The vertical widths of the bands represent proportions of individuals in (left axis) eGFR categories according to the 2009 equation, (right axis) eGFR categories according to the 2021 equation, and (middle) proportions belonging to connected left and right axis groups. Classifications use the Kidney Disease: Improving Global Outcomes CKD G classifications, based on eGFR, as follows: G1 or G2, 60 mL/min/1.73 m2 or greater; G3a, 45 to 59 mL/min/1.73 m2; G3b, 30 to 44 mL/min/1.73 m2; G4, 15 to 29 mL/min/1.73 m2; and G5, less than 15 mL/min/1.73 m2.
eAppendix. Supplementary Methods
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Walther CP, Winkelmayer WC, Navaneethan SD. Updated US Prevalence Estimates for Chronic Kidney Disease Stage and Complications Using the New Race-Free Equation to Estimate Glomerular Filtration Rate. JAMA Netw Open. 2022;5(2):e220460. doi:10.1001/jamanetworkopen.2022.0460
Estimating glomerular filtration rate (eGFR) from serum creatinine is common in medicine. The 2009 Chronic Kidney Disease–Epidemiology Collaboration (CKD-EPI) equation uses age, sex, race (Black vs non-Black), and creatinine level. Concerns were raised that the use of race in estimating GFR could contribute to care inequities.1 CKD-EPI recently derived an equation for eGFR from serum creatinine level without a race coefficient, the adoption of which is recommended by a national task force.2,3 Validity of CKD staging using eGFR thresholds (ie, CKD G stages) is in part supported by CKD-related complications at more severe stages.4 Changes in G stage with the new equation could affect diagnosis and treatment for many persons. We investigated US population changes in CKD G stage and in 4 CKD-related complications, comparing the race-free serum creatinine–based 2021 CKD-EPI equation with the 2009 equation.
In this cross-sectional study, we used data from the US National Health and Nutrition Examination Survey (NHANES 2011-2018). NHANES was approved by the National Center for Health Statistics research ethics review board, and participants gave written informed consent. This analysis used publicly available deidentified data and was not considered human participant research per Baylor College of Medicine institutional review board policy. Appropriate survey methods were used.5 This cross-sectional study followed the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) reporting guideline.
We included NHANES participants aged 20 years and older and classified them by self-reported race into Black vs non-Black groups (Mexican American, other Hispanic, non-Hispanic Asian, non-Hispanic White, and other race, including multiracial, ie, the categories used in the 2009 equation). We calculated eGFR using serum creatinine–based CKD-EPI equations (2009 and 2021); G stage6 was calculated for eGFRs of less than 60 mL/min/1.73 m2. Anemia was defined as hemoglobin level of less than 12 g/dL in female participants and less than 13 g/dL in male participants (to convert hemoglobin to grams per liter, multiply by 10.0), acidosis as serum bicarbonate levels of 22 mEq/L or lower (to convert to millimoles per liter, multiply by 1), hyperphosphatemia as serum phosphate levels of 4.5 mg/dL or greater, and hypertension as systolic blood pressure of 140 mm Hg or greater or diastolic blood pressure of 90 mm Hg or greater. Multiple imputation was performed for missing laboratory values (creatinine was missing in 10.3% of participants). Analyses were performed with Stata version 14.2 (StataCorp). Additional details are in the eAppendix in the Supplement.
Overall, 39 156 individuals participated in NHANES 2011-2018. An estimated 18.1 (95% CI, 16.6-19.6) million adults had an eGFR of less than 60 ml/min/1.73 m2 using either equation. The mean (SD) age was 71 (13) years, and an estimated 10.5 (95% CI, 9.5-11.6) million were female. An estimated 5.5 (95% CI, 4.9-6.2) million adults were reclassified in G stage with the 2021 equation: 1.0 (95% CI, 0.8-1.2) million into a more severe stage and 4.5 (95% CI, 3.8-5.2) million into a less severe stage. All persons reclassified into more severe stages self-reported as Black, and all persons reclassified into less severe stages self-reported as non-Black. Of all Black adults, 3.9% (95% CI, 3.3%-4.4%) were recategorized into a more severe stage (Figure). Of all non-Black adults, 2.2% (95% CI, 1.9%-2.5%) were recategorized into a less severe stage. CKD-related complications are shown in the Table.
Transitioning from the 2009 equation to the 2021 equation resulted in more than 5 million US adults changing CKD G stage classification, mostly in moderate CKD stages (between eGFR >60 mL/min/1.73 m2 and CKD stage G3a, ie, eGFR 45-59 mL/min/1.73 m2). The 2021 equation increased the prevalence of eGFR less than 60 mL/min/1.73 m2 among Black persons by 2.9 percentage points (7.1% to 9.9%), larger than the 2 percentage points reported using 1999 to 2002 NHANES data.2 The decrease in the prevalence of eGFR less than 60 mL/min/1.73 m2 among individuals identifying as non-Black of 1.6 percentage points (7.5% to 5.9%) was similar to that observed in 1999 to 2002 data.2 The prevalence estimates of CKD complications were qualitatively similar in reclassified and adjacent nonreclassified groups.
Limitations include use of single laboratory measurements. Limited numbers in some subgroups prevented precise estimates, including of complications, and prevented separate analysis of smaller racial and ethnic groups. Cystatin C levels are not available for these years.
In this study, estimation of eGFR using the 2021 CKD-EPI equation resulted in substantial reclassification in CKD G stage in US adults. However, CKD-related complication prevalence estimates were not substantially altered.
Accepted for Publication: January 7, 2022.
Published: February 15, 2022. doi:10.1001/jamanetworkopen.2022.0460
Open Access: This is an open access article distributed under the terms of the CC-BY License. © 2022 Walther CP et al. JAMA Network Open.
Corresponding Author: Carl P. Walther, MD, MS, Selzman Institute for Kidney Health, Section of Nephrology, Department of Medicine, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030 (email@example.com).
Author Contributions: Dr Walther had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.
Concept and design: All authors.
Acquisition, analysis, or interpretation of data: All authors.
Drafting of the manuscript: Walther, Navaneethan.
Critical revision of the manuscript for important intellectual content: All authors.
Statistical analysis: Walther.
Administrative, technical, or material support: Winkelmayer, Navaneethan.
Conflict of Interest Disclosures: Dr Winkelmayer reported receiving personal fees from Akebia/Otsuka, AstraZeneca, Bayer, Boehringer Ingelheim and Eli Lilly and Co, Janssen Pharmaceuticals, Merck, Pharmacosmos, Reata, and Relypsa outside the submitted work. Dr Navaneethan reported receiving personal fees from Bayer, Boehringer Ingelheim and Eli Lilly and Co, Vifor, and Tricida; receiving grants from Keryx; and receiving research funding from the Department of Veterans Affairs Health Services Research & Development outside the submitted work. No other disclosures were reported.
Funding/Support: Dr Walther is supported by grant K23DK122131 from the National Institute of Diabetes and Digestive and Kidney Diseases.
Role of the Funder/Sponsor: The funder had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication.
Disclaimer: The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health or Veterans Administration.