title: Serum cystatin C is independently associated with renal impairment and high sensitivity C-reactive protein in systemic lupus erythematosus.
abstract: OBJECTIVE
  In systemic lupus erythematosus (SLE) patients, glomerular ﬁltration rate (GFR) is usually estimated using the modiﬁed Cockcroft-Gault (mCG) and Modiﬁcation of Diet in Renal Disease (MDRD) equations. We aimed to study cystatin C (sCysC) in SLE to assess its agreement with standard renal indices and investigate factors affecting sCysC in SLE.
  
  
  METHODS
  SLE patients (≥4 ACR criteria) and healthy women from Greater Manchester were recruited and clinical assessments were undertaken. SCysC was measured using R & D Systems' ELISA. Agreement between renal measures was assessed using Deming plots and factors associated with sCysC in SLE were examined by multiple linear regression analyses.
  
  
  RESULTS
  178 patients and 68 controls had median (IQR) ages of 53 (46-61) and 50 (39-60) years, respectively. In an age-adjusted analysis, SLE patients had higher sCysC (1.16 [0.98-1.36] vs. 0.950 [0.73-1.13] mg/l; p<0.0001) and within SLE those with a history of lupus nephritis had higher sCysC (1.31 [1.10-1.66] vs. 1.11 [0.95-1.29] mg/l; p<0.005). SCysC correlated positively with serum creatinine, and inversely to renal measures (r=-0.530; p<0.0001 [mCG], and r=-0.620; p<0.0001 [MDRD]). There was closer agreement between the two eGFR measures than between either eGFR measures and sCysC. In addition to age and serum creatinine, a multivariate analysis (β, p) found that high-sensitivity C-reactive protein (hs-CRP) (0.03, 0.026) was also independently associated with sCysC in SLE.
  
  
  CONCLUSIONS
  In SLE, sCysC may be influenced by low grade inﬂammation as well as by renal dysfunction. Therefore, SCysC should not supplant current assessment of renal dysfunction in SLE.
authors.affiliation: The Kellgren Centre for Rheumatology, Central Manchester Foundation Trust, Manchester, UK. c.chew@nhs.net
authors.forename: Christine
authors.initials: C
authors.lastname: Chew
authors.forename: Philip W
authors.initials: PW
authors.lastname: Pemberton
authors.forename: Awal Al-M
authors.initials: AA
authors.lastname: Husain
authors.forename: Sahena
authors.initials: S
authors.lastname: Haque
authors.forename: Ian N
authors.initials: IN
authors.lastname: Bruce
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000097:blood; D002097:C-Reactive Protein / Q000032:analysis*; D016022:Case-Control Studies; D003404:Creatinine / Q000097:blood; D003430:Cross-Sectional Studies; D055316:Cystatin C / Q000097:blood*; D004739:England; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D007668:Kidney / Q000378:metabolism / Q000503:physiopathology*; D016014:Linear Models; D008180:Lupus Erythematosus, Systemic / Q000097:blood / Q000175:diagnosis* / Q000276:immunology / Q000503:physiopathology; D008181:Lupus Nephritis / Q000097:blood / Q000175:diagnosis* / Q000276:immunology / Q000503:physiopathology; D008875:Middle Aged; D015999:Multivariate Analysis; D011237:Predictive Value of Tests; D011379:Prognosis
chemical_list: D015415:Biomarkers; C525030:CST3 protein, human; D055316:Cystatin C; D002097:C-Reactive Protein; D003404:Creatinine