title: Estimation of glomerular filtration rate in hospitalised patients: are we overestimating renal function?
abstract: QUESTIONS UNDER STUDY AND PRINCIPLES: Estimating glomerular filtration rate (GFR) in hospitalised patients with chronic kidney disease (CKD) is important for drug prescription but it remains a difficult task. The purpose of this study was to investigate the reliability of selected algorithms based on serum creatinine, cystatin C and beta-trace protein to estimate GFR and the potential added advantage of measuring muscle mass by bioimpedance.
  
  
  METHODS
  In a prospective unselected group of patients hospitalised in a general internal medicine ward with CKD, GFR was evaluated using inulin clearance as the gold standard and the algorithms of Cockcroft, MDRD, Larsson (cystatin C), White (beta-trace) and MacDonald (creatinine and muscle mass by bioimpedance).
  
  
  RESULTS
  69 patients were included in the study. Median age (interquartile range) was 80 years (73-83); weight 74.7 kg (67.0-85.6), appendicular lean mass 19.1 kg (14.9-22.3), serum creatinine 126 μmol/l (100-149), cystatin C 1.45 mg/l (1.19-1.90), beta-trace protein 1.17 mg/l (0.99-1.53) and GFR measured by inulin 30.9 ml/min (22.0-43.3). The errors in the estimation of GFR and the area under the ROC curves (95% confidence interval) relative to inulin were respectively: Cockcroft 14.3 ml/min (5.55-23.2) and 0.68 (0.55-0.81), MDRD 16.3 ml/min (6.4-27.5) and 0.76 (0.64-0.87), Larsson 12.8 ml/min (4.50-25.3) and 0.82 (0.72-0.92), White 17.6 ml/min (11.5-31.5) and 0.75 (0.63-0.87), MacDonald 32.2 ml/min (13.9-45.4) and 0.65 (0.52-0.78).
  
  
  CONCLUSIONS
  Currently used algorithms overestimate GFR in hospitalised patients with CKD. As a consequence eGFR targeted prescriptions of renal-cleared drugs, might expose patients to overdosing. The best results were obtained with the Larsson algorithm. The determination of muscle mass by bioimpedance did not provide significant contributions.
authors.affiliation: Service of Nephrology, Ospedale Carità, Locarno, Switzerland.
authors.forename: Michelle
authors.initials: M
authors.lastname: Frank
authors.forename: Sara
authors.initials: S
authors.lastname: Guarino-Gubler
authors.forename: Michel
authors.initials: M
authors.lastname: Burnier
authors.forename: Marc
authors.initials: M
authors.lastname: Maillard
authors.forename: Franco
authors.initials: F
authors.lastname: Keller
authors.forename: Luca
authors.initials: L
authors.lastname: Gabutti
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D003404:Creatinine / Q000097:blood*; D055316:Cystatin C / Q000097:blood*; D017097:Electric Impedance; D005919:Glomerular Filtration Rate; D006801:Humans; D007297:Inpatients / Q000706:statistics & numerical data; D019746:Intramolecular Oxidoreductases / Q000097:blood*; D054834:Lipocalins / Q000097:blood*; D018482:Muscle, Skeletal / Q000033:anatomy & histology; D011446:Prospective Studies; D012372:ROC Curve; D051436:Renal Insufficiency, Chronic / Q000097:blood / Q000503:physiopathology*; D015203:Reproducibility of Results; D013557:Switzerland
chemical_list: D055316:Cystatin C; D054834:Lipocalins; D003404:Creatinine; D019746:Intramolecular Oxidoreductases; C022466:prostaglandin R2 D-isomerase