title: Low complements and high titre of anti-Sm antibody as predictors of histopathologically proven silent lupus nephritis without abnormal urinalysis in patients with systemic lupus erythematosus.
abstract: OBJECTIVE
  The aim of this study was to clarify the clinical characteristics and predictors of silent LN (SLN), a type of LN in SLE without abnormal urinalysis or renal impairment.
  
  
  METHODS
  Of 182 patients who underwent renal biopsy, 48 did not present with abnormal urinalysis or renal impairment at the time of biopsy. The patients with LN (SLN group, n = 36) and those without LN (non-LN group, n = 12) were compared with respect to their baseline characteristics. Bivariate analysis comprised Fisher's exact test and the Mann-Whitney test, whereas multivariate analysis employed binomial logistic regression analysis.
  
  
  RESULTS
  LN was histopathologically identified in 36 of 48 patients. According to the International Society of Nephrology/Renal Pathology Society classification, 72% of the SLN patients were classified as having class I/II, with a further 17% having class III/IV. Bivariate analyses indicated that platelet count, serum albumin, complement components (C3 and C4), complement haemolytic activity (CH50), anti-Sm antibody titre and anti-ribonucleoprotein antibody titre were significantly different between groups. Multivariate analysis indicated that CH50 and C3 titres were significantly lower in the SLN group, whereas anti-Sm antibody titre was significantly higher. The cut-off titre, calculated based on the receiver operating characteristic curve for CH50, was 33 U/ml, with a sensitivity and specificity of 89% and 83%, respectively. The cut-off titre for anti-Sm antibodies was 9 U/ml, with a sensitivity and specificity of 74% and 83%, respectively.
  
  
  CONCLUSIONS
  Low titres of CH50 and C3 and a high titre of anti-Sm antibody were identified as predictors of SLN.
authors.affiliation: First Department of Internal Medicine, Second Department of Internal Medicine, School of Medicine, University of Occupational and Environmental Health and Department of Hematology, Clinical Immunology and Infectious Diseases, Ehime University Graduate School of Medicine, Matsuyama, Japan. First Department of Internal Medicine, Second Department of Internal Medicine, School of Medicine, University of Occupational and Environmental Health and Department of Hematology, Clinical Immunology and Infectious Diseases, Ehime University Graduate School of Medicine, Matsuyama, Japan.
authors.forename: Jun
authors.initials: J
authors.lastname: Ishizaki
authors.affiliation: First Department of Internal Medicine, Second Department of Internal Medicine, School of Medicine, University of Occupational and Environmental Health and Department of Hematology, Clinical Immunology and Infectious Diseases, Ehime University Graduate School of Medicine, Matsuyama, Japan.
authors.forename: Kazuyoshi
authors.initials: K
authors.lastname: Saito
authors.affiliation: First Department of Internal Medicine, Second Department of Internal Medicine, School of Medicine, University of Occupational and Environmental Health and Department of Hematology, Clinical Immunology and Infectious Diseases, Ehime University Graduate School of Medicine, Matsuyama, Japan.
authors.forename: Masao
authors.initials: M
authors.lastname: Nawata
authors.affiliation: First Department of Internal Medicine, Second Department of Internal Medicine, School of Medicine, University of Occupational and Environmental Health and Department of Hematology, Clinical Immunology and Infectious Diseases, Ehime University Graduate School of Medicine, Matsuyama, Japan.
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Mizuno
authors.affiliation: First Department of Internal Medicine, Second Department of Internal Medicine, School of Medicine, University of Occupational and Environmental Health and Department of Hematology, Clinical Immunology and Infectious Diseases, Ehime University Graduate School of Medicine, Matsuyama, Japan.
authors.forename: Mikiko
authors.initials: M
authors.lastname: Tokunaga
authors.affiliation: First Department of Internal Medicine, Second Department of Internal Medicine, School of Medicine, University of Occupational and Environmental Health and Department of Hematology, Clinical Immunology and Infectious Diseases, Ehime University Graduate School of Medicine, Matsuyama, Japan.
authors.forename: Norifumi
authors.initials: N
authors.lastname: Sawamukai
authors.affiliation: First Department of Internal Medicine, Second Department of Internal Medicine, School of Medicine, University of Occupational and Environmental Health and Department of Hematology, Clinical Immunology and Infectious Diseases, Ehime University Graduate School of Medicine, Matsuyama, Japan.
authors.forename: Masahito
authors.initials: M
authors.lastname: Tamura
authors.affiliation: First Department of Internal Medicine, Second Department of Internal Medicine, School of Medicine, University of Occupational and Environmental Health and Department of Hematology, Clinical Immunology and Infectious Diseases, Ehime University Graduate School of Medicine, Matsuyama, Japan.
authors.forename: Shintaro
authors.initials: S
authors.lastname: Hirata
authors.affiliation: First Department of Internal Medicine, Second Department of Internal Medicine, School of Medicine, University of Occupational and Environmental Health and Department of Hematology, Clinical Immunology and Infectious Diseases, Ehime University Graduate School of Medicine, Matsuyama, Japan.
authors.forename: Kunihiro
authors.initials: K
authors.lastname: Yamaoka
authors.affiliation: First Department of Internal Medicine, Second Department of Internal Medicine, School of Medicine, University of Occupational and Environmental Health and Department of Hematology, Clinical Immunology and Infectious Diseases, Ehime University Graduate School of Medicine, Matsuyama, Japan.
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Hasegawa
authors.affiliation: First Department of Internal Medicine, Second Department of Internal Medicine, School of Medicine, University of Occupational and Environmental Health and Department of Hematology, Clinical Immunology and Infectious Diseases, Ehime University Graduate School of Medicine, Matsuyama, Japan. tanaka@med.uoeh-u.ac.jp.
authors.forename: Yoshiya
authors.initials: Y
authors.lastname: Tanaka
mesh_terms: D000328:Adult; D000888:Antibodies, Anti-Idiotypic / Q000097:blood*; D015415:Biomarkers / Q000097:blood; D001706:Biopsy; D003176:Complement C3 / Q000378:metabolism; D003181:Complement C4 / Q000378:metabolism; D015941:Complement Hemolytic Activity Assay; D003165:Complement System Proteins / Q000378:metabolism*; D005260:Female; D006801:Humans; D007668:Kidney / Q000473:pathology / Q000503:physiopathology; D008180:Lupus Erythematosus, Systemic / Q000150:complications* / Q000503:physiopathology / Q000652:urine*; D008181:Lupus Nephritis / Q000097:blood / Q000175:diagnosis* / Q000209:etiology*; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D012044:Regression Analysis; D012680:Sensitivity and Specificity; D016482:Urinalysis; D055517:snRNP Core Proteins / Q000276:immunology*
chemical_list: D000888:Antibodies, Anti-Idiotypic; D015415:Biomarkers; D003176:Complement C3; D003181:Complement C4; D055517:snRNP Core Proteins; D003165:Complement System Proteins
keywords: anti-Sm antibody; complement; silent lupus nephritis; systemic lupus erythematosus