagnosis*; D008297:Male; D008875:Middle Aged; D011518:Proto-Oncogene Proteins / Q000276:immunology*; D055815:Young Adult
D000209:Acute-Phase Proteins; D001323:Autoantibodies; D015415:Biomarkers; D007074:Immunoglobulin G; C489506:LCN2 protein, human; D000071068:Lipocalin-2; D054834:Lipocalins; D011518:Proto-Oncogene Proteins
Lipocalin 2; ROC curve; anti-lipocalin IgG; neutrophil gelatinasea-associated lipocalin (NGAL); systemic lupus erythematosus (SLE)