title: Estimated Glomerular Filtration Rate in Renal Transplantation: The Nephrologist in the Mist.
abstract: BACKGROUND
  Formulas do not estimate renal function with acceptable precision and accuracy.
  
  
  METHODS
  We compared 51 creatinine-based and/or cystatin c-based formulas with a gold standard (iohexol plasma clearance) in 193 renal transplant recipients using concordance correlation coefficient, total deviation index, coverage probability and the error in chronic kidney disease (CKD) stage classification.
  
  
  RESULTS
  No formula showed a concordance correlation coefficient greater than 0.90 (average for creatinine-based formulas: ∼0.70 and for cystatin c-based formulas: ∼0.85). A wide total deviation index was observed: approximately 70% (creatinine-based) and approximately 50% (cystatin c-based), indicating that 90% of the estimations showed bounds of error of ±70% or ±50%, respectively, compared with the gold standard. No formula included 90% of the estimations within a coverage probability of ±10%. Half the CKD stages classified by creatinine-based formulas were incorrect, mainly due to overestimation of renal function. One of 3 CKD stages diagnosed by cystatin c-based formulas was incorrect, with both overestimation and underestimation. Overall, the formulas showed very low precision and accuracy and a high degree of error in reflecting real renal function.
  
  
  CONCLUSIONS
  In conclusion, formulas do not properly reflect renal function in kidney transplantation, which makes their use in clinical practice unreliable. Moreover, their use in clinical trials should be avoided.
authors.affiliation: 1 Centre for Biomedical Research of the Canary Islands (CIBICAN). University of La Laguna, Tenerife, Spain. 2 Department of Nephrology, University Hospital of the Canary Islands, Tenerife, Spain. 3 Department of Anatomic Pathology, Faculty of Medicine at the University of La Laguna, Tenerife, Spain. 4 Department of Clinical Pharmacology, University Hospital of the Canary Islands, Tenerife, Spain. 5 Istituto di Ricerche Farmacologiche Mario Negri, Clinical Research Center for Rare Diseases "Aldo e Cele Daccò", Ranica (BG), Italy. 6 Clinical Analysis Laboratory, University Hospital Marqués de Valdecilla, Santander, Spain. 7 Fundación Canaria Rafael Clavijo para la Investigación Biomédica, Tenerife, Spain. 8 Research Unit, University Hospital of the Canary Islands, Tenerife, Spain.
authors.forename: Sergio
authors.initials: S
authors.lastname: Luis-Lima
authors.forename: Domingo
authors.initials: D
authors.lastname: Marrero-Miranda
authors.forename: Ana
authors.initials: A
authors.lastname: González-Rinne
authors.forename: Armando
authors.initials: A
authors.lastname: Torres
authors.forename: José M
authors.initials: JM
authors.lastname: González-Posada
authors.forename: Aurelio
authors.initials: A
authors.lastname: Rodríguez
authors.forename: Eduardo
authors.initials: E
authors.lastname: Salido
authors.forename: Ana
authors.initials: A
authors.lastname: Aldea-Perona
authors.forename: Flavio
authors.initials: F
authors.lastname: Gaspari
authors.forename: Fabiola
authors.initials: F
authors.lastname: Carrara
authors.forename: Juan A
authors.initials: JA
authors.lastname: Gómez-Gerique
authors.forename: Natalia
authors.initials: N
authors.lastname: Negrín-Mena
authors.forename: Lourdes
authors.initials: L
authors.lastname: Pérez-Tamajón
authors.forename: Federico
authors.initials: F
authors.lastname: González-Rinne
authors.forename: Hugo
authors.initials: H
authors.lastname: Jiménez-Hernández
authors.forename: Alejandro
authors.initials: A
authors.lastname: Jiménez-Sosa
authors.forename: Esteban
authors.initials: E
authors.lastname: Porrini
mesh_terms: D003430:Cross-Sectional Studies; D005260:Female; D005500:Follow-Up Studies; D005919:Glomerular Filtration Rate / Q000502:physiology*; D006085:Graft Survival / Q000502:physiology*; D006801:Humans; D007677:Kidney Function Tests; D016030:Kidney Transplantation; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D051436:Renal Insufficiency, Chronic / Q000503:physiopathology* / Q000601:surgery; D066027:Transplant Recipients