title: Cystatin C: A Promising Marker of Renal Function in Patients with Systemic Lupus Erythematosus?
abstract: OBJECTIVE
  Cystatin C has a higher correlation with glomerular filtration rate and a more significant clinical prognosis than creatinine. We sought to determine whether it is a marker of renal function different from creatinine (cystatin C potentially superior to creatinine), in patients with systemic lupus erythematosus.
  
  
  METHODS
  37 patients with systemic lupus erythematosus were evaluated. Serum cystatin C was determined by nephelometry and creatinine by modified Jaffe method. We compared five formulas: Chronic Kidney Disease â Epidemiology Collaboration cystiatin; Chronic Kidney Disease â Epidemiology Collaboration creatinine-cystatin; Cockcroft-Gault; Modification of Diet in Renal Disease and Chronic Kidney Disease â Epidemiology Collaboration creatinine, using the latter as a reference. We analyzed the influence of clinical and laboratory factors in cystatin C variation, using multivariate linear regression.
  
  
  RESULTS
  Cystatin C was singly elevated in ten participants, versus none isolated creatinine elevation, and this difference was significant (p = 0.002). There was a difference between the estimated glomerular filtration rate by Chronic Kidney Disease â Epidemiology Collaboration cystatin and by Chronic Kidney Disease â Epidemiology Collaboration creatinine (-6.0541 mL/min/1.73 m², p = 0.07), more pronounced for lower glomerular filtration rate. Consequently, Chronic Kidney Disease â Epidemiology Collaboration cystatin reclassified 4 patients as having chronic kidney disease de novo and 1 patient as not having chronic kidney disease (p = 0.375). Cystatin C was only significantly influenced by age (p < 0.001).
  
  
  CONCLUSIONS
  Several reports showed cystatin C as a better marker to define chronic kidney disease, allowing more accurate classification and risk stratification, compared with creatinine. In this study, Cystatin C revealed as a promisor marker of renal function in patient with lupus, mainly in patients with lower glomerular filtration rates. The correlation between age and cystatin C seems to be a confounding factor, as glomerular filtration rate physiologically declines with ageing.
  
  
  CONCLUSIONS
  Cystatin C was potentially superior to creatinine and in this study and cystatin C seems to detect changes in glomerular filtration rate earlier than creatinine and may be a better screening method for chronic kidney disease in systemic lupus erythematosus.
authors.affiliation: Serviço de Medicina I. Centro Hospitalar Lisboa Norte. Lisboa. Portugal.
authors.forename: Lígia
authors.initials: L
authors.lastname: Peixoto
authors.affiliation: Serviço de Medicina I. Centro Hospitalar Lisboa Norte. Lisboa. Portugal.
authors.forename: Patrício
authors.initials: P
authors.lastname: Aguiar
authors.affiliation: Faculdade de Medicina. Universidade de Lisboa. Lisboa. Portugal.
authors.forename: Raquel
authors.initials: R
authors.lastname: de Bragança
authors.affiliation: Serviço de Medicina I. Centro Hospitalar Lisboa Norte. Lisboa. Portugal.
authors.forename: Joana Rosa
authors.initials: JR
authors.lastname: Martins
authors.affiliation: Serviço de Medicina I. Centro Hospitalar Lisboa Norte. Lisboa. Portugal.
authors.forename: Alba Janeiro
authors.initials: AJ
authors.lastname: Acabado
authors.affiliation: Serviço de Medicina I. Centro Hospitalar Lisboa Norte. Lisboa. Portugal. Faculdade de Medicina. Universidade de Lisboa. Lisboa. Portugal.
authors.forename: José Luís
authors.initials: JL
authors.lastname: Ducla-Sores
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015415:Biomarkers / Q000097:blood; D003404:Creatinine / Q000097:blood*; D003430:Cross-Sectional Studies; D055316:Cystatin C / Q000097:blood*; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D007668:Kidney / Q000503:physiopathology*; D008180:Lupus Erythematosus, Systemic / Q000097:blood* / Q000150:complications / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D051436:Renal Insufficiency, Chronic / Q000097:blood / Q000209:etiology; D055815:Young Adult
chemical_list: D015415:Biomarkers; D055316:Cystatin C; D003404:Creatinine