title: Removal of body surface area normalisation improves raw-measured glomerular filtration rate estimation by the Chronic Kidney Disease Epidemiology Collaboration equation and drug dosing in the obese.
abstract: OBJECTIVE
  We aimed to compared estimated glomerular filtration rate (eGFR) according to the Chronic Kidney Disease Epidemiology Collaboration equation (CKD-EPI), with (mL/min/1.73 m(2) ) and without body surface area (BSA) normalisation (CKD-EPI_noBSA, mL/min) against measured (99m) Technetium - diethylenepentaacetic acid (Tc-DTPA GFR) (mL/min) in 222 individuals, including 80 with malignancy.
  
  
  METHODS
  BSA was calculated for each individual using the Du Bois equation. The CKD-EPI and CKD-EPI_noBSA equations were compared with measured Tc-DTPA GFR with respect to bias, proportion within 30% of GFR (P30) and root mean square error for predicting levels of GFR, and concordance in relation to carboplatin dosing.
  
  
  RESULTS
  The mean (SD) for BSA and measured GFR for the entire group was 1.99 (0.25) m(2) and 127 (41) mL/min respectively. The P30 for Tc-DTPA GFR was significantly higher with the CKD-EPI_noBSA (80%) than with the CKD-EPI equation (63%, P = 0.0001). In those with body mass index (BMI) > 30 kg/m(2) , the P30 values for the CKD-EPI_noBSA and CKD-EPI were 74% and 42% respectively (P < 0.0001). Carboplatin dosing concordance for the cancer patients using the CKD-EPI and CKD-EPI_noBSA equation was 71% and 56% respectively (P = 0.07). In 78 individuals with BMI > 30 kg/m(2) , concordance in relation to carboplatin dosing using CKD-EPI_noBSA was 65% compared with 26% with the CKD-EPI (P < 0.0001).
  
  
  CONCLUSIONS
  The CKD-EPI without normalisation (CKD-EPI_noBSA) equation was superior to the CKD-EPI equation in estimating raw-measured Tc-DTPA GFR (mL/min).
authors.affiliation: Clinical Biochemistry Unit, Canterbury Health Laboratories, Christchurch, New Zealand.|Pathology, University of Otago, Christchurch, New Zealand.
authors.forename: J S C
authors.initials: JS
authors.lastname: Chew-Harris
authors.affiliation: Medicine, University of Otago, Christchurch, New Zealand.|Department of Clinical Pharmacology, Christchurch Hospital, Christchurch, New Zealand.
authors.forename: P K L
authors.identifier: http://orcid.org/0000-0002-5470-5191
authors.initials: PK
authors.lastname: Chin
authors.affiliation: Clinical Biochemistry Unit, Canterbury Health Laboratories, Christchurch, New Zealand.|Pathology, University of Otago, Christchurch, New Zealand.
authors.forename: C M
authors.initials: CM
authors.lastname: Florkowski
authors.affiliation: Clinical Biochemistry Unit, Canterbury Health Laboratories, Christchurch, New Zealand.|Pathology, University of Otago, Christchurch, New Zealand.
authors.forename: P
authors.initials: P
authors.lastname: George
authors.affiliation: Medicine, University of Otago, Christchurch, New Zealand.|Prince of Wales Hospital, Sydney, Australia.
authors.forename: Z
authors.initials: Z
authors.lastname: Endre
mesh_terms: D000328:Adult; D000368:Aged; D015992:Body Mass Index; D001830:Body Surface Area; D016190:Carboplatin / Q000493:pharmacokinetics*; D005919:Glomerular Filtration Rate / Q000502:physiology*; D006801:Humans; D008875:Middle Aged; D009765:Obesity / Q000378:metabolism*; D051436:Renal Insufficiency, Chronic / Q000378:metabolism*; D016284:Technetium Tc 99m Pentetate / Q000378:metabolism; D055815:Young Adult
chemical_list: D016190:Carboplatin; D016284:Technetium Tc 99m Pentetate
keywords: CKD-EPI; body surface area; creatinine; drug dosing; eGFR; obese