TY - JOUR
T1 - Performance of Glomerular Filtration Rate Estimating Equations Before and After Bariatric Surgery
AU - Chang, Alex R.
AU - George, Jason
AU - Levey, Andrew S.
AU - Coresh, Josef
AU - Grams, Morgan E.
AU - Inker, Lesley A.
N1 - Funding Information:
Alex R. Chang, MD, MS, Jason George, MD, Andrew S. Levey, MD, Josef Coresh, MD, PhD, Morgan E Grams, MD, PHD, and Lesley A. Inker, MD, MS. Research idea: ARC; study design: ARC, ASL, JC, MEG, LAI; data acquisition: JG; data analysis/statistical analysis: ARC, MEG; interpretation: all authors; supervision or mentorship: MEG, LAI. Each author contributed important intellectual content during manuscript drafting or revision and accepts accountability for the overall work by ensuring that questions to the accuracy or integrity of any portion of the work are appropriately investigated and resolved. Research was supported by National Institutes of Health/National Institute of Diabetes and Digestive and Kidney Diseases grants K23 DK106515-01 and R01DK097020. The funders had no role in study design; data collection, analysis, or reporting; or the decision to submit for publication. The authors declare that they have no relevant financial interests. An abstract of this research was presented at ASN Kidney Week 2019, November 9, 2019, Washington D.C. Deidentified data may be available on reasonable request. Received March 5, 2020. Evaluated by 2 external peer reviewers and a statistician, with editorial input from an Acting Editor-in-Chief (Editorial Board Member Vianda S. Stel, PhD). Accepted in revised form August 21, 2020. The involvement of an Acting Editor-in-Chief to handle the peer-review and decision-making processes was to comply with Kidney Medicine's procedures for potential conflicts of interest for editors, described in the Information for Authors & Journal Policies.
Funding Information:
Research was supported by National Institutes of Health / National Institute of Diabetes and Digestive and Kidney Diseases grants K23 DK106515-01 and R01DK097020 . The funders had no role in study design; data collection, analysis, or reporting; or the decision to submit for publication.
Publisher Copyright:
© 2020 The Authors
PY - 2020/11/1
Y1 - 2020/11/1
N2 - Rationale & Objective: Evaluation of glomerular filtration rate (GFR) is challenging in adults undergoing bariatric surgery because creatinine and cystatin C levels are influenced by changes in muscle and fat mass. Additionally, indexing of GFR by body surface area (BSA) may by affected by decreases in BSA. Study Design: Prospective observational study. Setting & Participants: 27 adults with body mass index (BMI) ≥ 35 kg/m2 who underwent measurement of GFR before and after bariatric surgery. Outcomes: Indexed and nonindexed GFRs measured (mGFRs) using plasma iohexol clearance, indexed and nonindexed estimated GFR (eGFR) based on levels of creatinine, cystatin C, or both from Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations. Analytic Approach: Bias and percent of estimates within 20% and 30% of mGFR (P20 and P30) for estimating equations were examined. Results: Mean presurgery BMI was 49.5 (SD, 9.4) kg/m2, BSA was 2.42 (SD, 0.27) m2, nonindexed mGFR was 117.3 (SD, 34.1) mL/min, and indexed mGFR was 84.1 (SD, 22.0) mL/min/1.73 m2. After 6 months, mean BMI changed by –13.8 (95% CI, −15.9 to −11.8) kg/m2, BSA by −0.30 (95% CI, −0.33 to −0.27) m2, and nonindexed mGFR by −9.2 (95% CI, −17.2 to −1.1) mL/min, while indexed mGFR was unchanged at 5.1 (95% CI, −0.1 to 10.4) mL/min/1.73 m2. Nonindexed eGFRcr was unbiased (median bias, 5.0 [95% CI, −4.3 to 11.6] mL/min) before surgery, but overestimated mGFR (8.8 [95% CI, 1.8 to 16.9] mL/min) after surgery. Nonindexed eGFRcys underestimated mGFR before (median bias, −12.1 [95% CI, −21.4 to −1.2] mL/min) and after surgery (−11.2 [95% CI, −21.8 to −7.3] mL/min). Nonindexed eGFRcr-cys was unbiased before (median bias, −6.0 [95% CI, −11.0 to 1.0] mL/min) and after surgery (−2.0 [95% CI, −8.8 to 4.9] mL/min). Findings were similar for indexed eGFR compared with indexed mGFR. Limitations: Small, mostly white sample. Conclusions: Changes in indexed and nonindexed GFRs may be discordant after bariatric surgery in adults because of decreases in BSA. Indexed and nonindexed eGFRcr-cys may be less biased than indexed or nonindexed eGFRcr or eGFRcys because of opposite biases in estimating mGFR.
AB - Rationale & Objective: Evaluation of glomerular filtration rate (GFR) is challenging in adults undergoing bariatric surgery because creatinine and cystatin C levels are influenced by changes in muscle and fat mass. Additionally, indexing of GFR by body surface area (BSA) may by affected by decreases in BSA. Study Design: Prospective observational study. Setting & Participants: 27 adults with body mass index (BMI) ≥ 35 kg/m2 who underwent measurement of GFR before and after bariatric surgery. Outcomes: Indexed and nonindexed GFRs measured (mGFRs) using plasma iohexol clearance, indexed and nonindexed estimated GFR (eGFR) based on levels of creatinine, cystatin C, or both from Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations. Analytic Approach: Bias and percent of estimates within 20% and 30% of mGFR (P20 and P30) for estimating equations were examined. Results: Mean presurgery BMI was 49.5 (SD, 9.4) kg/m2, BSA was 2.42 (SD, 0.27) m2, nonindexed mGFR was 117.3 (SD, 34.1) mL/min, and indexed mGFR was 84.1 (SD, 22.0) mL/min/1.73 m2. After 6 months, mean BMI changed by –13.8 (95% CI, −15.9 to −11.8) kg/m2, BSA by −0.30 (95% CI, −0.33 to −0.27) m2, and nonindexed mGFR by −9.2 (95% CI, −17.2 to −1.1) mL/min, while indexed mGFR was unchanged at 5.1 (95% CI, −0.1 to 10.4) mL/min/1.73 m2. Nonindexed eGFRcr was unbiased (median bias, 5.0 [95% CI, −4.3 to 11.6] mL/min) before surgery, but overestimated mGFR (8.8 [95% CI, 1.8 to 16.9] mL/min) after surgery. Nonindexed eGFRcys underestimated mGFR before (median bias, −12.1 [95% CI, −21.4 to −1.2] mL/min) and after surgery (−11.2 [95% CI, −21.8 to −7.3] mL/min). Nonindexed eGFRcr-cys was unbiased before (median bias, −6.0 [95% CI, −11.0 to 1.0] mL/min) and after surgery (−2.0 [95% CI, −8.8 to 4.9] mL/min). Findings were similar for indexed eGFR compared with indexed mGFR. Limitations: Small, mostly white sample. Conclusions: Changes in indexed and nonindexed GFRs may be discordant after bariatric surgery in adults because of decreases in BSA. Indexed and nonindexed eGFRcr-cys may be less biased than indexed or nonindexed eGFRcr or eGFRcys because of opposite biases in estimating mGFR.
KW - Bariatric surgery
KW - CKD-EPI
KW - body surface area
KW - creatinine
KW - cystatin C
KW - filtration markers
KW - glomerular filtration rate
KW - obesity
KW - weight loss
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U2 - 10.1016/j.xkme.2020.08.008
DO - 10.1016/j.xkme.2020.08.008
M3 - Article
C2 - 33319195
AN - SCOPUS:85094622319
SN - 2590-0595
VL - 2
SP - 699-706.e1
JO - Kidney Medicine
JF - Kidney Medicine
IS - 6
ER -