title: Cystatin C-Creatinine Based Glomerular Filtration Rate Equation in Obese Chronic Kidney Disease Patients: Impact of Deindexation and Gender.
abstract: Cystatin C is considered an alternative to creatinine to estimate glomerular filtration rate (GFR). However, studies have reported that increased adiposity is associated with a higher level of circulating cystatin C questioning the performance of estimation of GFR using cystatin C in obese subjects.
  
  
  
  We prospectively included 166 obese stages 1-5 chronic kidney disease (CKD) patients between 2013 and 2015. GFR was measured with a reference method without (measured GFR [mGFR]) and with adjustment to body surface area (mGFRr) and estimated (eGFR) or de-indexed eGFR using the Chronic Kidney Disease and Epidemiology (CKD-EPI) equation using creatinine (CKD-EPIcreat), cystatin (CKD-EPIcyst) and the combination of cystatin and creatinine (CKD-EPIcyst-creat).
  
  
  
  The biases between mGFR and de-indexed CKD-EPIcyst-creat were significantly lower than de-indexed CKD-EPIcreat (p = 0.001). Accuracies were significantly better with de-indexed CKD-EPIcyst-creat compared to CKD-EPIcreat and CKD-EPIcyst, respectively (p = 0.04 and 0.03). Bland and Altman plot showed a great dispersion of all formulae when patients had a GFR >60 ml/min. Interestingly, there is a gender difference; biases, precisions and accuracies of de-indexed CKD-EPIcyst-creat were significantly lower in obese women. These results may be related to a difference in the change of body composition during obesity in men versus women and in fact only waist circumference (WC) was positively and significantly correlated with cystatin C (p < 0.0001) whereas body mass index (BMI; p = 0.3) was not; bias for CKD-EPIcyst-creat was related with WC.
  
  
  
  Cystatin C-creatinine-based GFR equations outperform creatinine-based formula in obese CKD patients especially those with BMI ≥35 and in obese women.
authors.affiliation: Service d'Exploration Fonctionnelle Rx00E9;nale, Hx00F4;pital Edouard Herriot, Hospices Civils de Lyon, INSERM U1060, CarMeN, Lyon, France.
authors.forename: Sandrine
authors.initials: S
authors.lastname: Lemoine
authors.forename: Marine
authors.initials: M
authors.lastname: Panaye
authors.forename: Caroline
authors.initials: C
authors.lastname: Pelletier
authors.forename: Chantal
authors.initials: C
authors.lastname: Bon
authors.forename: Laurent
authors.initials: L
authors.lastname: Juillard
authors.forename: Laurence
authors.initials: L
authors.lastname: Dubourg
authors.forename: Fitsum
authors.initials: F
authors.lastname: Guebre-Egziabher
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003404:Creatinine / Q000097:blood*; D055316:Cystatin C / Q000097:blood*; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000097:blood* / Q000150:complications; D011446:Prospective Studies; D051436:Renal Insufficiency, Chronic / Q000097:blood* / Q000150:complications; D055815:Young Adult
chemical_list: D055316:Cystatin C; D003404:Creatinine