title: [Practical markers of renal function in cystinosis patients].
abstract: BACKGROUND
  Cystinosis is an autossomic recessive systemic disease that leads to renal insufficiency early in life unless cysteamine be started early. Unfortunately, even in this situation the patients will develop chronic renal disease with need of renal replacement therapy about second decade of life. Therefore, the renal function evaluation is essential to these patients. The aim of this study was to evaluate cystatin C, serum creatinine and creatinine clearance estimated by stature (Schwartz Formula) in cystinosis patients, with different degrees of renal function, and to correlate these parameters.
  
  
  METHODS
  We studied cystinosis patients, aged lower than 18 years, with different degrees of renal function, classified according to KDOQI in Chronic Kidney Disease stage 1 to 4. No patient was under renal replacement therapy. In these patients we evaluate the serum creatinine, cystatin C and creatinine clearance according to Schwartz Formula.
  
  
  RESULTS
  We analyzed 103 blood samples of 26 patients. We detected a significant statistical correlation between serum creatinine and cystatin C (r = 0.81, p < 0.0001), cystatin C and creatinine clearance estimated by stature (r = -0.84, p < 0.0001) and between serum creatinine and creatinine clearance estimated by stature (r = -0.97, p < 0.0001).
  
  
  CONCLUSIONS
  The expensive measurement of cystatin C showed no advantage in relation to serum creatinine and creatinine clearance according to Schwartz Formula in cystinosis patients to estimate the glomerular filtration rate. This is the first report checking the value of serum creatinine, creatinine clearance estimated by stature and cystatin C in cystinosis patients.
authors.affiliation: Instituto da Criança, HCFMUSP.
authors.forename: Luciana Pache de Faria
authors.initials: LP
authors.lastname: Guimaraes
authors.forename: Letícia Aparecida Lopes
authors.initials: LA
authors.lastname: Neri
authors.forename: Nairo Massakasu
authors.initials: NM
authors.lastname: Sumita
authors.forename: Maria Helena
authors.initials: MH
authors.lastname: Vaisbich
mesh_terms: D015415:Biomarkers / Q000032:analysis; D003404:Creatinine / Q000097:blood*; D055316:Cystatin C / Q000097:blood*; D003554:Cystinosis / Q000097:blood* / Q000503:physiopathology*; D006801:Humans; D007677:Kidney Function Tests
chemical_list: D015415:Biomarkers; D055316:Cystatin C; D003404:Creatinine