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Differential estimation of CKD using creatinine- versus cystatin C-based estimating equations by category of body
Suma Vupputuri1, Caroline S Fox, Josef Coresh
1Center for Health Research, Kaiser Permanente Georgia, Atlanta, GA 30305, USA. suma.vupputuri@kp.org
Insights
Body Mass Index (BMI) may affect chronic kidney disease (CKD) prevalence estimates derived from cystatin C-based equations. Higher BMI levels showed increased CKD prevalence when using cystatin C, unlike creatinine-based methods.
Area of Science:
- Nephrology
- Clinical Chemistry
- Epidemiology
Background:
- Adiposity is linked to elevated cystatin C levels.
- Cystatin C-based equations may overestimate chronic kidney disease (CKD) prevalence in individuals with higher Body Mass Index (BMI).
Purpose of the Study:
- To investigate the impact of Body Mass Index (BMI) on the prevalence estimates of stage 3 or 4 chronic kidney disease (CKD) using various cystatin C-based equations compared to creatinine-based equations.
Main Methods:
- Cross-sectional study of 6,709 US adults from the Third National Health and Nutrition Examination Survey.
- Defined normal weight, overweight, and obesity based on BMI (kg/m²).
- Calculated estimated glomerular filtration rate (eGFR) using creatinine-based (eGFR(MDRD)) and multiple cystatin C-based equations (eGFR(CysC,age,sex,race), eGFR(CysC), increased cystatin C, eGFR(Cr,CysC,age,sex,race)).
Main Results:
- Differences in stage 3 or 4 CKD prevalence between cystatin C-based and creatinine-based equations increased with higher BMI levels.
- Obese participants showed a 6.5% greater CKD prevalence with eGFR(CysC,age,sex,race) and a 9.5% greater prevalence with increased cystatin C compared to eGFR(MDRD).
- The equation incorporating both creatinine and cystatin C (eGFR(Cr,CysC,age,sex,race)) showed minimal differences in CKD prevalence across BMI categories.
Conclusions:
- Body Mass Index (BMI) significantly influences the estimated prevalence of stage 3 or 4 CKD when utilizing cystatin C-based equations.
- The findings suggest caution when interpreting cystatin C-based eGFR in individuals with varying BMI levels.
- Further research is needed to establish a gold-standard GFR measure across different adiposity levels.
Background:
Adiposity is associated with cystatin C. Cystatin C-based glomerular filtration rate (GFR) equations may result in overestimation of chronic kidney disease (CKD) prevalence at greater body mass index (BMI) levels.
Study Design:
Cross-sectional.
Setting & Participants:
6,709 US adult Third National Health and Nutrition Examination Survey participants.
Factor:
BMI.
Outcome:
Absolute percentage of difference in prevalence of stage 3 or 4 CKD between creatinine- and cystatin C-based estimating equations by level of BMI.
Measurements:
Normal weight, overweight, and obesity were defined as BMI of 18.5 to less than 25.0, 25 to less than 30.0, and 30 kg/m(2) or greater, respectively. Stage 3 or 4 CKD (estimated glomerular filtration rate [eGFR], 15 to 59 mL/min/1.73 m(2)) was defined using the 4-variable creatinine-based Modification of Diet in Renal Disease Study equation (eGFR(MDRD)); cystatin C level, age, sex, and race equation (eGFR(CysC,age,sex,race)); cystatin C-only equation (eGFR(CysC)); cystatin C level of 1.12 mg/L or greater (increased cystatin C); and an equation incorporating serum creatinine level, cystatin C level, age, sex, and race (eGFR(Cr,CysC,age,sex,race)).
Results:
Differences in stage 3 or 4 CKD prevalence estimates between eGFR(CysC,age,sex,race), eGFR(CysC), and increased cystatin C, separately, and eGFR(MDRD) were greater at higher BMI levels. Specifically, compared with estimates derived using eGFR(MDRD) for normal-weight, overweight, and obese participants, estimated prevalences of stage 3 or 4 CKD were 2.1%, 3.0%, and 6.5% greater when estimated by using eGFR(CysC,age,sex,race) (P trend = 0.005); 0.1%, 0.6%, and 2.2% greater for eGFR(CysC) (P trend = 0.03); 2.9%, 5.2%, and 9.5% greater for increased cystatin C (P trend < 0.001); and -0.1%, -0.4%, and 0.0% greater for eGFR(Cr,CysC,age,sex,race), respectively (P trend = 0.7).
Limitations:
No gold-standard measure of GFR was available.
Conclusions:
BMI may influence the estimated prevalence of stage 3 or 4 CKD when cystatin C-based equations are used.
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