title: Serum cystatin C is not an appropriate marker for kidney involvement in patients with primary Sjögren's syndrome.
abstract: OBJECTIVE
  We aimed to investigate serum cystatin C (cysC) levels in primary Sjögren's syndrome (pSS) patients, and evaluate its correlation with renal involment.
  
  
  METHODS
  Eighty-six pSS patients and 65 age- and gender-matched healthy controls were enrolled into the study. Serum cysC, urea, serum creatinine (SCr), creatinine clearance (CrCl), glomerular filtration rates (GFR), Na, K, Mg, Ca, uric acid, P, erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), anti-Ro/SS-A, anti-La/SS-B, antinuclear antibodies, 24-h urinary poteinuria and microalbuminuria were evaluated.
  
  
  RESULTS
  Mean serum cysC levels did not differ between the patients and healthy controls (P > 0.05). Nine patients with pSS had proteinuria over 150 mg (and microalbuminuria over 30 mg) per 24 h. In patients with proteinuria, serum cysC levels correlated with serum K (r = 0.279, P = 0.024), ESR (r = 0.405, P = 0.001) and the disease duration (r = 0.235, P = 0.04), respectively. Patients with positive anti-Ro/SS-A and anti-La/SS-B antibodies had higher SCr levels compared to those with negative serology (r = 0.292, P = 0.009, and r = 0.259, P = 0.022, respectively). Nine patients with proteinuria and anti-Ro/SS-A, anti-La/SS-B positivity tended to have lower K and Mg levels which suggests subclinical renal tubular acidosis.
  
  
  CONCLUSIONS
  There were no associations between serum cysC levels and renal involvement in patients with pSS. However, in patients with proteinuria, serum cysC levels were correlated with acute-phase reactants, suggesting an association with disease activity in terms of degree of inflammation.
authors.affiliation: Department of Nephrology, Ataturk Education and Research Hospital, Bilkent-Ankara, Turkey.
authors.forename: Alpaslan
authors.initials: A
authors.lastname: Altunoğlu
authors.affiliation: Department of Rheumatology, Faculty of Medicine, Yıldırım Beyazıt University, Ataturk Education and Research Hospital, Ankara, Turkey.
authors.forename: Şükran
authors.initials: Ş
authors.lastname: Erten
authors.affiliation: Department of Rheumatology, Şanlıurfa Education and Research Hospital, Şanlıurfa, Turkey.
authors.forename: Ali
authors.initials: A
authors.lastname: Şahin
authors.affiliation: Department of Biochemistry, Ataturk Education and Research Hospital, Ankara, Turkey.
authors.forename: Semra
authors.initials: S
authors.lastname: Işıkoğlu
authors.affiliation: Department of Biochemistry, Ataturk Education and Research Hospital, Ankara, Turkey.
authors.forename: Salim
authors.initials: S
authors.lastname: Neşelioğlu
authors.affiliation: Department of Internal Medicine, Diyarbakır Education and Research Hospital, Diyarbakır, Turkey.
authors.forename: Cahide
authors.initials: C
authors.lastname: Erzurum
authors.affiliation: Department of Biochemistry, Yıldırım Beyazıt University, Ataturk Education and Research Hospital, Ankara, Turkey.
authors.forename: Özcan
authors.initials: Ö
authors.lastname: Erel
mesh_terms: D000328:Adult; D000419:Albuminuria / Q000097:blood / Q000209:etiology; D015415:Biomarkers / Q000097:blood; D001799:Blood Sedimentation; D016022:Case-Control Studies; D055316:Cystatin C / Q000032:analysis*; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D007668:Kidney / Q000503:physiopathology; D007674:Kidney Diseases / Q000097:blood* / Q000175:diagnosis / Q000209:etiology / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D012859:Sjogren's Syndrome / Q000097:blood* / Q000150:complications / Q000175:diagnosis
chemical_list: D015415:Biomarkers; C525030:CST3 protein, human; D055316:Cystatin C
keywords: cystatin C; microalbuminuria; primary Sjögren's syndrome; proteinuria; renal involvement